Dietary choices have profound effects on overall health. Beyond supplying the body with nutrients including proteins, vitamins, and minerals, nutrition is now considered an important factor for influencing disease risk, triggering health conditions, and offering medicinal and protective qualities.1 In medicine, evidence-based nutritional advice is part of the gold standard for common diseases such as obesity, diabetes mellitus, hyperlipidemia, and coronary heart disease.2 However, the impact of nutrition on the progression of dermatological diseases is not similarly regarded as dietary modifications have been underappreciated in terms of dermatological disease therapy. Recent studies, however, have uncovered significant evidence that well-substantiated dietary interventions can influence the course of skin diseases. In learning more about these nutritional recommendations, dermatologists can be more comprehensive in their treatment recommendations to better care for their patients.
On the macro level, the GI tract absorbs nutrients from food, and the circulatory system passes them on to other parts of the body. On the micro level, the gut hosts microbiota comprising prokaryotic and eukaryotic symbiotic microorganisms which support the host in terms of metabolic and immune function. They can metabolize indigestible complex polysaccharides into essential nutrients, protect the host by maintaining the gut’s epithelial barrier integrity, and influence immune system development.3–6 Communication between the microbiota and the host is important for preventing harm to the host, which includes preventing tissue-damaging inflammatory responses and avoiding infection or uncontrolled growth.3 Communication is possible via hormone-like compounds produced by the microbiota: short chain fatty acids (SCFAs), secondary bile acids, cortisol, and neurotransmitters including gamma-aminobutyric acid (GABA), serotonin, dopamine, and tryptophan.7–9 These compounds can locally affect the intestinal mucosal barrier, enter the bloodstream, and thus can impose systemic effects at distant organs and systems as well. These compounds, interacting with skin receptors, can consequently directly affect the skin or modify the skin’s commensal bacteria.7
The gut and skin are connected through the systemic circulation, where these two systems can communicate via the diet, microbial metabolites, the immune system, neuroendocrine pathways, and the central nervous system. The skin-gut axis is termed from the gut and skin communicating with one another via these gut microbiota metabolite products.10 Host lifestyle factors including diet and hygiene can impact the proportions of commensal microbiota strains and disrupt mucosal immunological tolerance.10 If the gut microbiota is perturbed, the quantity of microbial products can change and impact the host accordingly.10–12 Therefore, an imbalance in gut microbiome, termed intestinal dysbiosis, can affect skin function and integrity through their metabolic activity and immunological impact.13–15 The dysbiotic state is characterized by an impaired gut barrier, including an imbalanced gut microbiome, reduced mucus layer, intestinal permeation into the bloodstream, and gut inflammation.8 Specifically, certain neurotransmitters such as GABA, dopamine, serotonin, acetylcholine, as well as short chain fatty acids such as butyrate have important effects such as creation of a robust intestinal barrier with decreased permeability. Absorption of short chain fatty acids is dependent on intake of fiber, intestinal absorptive capacity, and fermentation rate of microbes.10 Compromise of these factors can lead to decreased short chain fatty acid absorption and decreased epithelial barrier strength. Molecules with potential modulatory effect on the skin and gut are summarized in Table 1. Additionally, dysbiosis leading to inflammatory skin disease is seen in conditions such as acne vulgaris where a decrease in Firmicutes and an increase in Bacteroides bacteria is observed per literature.10
SCFAs (short chain fatty acids)
From fermentation of dietary complex carbohydrates by colonic bacteria
Anti-inflammatory effects; promotes keratinocyte differentiation14,16
Gamma-aminobutyric acid (GABA)
Bacterial by-product
Anti-itch, anti-inflammatory, anti-allergy11,12,17,18
Dopamine
Bacterial by-product
Inhibits human hair growth12,19
Phenol and p-cresol
Metabolites of aromatic amino acids produced by colonic bacteria
Disrupts skin barrier integrity and epidermal differentiation, reduces skin hydration, disrupts keratinization20
Serotonin
Anti-inflammatory11
Catechins: a polyphenol compound
Green tea
Anti-inflammatory, reductions in pro-inflammatory eicosanoids, novel therapeutics for treatment of melanoma21–24
Polyphenols: chemical compounds found naturally in plants. Protect plants from damage caused by ultraviolet radiation from the sun. These are poorly absorbed from the small intestine, and therefore accumulate in the large intestine. Polyphenols then catalyze changes in the gut microbiome that lead to significantly lower levels of inflammation.
Strawberries, blueberries, plums, cherries, apples, black currants, black olives, dark chocolate, black tea, coffee, hazelnuts, pecans, turmeric, cloves, cinnamon, ginger, cumin
Anti-inflammation, anti-oxidant25,26
Lycopene
Tomatoes
Protection against photodamage27,28
Alpha-lipoic acid
Organ meat (liver, kidney), broccoli, spinach, tomatoes, brussels sprouts, rice bran
Antioxidant, Anti-aging29,30
Prolamin
Wheat, rye, barley
Protection against atopic dermatitis31
Dietary changes play a role in consequent modulation of the gut microbiome, hormonal changes, and neurotransmitter activity which can lead to a wide variety of dermatological disorders, systemic disease, and health outcomes. In regard to alterations of gut microbiome, with nutrient deficiencies, dermatological manifestations are familiar. For example, inadequate protein intake can result in Kwashiorkor, an exfoliative erythroderma dermatitis, while vitamin B3 deficiency, or Pellagra, can lead to a photo-distributed dermatitis.32 Conversely, nutrient excess may also elicit dermatological manifestations. For example, hypervitaminosis A can manifest with xerosis, cheilitis, and alopecia while insulin resistance and hyperinsulinemia can present as acanthosis nigricans and skin tags.33 In some cases, dietary interventions may even serve as an aspect of prevention. Alpha-lipoic acid, found in certain meats and vegetables, can prevent glycation seen in the aging process, and a diet rich in fruits and vegetables can reduce the risk of cancer.34
In this article, we review common skin disorders and the current literature on the effect of different diets and offer evidence-based nutritional guidance for the everyday practicing dermatologist. The reviewed skin disorders, including acne, atopic dermatitis, hidradenitis suppurativa, and psoriasis are the most common skin conditions clinicians treat.
A systematic search of PubMed, EMBASE, and Cochrane Central Registrar was conducted between January 1st, 1985 and December 31st 2023 to identify studies to treat dietary intervention among different diseases. Search terms broadly included the disease of interest (“acne,” “hidradenitis suppurativa,” “psoriasis,” “atopic dermatitis” [OR] “eczema”) [AND] (“gut,” “diet,” “supplement,” “inflammation”). Case reports, clinical trials, controlled studies, comparative studies, systematic reviews, and meta-analyses were included. After abstract and title review followed by full-text article review, 46, 9, 39, and 10 articles in the English language were included for acne, hidradenitis suppurativa, psoriasis, and atopic dermatitis respectively. Systematic reviews and meta-analyses were included for reference review. PRISMA flow diagrams for acne, hidradenitis suppurativa, psoriasis, and atopic dermatitis can be seen in Figures 1-4. Level of evidence for included studies was defined as I: systematic reviews of randomized controlled trials, II: RCTs or observational studies with dramatic effect, III: non-randomized controlled cohort/follow-up studies, IV: case series, case-control studies, or historically controlled studies, and V: mechanism-based reasoning. This systematic review did not require IRB approval. The study is registered with PROSPERO and followed PRISMA guidelines.
Acne vulgaris, a chronic inflammatory skin disease affecting 85% of adolescent individuals globally is influenced by hormonal factors, genetics, diet, stress, and environmental factors. Notably, the prevalence of this dermatological disease can vary across different regions and populations with studies showing increased prevalence and incidence in westernized versus non-westernized societies.35,36
On the skin surface, disruption of the normal skin flora can contribute to acne pathogenesis. However when looking at the gut-skin axis, increased intestinal permeability and disruptions in the gut microbiota can lead to acne through systemic inflammation.37 Stress disturbs eubiosis, and bacteria
The systematic review search revealed many cross-sectional studies which used questionnaires to assess diet and its impact on acne in populations such as Turkey, China, Korea, Italy, India, USA, Pakistan, and Norway. A systematic review of diet and acne shows acne being linked to diet. While overall positive associations exist between acne and familial dysmetabolism, high body mass indices, and family history of acne, further research is needed to evaluate the true impact of diet on acne.42,43 A systematic review consisting of 34 articles concluded that a high glycemic index diet and high glycemic load was positively associated with increased acne severity.44 Diets rich in refined carbohydrates, saturated fat, and trans-fats stimulate the synthesis of sebum triglycerides, promoting the growth of
With the positive association of high glycemic index, diets and acne, several studies have evaluated the impact of a low-glycemic index diet on acne. These studies have shown significant reductions in noninflammatory and inflammatory lesion counts, smaller sebaceous glands, decreased inflammation, and reduced acne severity grading.50–54
Diets such as the Mediterranean diet, emphasize consumption of components such as fish and olive oil which contain omega-3 fatty acids, vegetables such as leafy greens, fruits, nuts, whole grains with a moderate consumption of dairy products as well as a decreased consumption of red meat and processed foods. Omega-3 fatty acids show a protective effect towards acne with an association with decreased sebum production and inhibition of inflammatory cytokines, reducing inflammatory acne lesions.35,55–58 An epidemiological study found that participants who consumed large amounts of fish and seafood, rich in omega-3 fatty acids, had less oily skin and fewer acne lesions.35
Based on how omega-3 fatty acids as a part of the Mediterranean diet are associated with less acneiform lesions, it can be theorized that fish oil supplements, rich in omega-3 fatty acids, may be beneficial for acne. However, only a few studies have been conducted to evaluate this effect. Smaller studies have concluded moderate improvement in acne lesions with supplementation, however the efficacy of fish oil supplementation may depend on the acne severity.59–61
In addition, when looking at the gut-skin axis, the use of probiotics as a potential therapy has been considered. The clinical trials completed with oral probiotics have shown positive results.38–42,62 Oral probiotics are theorized to modify the intestinal microbiota, generating an anti-inflammatory response and restoring intestinal integrity, or through metabolic pathways involving insulin-like growth factor I (IGF-1).63–68 A few specific strains shown to be associated with improvement in acne symptom severity include
There have also been several randomized controlled trials which evaluate other supplements. Chan et al evaluates lactoferrin with vitamin E and zinc supplementation, which was seen to reduce acneiform lesion counts.69 Tolino et al evaluated a combination of probiotics, vitamin E, zinc, and nicotinamide with either male or female formulations, which also had significant response.70 Other supplements studied include vitamin D, vitamin A, berberis vulgaris fruit extract, magnesium, phosphate, herbal syrups, coenzyme Q10, green tea extract, sunflower seeds, soy isoflavones, and more.71–80 (See Table 2)
19
IV
Case study of 5 patients with mild to moderate acne vulgaris
Daily dietary supplementation of 250 mg of EPA obtained from sardines and anchovies, 3.75 mg of zinc gluconate, 50 mcg of selenium, 50 mcg of chromium and 50 mg of EGCG from green tea extract for 2 months
Total lesions count; inflammatory lesions count
Both average total and inflammatory lesion counts decreased significantly
Dietary supplementation with PUFAs may improve acne lesion count
20
II
Observational study of 1200 Kitavan patients
Acne incidence and prevalence
Of the 1200 Kitavan subjects, no cases of acne were observed. Of 115 Aché subjects, over 843 days, no case of acne were observed
The incidence of acne between nonwesternized and westernized societies can have a genetic difference, however Ache and Kitavan diets also differ from typical Western high-glycemic diets in that they are composed of minimally processed plant and animal foods. Low-glycemic load dietary interventions may have therapeutic potential in treating acne
21
IV
Case-control study to assess gut microbiota of 8 acne patients
Oral minocycline
DNA extracted from stool samples and facial skin swabs before and after minocycline treatment
After minocycline treatment, patients had a decreased Firmicutes to Bacteroides ratio
Minocycline induces gut and skin microbiota derangements
22
IV
Case-control study on 43 acne patients with matched controls
Intestinal microbiota
Acne patients have lower Firmicutes and higher Bacteroidiain microbials
Acne patients have gut microbial dysbiosis
23
IV
Case-control study on 8 acne patients with 8 matched controls
Minocycline
Bacterial community profiling
A lower Firmicutes to Bacteroides ratio was associated with a Western diet and with acne; the ratio was significantly reduced following antibiotics in the Asian population
Race and diet have a significant impact on the Firmicutes to Bacteroides ratio in acne patients taking antibiotics
24
IV
Case-control of 31 acne patients with 31 controls
Gut microbiota evaluation through 16S RNA Sequencing
In acne patients, Actinobacteria is decreased and Proteobacteria is increased
Shows a link between gut microbiota changes and acne risk
25
IV
Cross-sectional, case-control study of 43 acne patients and 43 matched controls
Gut microbiota analysis of 16SrDNA and microbial metabolites
Men with acne had lower abundance of 18 types of microbes, and had disordered metabolism of fatty acids. Female acne patients had increased Clostridium and declined Oscillibacter and Odoribacterin, and showed dysbiosis of amino acid metabolism
Gut dysbiosis in acne patients are gender-specific
26
I
Systematic review of 53 articles meeting eligibility criteria
There is growing interest in acne and diet, with acne-promoting factors to include high glycemic index/load foods, dairy, fatty foods, and chocolate
Further research is needed for a more comprehensive outline of the effect of diet on acne
27
I
Systematic review of acne epidemiology, distribution, and causes on Medline and Embase to the end of November 2011
Acne is associated with pre-puberty, a positive family history, and a possible association between dairy food intake and diet
28
I
Of 410 articles in the literature search, 34 articles met the inclusion criteria in the literature search
High glycemic index and load was positively associated with increased acne severity
Increased carbohydrate intake and higher glycemic load and index have increased acnegenic effect.
29
II
Randomized cross-over study of 46 children in Ulaanbaatar and 28 children in Boston
Daily whole milk or low-fat milk
Plasma hormone levels
Mongolian children had higher growth hormone levels
Milk intake may stimulate endogenous growth hormone production
30
I
Systematic review, meta-analysis of 14 studies consisting of 78,529 patients, including 23,046 acne patients and 55,483 controls
Increased risk for acne was seen with full-fat dairy, any milk, whole milk, low-fat/skim milk, cheese, and yogurt consumption
Any dairy is associated with an increased odds ratio for acne
31
IV
Case reports of 5 male patients
Stopping whey protein supplementation
Total acneiform lesions
Acneiform lesions cleared in 4 patients after discontinuation of whey protein
Whey protein may promote acne formation
32
II
Observational study of 30 patients
Protein calorie supplements
Onset or exacerbation of acneiform lesions
Those consuming protein calorie supplements, specifically Whey protein extract, had a significant onset of acneiform lesions
This type of supplementation may worsen acne
33
IV
Case series of 6 patients
Whey protein exposure
Acne lesion count
These patients developed truncal acne after consumption of whey protein
This trending supplement may be related to truncal acne
34
II
Randomized controlled cohort study of 43 male acne patients
Low glycemic-index load diet
Acneiform lesion count, insulin sensitivity, androgen and testosterone levels
Experimental diet resulted in greater reduction in weight, less total acne lesion counts, and improved insulin sensitivity
A low-glycemic-load diet can improve acne and insulin sensitivity
35
II
Randomized controlled trial of 43 male acne patients
Low glycemic-index load diet with the control group having a high glycemic-load diet
Changes in lesion counts, sex hormone binding globulin, free androgen index, insulin-like growth factor-I, and insulin-like growth factor binding proteins
Experimental diet resulted in reduced weight, reduced free androgen index, and increased insulin-like growth factor binding protein
Nutrition-related lifestyle factors help in acne pathogenesis
36
II
Randomized controlled trial of 32 mild to moderate acne patients with a low glycemic load diet
Histopathological examination of skin samples
Experimental diet showed significant improvement in the number of acne lesions, reduced inflammation, and reduced sebaceous gland size
Reduction in glycemic load diet can lead to improvements in acne
37
II
Observational study with 2,995 respondents
41-item, IRB-approved, anonymous, web-based questionnaire to assess low glycemic South Beach, Florida diet
Most patients noted improvements in their acne condition within 3 months of starting the low-glycemic South Beach, Florida diet
The South Beach Diet could be an additional modality in which to treat acne
38
II
Randomized trial of 58 adolescent males.
High or Low glycemic index diets.
Severity of facial inflammatory lesions, body mass index
Differences between the groups were not significant during the 8-week period
A longer time frame and or weight loss may be necessary to further evaluate acne among adolescent males
39
IV
Case control study of 93 cases and 200 controls
Food-frequency questionnaire
Mediterranean diet showed protective effects against acne; familial hypercholesterolemia, diabetes, and hypertension are strong risk factors for acne
Acne patients were more likely to have familial dysmetabolism history. The Mediterranean diet may play a role in the pathogenesis of acne
40
IV
Case-control study of 40 acne patients and 40 control patients
Adherence to the Mediterranean diet
Global evaluation acne severity score, and PREDIMED (Prevención con Dieta Mediterránea) questionnaire to assess adherence to the Mediterranean diet
Significant negative correlation between the severity of acne and the adherence to Mediterranean diet
It is important to consider a holistic approach for acne management
41
IV
Cross sectional, case control study of 35 patients
Adherence to the Mediterranean diet
IGF-1 serum levels
IGF-1 serum levels were higher in the western diet group compared to the Mediterranean group
The Mediterranean diet can have a protective role in acne pathogenesis through IGF-1
42
IV
Case-control study of 51 acne patients and 51 matched controls
Global acne grading system score, PREDIMED (Prevención con Dieta Mediterránea) questionnaire, and body composition
Higher percentage of acne patients had lower Mediterranean diet adherence scores and higher values of fat mass in their body composition
Diet and body composition may be useful in assessing clinical severity of acne
43
IV
Case-cohort study of 13 males with inflammatory acne
Three capsules of fish oil daily for 12 weeks, which contained a total of 930 mg of EPA, 720 mg DHA, and 174 mg DPA
Total inflammatory lesions counts and acne severity grades were determined using the Allen and Smith grading scale; skin redness data obtained using a Konica Minolta CR-400 colorimeter with the L*a*b* color system as defined by the Commission Internationale de L’Eclairage
Inconclusive results, as eight patients showed improved acne, four patients showed worsened acne, and one patient's acne remained unchanged
Fish oil supplementation to improve acne may be dependent on the initial acne severity
44
II
Randomized, double-blind prospective study of 45 patients with mild to moderate acne
Three groups, one which took 2000 mg of EPA and DHA daily, the second group taking borage oil containing 400 mg GLA daily, and a control group not receiving any treatment for 10 weeks
Inflammatory lesion count and non-inflammatory lesion count
Both treatment groups showed a significant decrease in both inflammatory and non-inflammatory acne lesion count
Moderate doses of omega-3 polyunsaturated fatty acids or gamma-linoleic acids could improve acne lesions
45
I
Systematic review of 38 studies
Report benefits for omega-3 fatty acid supplementation in treatment of acne among other dermatologic disorders
Shows well-studied benefits of omega-3 fatty acid supplementation in dermatology
46
II
RCT of 18 patients in the treatment group, 18 patients in the placebo group
Fermented milk with 200 mg of lactoferrin daily
Acne lesion counts and grade
The lactoferrin group showed improvement with significant decreases in inflammatory lesion count, decreased sebum content specifically surface triacylglycerols
Lactoferrin-enriched fermented milk may help treat acne vulgaris through a mechanism of decreasing surface triacylglycerols
47
II
Prospective, open-label randomized study with 45 female participants
Treatment group A receiving probiotic supplementation, group B receiving minocycline, and group C receiving both probiotic and minocycline
Clinical and subjective assessments
The treatment group receiving both the probiotic and the antibiotic had a significant decrease in total lesion counts compared to the other groups at 8 and 12 weeks
Probiotics in adjunct with antibiotics may provide a synergistic anti-inflammatory effect
48
RCT of 20 subjects with acne
Supplementation with the probiotic strain Lactobacillus rhamnosus SP1 compared with placebo group which received a liquid lacking probiotic
Paired skin biopsy analysis for insulin-like growth factor 1, and forkhead box protein O1 gene expression involved in insulin signaling
Patients who had taken the probiotic had improved acneiform lesions compared to the placebo group, and had reduced insulin signaling expression
Supplementation with probiotic strain may improve appearance of adult acne
49
III
Non-randomized controlled cohort study of 30 patients
Supplement composed of biotin and 3 strains of lactic ferments in addition to a topical gel composed of azelaic acid, hydroxy pinacolone retinoate, and α-hydroxy acids
Photographic evaluation; GAGS (Global Acne Grading System) Score; SEBUTAPEtm score to assess seborrhea, measurement of the trans epidermal water loss (TEWL), and TBlue test on saliva to measure oxidative stress
Total reduction in the GAGS, SEBUTAPEtm, and TEWL score
Probiotic supplementation in adjunction with topical therapy may help treat acne
50
II
Randomized clinical trial of 44 subjects
Lactobacillus rhamnosus T12 dietary supplement
Dermatological visual score of acne, and instrumental evaluations including hydration, pH, etc
The Lactobacillus supplement group showed a significant improvement in acne appearance and instrumental skin evaluations
Data supports the use of Lactobacillus containing supplements in diseases such as seborrheic dermatitis and acne
51
I
Systematic review of 697 articles
Further studies are needed to evaluate the full effects of probiotics
52
II
Randomized control study of 14 patients per group
Lactobacillus plantarum CJLP55 ingestion or placebo
Acne lesion count and grade, skin sebum, hydration, pH and surface lipid assessment; Metagenomic DNA analysis on urine extracellular vesicles (reflecting systemic bacterial flora)
Those who ingested the supplement had improved acne lesion count and grade, and decreased sebum triglycerides. The supplement also decreased the Bacteroides: Firmicutes ratio
Dietary supplementation with this Lactobacillus strain was beneficial to the skin and gut microbiomes of acne patients
53
II
Randomized clinical trial with 168 participants
Lactoferrin with vitamin E and zinc
Reduction in the number of acne lesions
The intervention group showed a significant reduction in total lesion count
A twice daily supplement of lactoferrin with vitamin E and zinc may reduce acne lesion count in acne patients
54
II
Randomized clinical trial
Oral supplements contain biotin, probiotic, vitamin E, zinc, nicotinamide with the male formulation containing beta sitosterol and Boswellia serrata, and females containing myo-inositol and folic acid compared to topical cream device containing active plant agents (verbascoside, Ocimum gratissimum) and keratolytic molecules (salicylic acid, gluconolactone, complex alpha-hydroxy acids)
Global acne Grading System (GAGs)
Most patients had significant therapeutic response
An association of oral therapeutic supplementation for mild to moderate acne
55
I
Randomized clinical trial with 100 acne patients and 100 controls
0.25 micrograms of alfacalcidol daily
Serum levels of 25-hydroxy-vitamin D
Serum levels of 25-hydroxy-vitamin D were significantly lower in acne patients and were inversely correlated to acne severity. After the intervention, patients had significantly higher serum levels with decreased inflammatory markers IL6 and TNFα
Acne patients may have vitamin D deficiency, and alfacalcidol supplementation may have a beneficial role in acne treatment
56
I
Meta analysis from 1931 to 2021 regarding use of vitamin A in acne treatment, resulting in 9 studies for review
Of the 9 studies, 8 noted improvement in patients' acne with vitamin A supplementation
Oral vitamin A could serve as a therapy for acne management; however side effects must be considered
57
II
Randomized clinical trial of 49 patients
600 mg dried barberry
Counts of acne lesions, Michaelson's acne severity score
At 4 weeks, acne lesion count and acne severity score declined significantly in the intervention group
Barberry can be considered an effective supplemental treatment for acne patients
58
II
Randomized control study of 257 patients in the treatment arm, and 275 patients in the control arm
Dietary supplementation with magnesium, phosphate, omega 6 (linoleic acid calcium salt - C18:2 fatty acid Ca salt), and omega 7 (palmitoleic acid calcium salt - C16:1 fatty acid Ca salt) compared with controls who took isotretinoin
Acne resolution
All patients who took the dietary supplement reported complete regression of symptoms after 6 months of treatment. In the control group, 68% reported complete resolution of symptoms over the same period
The dietary supplementation can promote better regression and or cure of acne symptoms compared to drugs such as isotretinoin
59
II
Randomized clinical trial of 57 patients in each group
Herbal syrup consisting of Prunus domestica L., Tamarindus indica L., Terminalia chebula L., Ziziphus jujube L., and Cassia fistula (Plum, Jujube, Yellow Myrobalan, Golden Shower, Tamarind, Honey) or placebo
Acne severity index and Cardiff acne disability index
From 6 to 12 weeks, there was a significant reduction in the mean number of comedones in the herbal syrup intervention group
The herbal syrup could be an alternative treatment for acne
60
II
Randomized trial of 36 patients with acne
Treatment group received tretinoin 0.025% cream and once-daily coenzyme Q10 supplementation; placebo group only received tretinoin cream treatment
Serum glutathione peroxidase levels and severity of acne
Administration of coenzyme Q10 with tretinoin cream significantly improved acne severity after 8 weeks compared to tretinoin cream only. Serum glutathione peroxidase levels were not significant
Coenzyme Q10 supplementation may improve acne severity
61
II
Randomized clinical trial of 80 participants
1500 mg of decaffeinated green tea extract, or placebo of cellulose daily
Inflammatory lesion counts, fasting glucose levels, and lipid profile
No significant differences between the groups for total lesion counts, however improved acne lesion counts on the nose, perioral area, and chin in the treatment group
Green tea extract may improve lesion counts in certain areas, however more research is needed for total benefit of green tea extract on acne
62
II
Randomized controlled trial of 40 acne patients
Intervention group consumed 25 g sunflower-containing food daily for 7 days, control group were asked to stop eating sunflower seeds
10% increase/decrease in baseline acne severity index
Global acne grading score was not significantly different between groups. A majority of those taking the sunflower food supplement had at least a 10% increase in baseline acne severity
Sunflower seed intake may worsen acne severity
663
II
Randomized test of 25 patients
5 groups: isoflavones 40 mg, 80 mg, 120 mg, 160 mg and placebo, and treated for 4 weeks
Acne lesions
There was significant difference in acne lesions when comparing pre and post-treatment in groups receiving isoflavone supplementation
Soy isoflavones supplementation can lower total acneiform lesions
64
II
Randomized test of 40 patients
2 groups, placebo group and 160 mgs of isoflavone group
Acne lesions
There was significant difference after treatment with 160 mgs of isoflavone compared to placebo
Supplementation with 160 mg of soybean isoflavone can reduce total acneiform lesions
Hidradenitis suppurativa (HS), also known as acne inversa, is a chronic inflammatory skin disorder that causes skin abscesses and sinus tracts in intertriginous regions and has a poorly understood mechanism. HS can cause significant pain, disfigurement, and unpleasant odor, frequently resulting in social isolation and diminished quality of life.81–84
Numerous research studies have sought to characterize the cutaneous microbiome in individuals with HS. A systematic review conducted in 2022 identified several studies revealing common patterns, such as an overgrowth of anaerobic bacteria and a reduction in skin commensals, which typically exhibit antimicrobial properties. Two prevalent bacterial skin species,
Changes in gut microbiomes may stimulate inflammation and modify immune responses in HS. HS has been correlated with an elevated risk of inflammatory bowel disease.87 In a 2022 study, McCarthy et al reported an increased presence of
Elevated rates of obesity and metabolic syndrome are reported among HS patients, with higher BMI correlated with more severe disease activity.82,89,90 The connection between obesity and HS is attributed to increased mechanical friction, the development of humid microenvironments in skin folds fostering bacterial growth, and systemic low-grade inflammation.83,91 Despite these associations, engaging in exercise can be challenging and painful, perpetuating a cycle wherein exacerbated symptoms may decrease physical activity.
Interventions focused on weight loss have been demonstrated to alleviate HS disease flares. Documented instances of reduced HS severity following weight loss have been observed post-bariatric surgery.89,92,93 Kroman et al reported a 35% reduction in patients reporting HS symptoms after weight loss, a decrease in the mean number of involved sites from 1.93 to 1.22, and a significant association between weight loss exceeding 15% and reduced disease severity.89
Dietary modifications may play a role in managing HS. Barrea et al found that HS patients displayed poorer body composition and lower adherence to Mediterranean diets compared to healthy controls. In their cross-sectional, case-controlled observational study, HS patients consumed higher quantities of simple carbohydrates, total fat, and foods with a higher n-6/n-3 PUFA ratio. The severity of HS, assessed through the Sartorius score, showed an inverse correlation with adherence to the MedD.94 Although Lorite-Fuentes et al found a similar correlation of greater MedD adherence with lower HS severity,95 Velluzzi et al did not observe a significant association.96
Reducing carbohydrate and dairy consumption has been associated with improved HS symptoms. In an online anonymous survey study from 2020, 237/728 patients identified HS symptom-exacerbating foods, which included sweets (67.9%), bread/pasta/rice (51.1%), dairy (50.6%), and high-fat foods (44.2%).97 In an online survey study from 2022, individuals reported significant improvements in symptoms when adhering to Paleo and anti-inflammatory diets, which are characterized by reduced emphasis on dairy and grains and increased fruit and vegetable consumption. Reductions in sugar and dairy consumption were noted to lead to greater self-reported symptom improvement.98 In a small uncontrolled study, Danby reported that 39 out of 47 patients (83%) showed improvement under dairy-free diets, with none experiencing worsening symptoms. However, Danby’s study has faced criticism for lacking specificity in self-reported improvements regarding symptoms, potential response bias, and lack of formal or validated assessment methods.99
High intake of simple carbohydrates and dairy is theorized to increase follicular obstruction in HS.99 Casein, whey, natural androgens, and their precursors contribute to the blockage of follicles by inducing cytokeratin overexpression, keratinocyte hyperproliferation, and heightened follicular wall cornification, leading to the leakage and rupture of pilosebaceous units. Moreover, androgen hormones are hypothesized to play a role in activating HS.100 Casein activates insulin-like growth factor 1 (IGF-1), and whey increases insulin levels; hyperinsulinemia and high IGF-1 can amplify androgen receptor activation.99,101
Evidence suggests that brewer’s yeast and wheat may exacerbate HS symptoms. Anti-Saccharomyces cerevisiae antibodies (ASCA), traditionally considered specific for Crohn’s disease, have been found in elevated levels in patients with other autoimmune conditions such as type 1 diabetes and systemic lupus erythematosus.102 Assan et al reported that ASCA is associated with systemic inflammation and advanced HS disease.103
Elimination diets targeting wheat and brewer’s yeast have demonstrated effectiveness in stabilizing HS. In a study involving 12 patients with ASCA antibodies, a 12-month brewer’s yeast-free diet combined with surgical excision resulted in symptom stabilization, regression of skin lesions, and improvements in quality of life. Recurrence was observed upon accidental or intentional ingestion of beer or other foods containing wheat or brewer’s yeast.104 A 6-year follow-up study at the same center found that 26/37 (70%) patients reported improvement in HS symptoms with a brewer’s and baker’s yeast-free diet and operative intervention. Similarly, 32/37 (82%) patients experienced symptom recurrence after reintroducing restricted foods. 10% of these patients completed serological testing by measuring immunoglobulin G (IgG) antibodies, which identified yeast intolerance in 20%, wheat intolerance in 29%, and cow’s milk intolerance in 23%.105 Both studies, with small sample sizes and lacking control groups, were confounded by the inclusion of surgical excisions performed on all patients. Moreover, it remains unclear whether a similar diet would benefit patients without comparable dietary intolerances.
Zinc supplementation has been associated with improved HS symptoms. A 2018 case control study highlighted a higher prevalence of low serum zinc levels among HS patients compared to controls. Moreover, low zinc levels were found to be correlated with more severe Hurley staging, increased DLQI scores, and heightened symptom severity.106 In cases where traditional treatments like systemic antibiotics, isotretinoin, surgery, or antiandrogens proved ineffective, Brocard et al revealed that administering 90 mg of zinc gluconate daily resulted in complete remission for 8/22 (36%) and partial remission for 14/22 (63.6%) patients.107 Similarly, Molinelli et al and Hessam et al found that zinc supplementation was associated with significant reductions in acute flares, disease severity, and longer disease-free survival.108,109
HS patients exhibit a higher prevalence of vitamin D deficiency compared with controls,110,111 and vitamin D serum levels are inversely correlated with HS disease severity.112 In HS patients with low vitamin D, Guillet et al revealed that vitamin D supplementation significantly decreased the number of nodules at 6-month follow up, noting a correlation between response to HS therapies and an increased vitamin D levels following supplementation.113 (See Table 3)
79
IV
Cross-sectional study with 221 patients with HS, explored potential association between adherence to a Mediterranean diet, physical activity and HS severity
Disease severity, Hurley, and IHS4 (International Hidradenitis Suppurativa Severity Score System)
Higher adherence to a Mediterranean diet was associated with lower disease activity, lower self-reported Hurley and lower IHS4 (International Hidradenitis Suppurativa Severity Score System)
The MD could be an appropriate dietary pattern for patients with HS due to its anti-inflammatory properties, and combining this with increased levels of physical activity could have additional benefits
80
IV
Case-control with 35 patients with HS, 35 healthy subjects, evaluated several anthropometric measures, lifestyle (Mediterranean diet adherence, and physical activity level) and the perceived physical and mental health status were evaluated
35 patients with HS, 35 healthy subjects
Disease severity (via Hurley stage system or Sartorius score)
HS patients showed a significantly lower adherence to the Mediterranean diet than that of controls. Hidradenitis patients showed significantly higher values of body mass index, waist circumference, body composition, fat mass, and lower values of physical and mental health status compared to controls, while both groups showed a similar moderate physical activity level which can be assumed to counteract the negative effects of obesity or poor nutritional pattern in hidradenitis patients. However, none of the evaluated variables were correlated with the severity of the disease, assessed by means of the Hurley stage system or the Sartorius score. Instead, the Sartorius score showed a positive correlation with the duration of hidradenitis, mainly imputable to the diagnostic delay and the consequent long lasting inflammatory status
Although nutritional factors and lifestyle can be important and modifiable factors in the hidradenitis suppurativa course, the detrimental effect of chronic inflammation and delayed management are clearly prevalent and heavily influence the disease burden
88
IV
Studied 12 patients who underwent surgical excision or localized treatments followed by diet modification (controlled brewer's yeast-free diet for 12 months)
Clinical symptoms, skin lesion regression or recurrence
Diet demonstrated stabilization of clinical symptoms; skin lesions regressed over the 12-month treatment period. Similarly, all the patients demonstrated an immediate recurrence of skin lesions following accidental or voluntary consumption of beer or other foods containing brewer’s yeast or wheat
Surgery followed by the elimination of the foods containing or made with the yeast resulted in a rapid stabilization of the dermatologic manifestation and a slow, but complete, regression of the skin lesions within a year
89
IV
185 patients with a self-evaluative questionnaire; 37 treated following a protocol (yeast-exclusion diet followed by operative intervention) and 148 were members of a support group for patients with HS treated by other centers
Yeast-exclusion diet followed by operative intervention compared with members of a support group for patients with HS
HS symptomatology
In the diet group, 70% had an improvement of HS symptomatology. 87% of patients demonstrated an immediate recurrence of skin lesions less than a week after consuming a food containing the yeast
Stabilization and regression of hidradenitis suppurativa with protocol diet, presumably by decreasing the local and systemic inflammation, leading to a less invasive operative treatment. These new findings seem to link hidradenitis suppurativa to food intolerance and gut dysbiosis
90
IV
Multicenter, prospective clinical and analytical case–control study with 122 patients with HS and 122 control subjects was designed to assess the possible association between HS and serum zinc levels
122 patients with HS compared to 122 control subjects
Disease severity, Dermatology Life Quality Index, affected sites
Low serum zinc levels were associated with Hurley III, Dermatology Life Quality Index ≥ 9, number of affected sites ≥ 3, genital location, and perineal location
Low serum zinc levels are more prevalent in HS than in a healthy population, an indicator that may also be associated with disease severity
91
IV
22 patients treated with 90 mg of zinc gluconate per day
Clinical response
There was a clinical response with zinc gluconate in all patients, with 8 complete remissions (CR) and 14 partial remissions (PR)
Zinc salts could provide a new therapeutic alternative for the treatment of hidradenitis suppurativa
92
IV
92 patients with Hurley stage I and III HS were evaluated, divided into 2 groups according to treatment received or not received. 47 patients started oral therapy with capsules containing 90 mg of zinc gluconate and 30 mg of nicotinamide once daily for 90 days, compared to a control group of 45 patients who did not receive any treatment
47 patients treated with oral zinc gluconate and nicotinamide compared to a control group of 45 patients who did not receive any treatment
Number and duration of acute flares, VAS, Dermatology Life Quality Index, International HS Severity Score System
There was a significant reduction in the number and mean duration of acute flares in the treated versus control groups. Patients of the treated group correspondingly reported a marked reduction in mean Visual Analogue Scale, Dermatology Life Quality Index, and International HS Severity Score System scores compared with the control group at 12 and 24 weeks. Disease-free survival was significantly longer in the treated group, and it showed sustained improvement even after discontinuation of oral supplementation. Slightly decreased or stable International HS Severity Score System score and pain Visual Analogue Score during the maintenance treatment was collaterally observed in the treated group with no statistically significant difference at 24 weeks
Zinc and nicotinamide supplementation in patients who have previously been treated with tetracyclines (minocycline) may be a valuable and a well-tolerated maintenance approach for mild to moderate HS, extending the disease-free survival reducing the rate and duration of flares
93
IV
To evaluate the efficacy of anti-inflammatory oral zinc gluconate, 90 mg/day, combined with
Modified HS score and Dermatology Life Quality Index, Number of inflammatory lesions, fistulas, visual analogue scale
After 3 months of combination therapy,
The combination therapy of zinc gluconate and topical triclosan can be considered as an anti-inflammatory treatment for HS patients in Hurley stage I and initial Hurley stage II
97
IV
14 patients supplemented with vitamin D evaluated for number of nodules and frequency of flare-ups at 6 months
Number of nodules and frequency of flare-ups
Supplementation significantly decreased the number of nodules at 6 months and the endpoints (20% decrease in number of nodules and frequency of flare-ups) were achieved in 79% of patients
Disease is associated with a major vitamin D deficiency, correlated with the disease severity. It suggests that vitamin D could significantly improve the inflammatory nodules, probably by stimulating the skin innate immunity
Psoriasis is a chronic inflammatory skin disorder with numerous subtypes,114 most commonly plaque psoriasis which is characterized by well-demarcated erythematous plaques with silvery scaling on extensor surfaces, trunk, and the scalp. Psoriasis appears with a similar frequency in both men and women with a mean onset age of 33 years, although studies indicate that it may present earlier in women.115 As there is no known cure for psoriasis and given the complex nature with a multifaceted origin that is influenced by both genetic and environmental factors,114 dietary intervention may be a potential therapeutic option to explore to alleviate symptoms.116
The gut and skin immune systems are interconnected. Research has shown an increased prevalence of intestinal inflammation in individuals with psoriatic arthritis, with gut inflammatory lesions occurring in 16% of psoriasis patients which were identified via ileocolonoscopy.117,118 Although the exact underlying mechanisms remain unclear, there is a mutual relationship between psoriasis and inflammatory bowel diseases, including Crohn’s disease (CD). People with CD are five times more likely to develop psoriasis compared to those without CD, and individuals with psoriasis have an elevated risk of developing CD.119
Studies on the gut microbiome consistently report imbalances in individuals with psoriasis, although the specific compositions of intestinal microbiota may vary among psoriasis patients.120,121 The gut microbiota are known to play a vital role in maintaining host equilibrium and regulating inflammation in the gut and skin, particularly in the context of Th17, a cytokine associated with CD.122 Th17 cells govern the IL-17A and IL-17F production, which modulates gut inflammation.123
A randomized controlled trial (RCTs) demonstrated that dietary interventions can have specific effects on gut microbiota diversity and inflammatory markers. For example, the consumption of fermented foods has been found to reduce IL-6, a mediator of chronic inflammation that is elevated in chronic inflammatory diseases such as rheumatoid arthritis and type 2 diabetes.124,125 Notably, elevated IL-6 expression has been linked to psoriatic skin lesions and increased keratinocyte proliferation.126,127
Psoriasis can profoundly impact quality of life. and many patients seek information regarding lifestyle changes that may help with disease management. Studies indicate that individuals suffering from psoriasis display strong motivation to modify their diets, as they view these interventions as natural, safe, and self-empowering.128,129 While there are numerous dietary suggestions for psoriasis in popular literature, the scientific literature, particularly randomized controlled trials (RCTs), is notably lacking. There is a dearth of studies examining the impacts of widely recommended dietary approaches, such as the Paleolithic or vegetarian diets. This limited body of research on the relationship between diet and psoriasis highlights a significant knowledge gap, making it challenging for both patients and clinicians to engage in informed discussions on this subject.128 Below are the top dietary interventions and supplements reported in literature.
The association between obesity and psoriasis is well-documented. Studies have found a correlation between elevated levels of obesity-related adipokines, such as leptin, and a higher risk of developing psoriasis. Moreover, individuals with psoriasis are more likely to be obese compared to those without the condition,130 and a higher body mass index (BMI) is associated with more severe psoriasis symptoms.131,132 Importantly, obesity has been found to diminish the effectiveness of psoriasis treatments by as much as 50%.133 These associations may be due to increased adiposity leading to heightened inflammation from overproduction of proinflammatory cytokines such as TNF-α, IL-1, IL-6, and IL-8.134
Numerous RCTs have indicated that weight loss through hypocaloric diets is beneficial for individuals with psoriasis who are classified as overweight or obese, which is defined as BMI ≥ 25.0. When caloric restriction is implemented in conjunction with pharmacologic therapies, these diets lead to significant improvements in dermatology life quality index (DLQI),135,136 psoriasis area and severity index (PASI),136–138 body surface area (BSA),138 and weight loss compared to controls. Serum markers such as triglycerides,135,139 total cholesterol,135 plasma glucose, and glycated hemoglobin also significantly decrease.140 Jensen et al showed that the positive effects on PASI and BSA can last for one year.140
Dietary weight loss has been demonstrated to be beneficial in conjunction with multiple systemic treatments, including biologic therapies,138 cyclosporine,141 methotrexate,137 and psoralen ultraviolet A therapy (PUVA). This is particularly important for individuals who have both obesity and psoriasis, as they face an elevated risk of experiencing adverse effects from systemic medications. Weight reduction not only enhances the treatment effectiveness but also reduces the likelihood of drug toxicity.142
However, weight reduction alone may not be sufficient to maintain psoriasis remission. In one RCT, patients in remission for 12+ weeks on methotrexate therapy were randomly assigned to receive a hypocaloric diet or free diet after discontinuing their methotrexate. The outcome of this study revealed no significant difference between these two groups in terms of maintaining psoriasis remission.143
Gluten-free diets have gained popularity in recent decades, and evidence suggests that this may benefit some psoriasis patients. Celiac disease (CD) and psoriasis are hypothesized to have a bidirectional relationship, where people with psoriasis have a higher odd of CD and vice versa.144,145 Psoriasis patients were observed to have elevated levels of IgA antigliadin antibodies (AGA), which are frequently utilized in diagnosing celiac disease, and increased antibody levels are linked to more severe psoriasis.146
Studies indicate that gluten-free diets may be helpful for patients with CD or serologic markers of gluten sensitivity. Adopting a gluten-free diet not only leads to a reduction in the severity of psoriasis but also alleviates gastrointestinal symptoms.147 In psoriasis patients with AGA antibodies, a 3-month adherence to a gluten-free diet resulted in significant improvements in PASI scores, and symptoms rebounded to pre-diet scores in 60% of patients after resuming a normal diet.148 Kolchak et al demonstrated that individuals with higher AGA antibodies experienced more substantial reductions in their PASI scores when they maintained a gluten-free diet for one year.149
Psoriasis patients without serological markers for gluten sensitivity serum markers do not benefit from gluten-free diets.148
The Mediterranean diet (MedD) promotes the consumption of healthy fats and plant-based foods, proving beneficial for weight reduction.150 While there is no conclusive evidence establishing a causal link between MedD and psoriasis severity, numerous observational studies suggest a connection between poor adherence to MedD and increased PsO severity.151 Korovesi et al revealed that MedD adherence is inversely associated with psoriasis risk, severity, and quality of life,152 and Barrea et al’s case control study revealed that higher percentages of psoriatic patients had lower PREDIMED scores compared to control groups.153 Similarly, the 2018 NutriNet-Santé Cohort study showed an inverse relationship between MEDI-LITE score and severe psoriasis.
Furthermore, psoriatic arthritis has been inversely linked to MedD adherence. A 2020 multicenter cross-sectional study found a negative association between DAPSA and MedD adherence154; Molina-Leyva et al reported that the proportion of patients with PsA was lower in people with greater adherence to MedD.151 Randomized clinical trials are needed to establish the role of MedD in psoriasis.
In the era of biologics, there is an increasing prevalence of complementary and alternative medicine (CAM) use among psoriatic patients,155 and CAM use is high compared to controls.156 Common dietary supplements include fish oils, vitamin D, vitamin B12, and selenium.157
Although many patients believe that fish oil is helpful to improve their skin health,128 the results from double-blinded RCT are mixed.158–167 Many of the RCTs were conducted in the 1980s-1990s and utilized less objective measures or controls. Meta-analyses of RCTs yield similarly controversial findings.168–170 Additional well-controlled and randomized studies are needed to confirm the relationship between fish oil and psoriasis.
Vitamin D is a popular supplement among patients.128 There is an increased prevalence of vitamin D deficiency in psoriatic patients compared to the general population,171 and vitamin D deficiency has been correlated with worse psoriasis severity.172 Topical vitamin D is a well-established component of psoriasis treatment, but the benefit of oral vitamin D is unclear.173 RCT results are mixed, but open-label trials have shown beneficial results.174–177 A 2021 meta-analysis reports a lack of significant evidence for oral vitamin D supplementation and concludes that additional RCTs with larger sample sizes are needed to yield more conclusive data.178
Vitamin B12 deficiency has been reported in psoriasis patients.179,180 However, limited studies have investigated the efficacy of intramuscular B12 injections in psoriasis treatment. A 2001 intra-individual trial suggested that B12 and avocado oil may be beneficial for long-term therapy.181 In contrast, Baker and Comaish’s double-blinded RCT revealed no statistically significant benefit of vitamin B12 injections compared to placebo.182
Selenium has been found to prevent ROS damage, reduce cell proliferation, and catalyze apoptosis in keratinocytes.183 Decreased selenium levels have been reported in psoriatic patients,184–186 and selenium supplementation appears to yield varying results in patients with different psoriasis subtypes. Kharaeva et al’s double-blinded RCT reported that coenzyme Q(10) 50 mg/d, vitamin E 50 mg/d, and selenium 48 mug/d dissolved in soy lecithin for 30-35 days resulted in significantly decreased psoriasis severity compared to soy lecithin controls.187 However, selenium did not demonstrate benefit in plaque psoriasis management when used as monotherapy or adjuvant therapy with 5% salicylic acid ointment or phototherapy.184,187–189 (See Table 4).
117
I
Systematic review and meta-analysis of 6 RCTs
N/A
Weight loss interventions, PsO/PsA in obese patients
Weight loss following lifestyle interventions improves psoriasis compared with controls (p < 0.001). 3 studies on pharmacologic interventions yielded conflicting results. 2 cohort studies suggested that gastric bypass reduces the risk of developing psoriasis (p < 0.01)
Weight loss can improve pre-existing PsO and PsA, as well as prevent the development of PsO in individuals with obesity
119
II
RCT of 44 obese patients with plaque PsO
Energy-restricted diet (20 kcal/kg/ideal body weight/day) with n-3 PUFAS (2.6 g/day) or usual diet. All patients continued their immuno-modulating therapy throughout the duration of the RCT
PASI, DLQI, body weight, WC, laboratory results (serum triglycerides, serum total cholesterol, n-6/n-3 ratio)
Data was measured at baseline, 3 months, and 6 months. PASI, itch scores, and DLQI decreased significantly compared with baseline (p < 0.05). Among patients with an energy-restricted diet, a significant decrease in body weight, waist circumference, serum triglycerides, serum total cholesterol, and n-6/n-3 ratio intake occurred (p < 0.05). No significant changes were observed among controls.
In PsO patients with obesity, an energy-restricted diet with immuno-modulating therapy improved clinical outcomes and improved metabolic profiles
120
II
RCT of 60 overweight/obese patients with psoriasis
Intervention group completed energy-restricted diet (800-1000 kcal/day) for 8 weeks, followed by 8 weeks of 1200 kcal/day. Control group continued ordinary healthy foods
PASI, DLQI
At week 16, mean weight loss was greater in intervention group compared with controls (p < 0.001). Mean differences in PASI (p = 0.06) and DLQR (0.02) were greater in energy-restricted diet group compared with controls
In PsO patients who are overweight, an energy-restricted diet improved PASI scores and reduced DLQI.
121
II
RCT of 303 overweight/obese patients with plaque psoriasis who did not achieve clearance after 4 weeks of systemic therapy
20-week dietary plan + physical exercise for weight loss, or simple counseling about utility of weight loss for controlling psoriatic disease
PASI
Mean PASI reduction was greater in dietary intervention arm than information-only arm (p = 0.02), and PASI scores reduction ≥ 50% was more frequent in the intervention group (p = 0.006). Weight-loss target (≥ 5% from baseline) was achieved more frequently in the dietary intervention arm (p = 0.001).
In systemically treated PsO patients who are overweight/obese, a 20-week dietetic intervention with increased physical exercise reduced PsO severity
122
II
RCT of 262 overweight/obese patients with psoriasis on biologic therapy
Low-calorie (≤ 1000 kcal/day) or normal diet for 24 weeks
PASI
Mean weight loss and PASI score improvement was greater in dietary intervention arm than controls. PASI 75 was achieved more frequently in the diet group (p < 0.001), and mean BSA was lower in the diet group compared with controls
Weight reduction in obese PsO patients on biologic therapy may increase drug efficacy
123
II
RCT of 60 men with class I obesity, chronic plaque psoriasis, and non-alcoholic fatty liver disease
Low calorie diet + exercise + immunosuppressive drugs or immunosuppressive drugs only for 12 weeks
PASI, weight, BMI, WC, laboratory results (triglycerides, liver enzymes), DLQI
Low calorie diet group had significant improvement in all measured variables, including: BMI, waist circumference, AST, ALT, triglycerides, PASI, and DLQI). No significant improvements were achieved in control group
For male patients with chronic plaque psoriasis and non-alcoholic fatty liver disease, dietary interventions control BMI, increase psoriasis responsiveness to immunosuppressive therapy, improves quality of life, controls hepatic enzymes, and reduces triglycerides.
124
II
RCT of 32 patients with psoriasis
Two phases: low-energy diet or control phase for 16 weeks, followed by weight maintenance for 48 weeks
PASI, DLQI
PASI, DLQI, and weight were reduced after the 16-week low energy diet period. At week 64, there was an average regain in weight compared with week 16, but PASI and DLQI were maintained
Long-term weight loss in patients with psoriasis reduced psoriasis severity
125
II
RCT of 61 obese patients with chronic plaque psoriasis
Cyclosporine + low-calorie diet or cyclosporine alone) for 24 weeks
PASI
At week 24, the mean body weight reduction and PASI 75 response was greater in the intervention group compared with controls (p < 0.001). More patients from the control group withdrew from the study compared with the intervention group (p < 0.001)
For obese patients with moderate-to-severe psoriasis, response to low-dose cyclosporine was increased if low-calorie diet is included in the treatment regimen
127
II
Questionnaire to 200 patients with moderate-to-severe chronic plaque psoriasis about perception of diet on psoriasis severity. RCT of 42 obese patients with PASI 75 ≥ 12 weeks after methotrexate therapy
Hypocaloric diet or free diet for 24 weeks, with subsequent follow-up for 12 weeks
Questionnaire, body weight, PASI
Most patients believed that a dietary modification can influence psoriasis. Obese patients in psoriasis remission had significant body weight reduction after 12 weeks, which was maintained at 24 weeks. No significant differences in maintenance of psoriasis remission were observed
Weight reduction only may be insufficient for maintaining remission for moderate-to-severe psoriasis in obese patients
131
IV
Multicenter cross-sectional study of 218 PsO patients and 264 controls
N/A
Celiac screening; positive celiac serology prompted histologic evaluation
More PsO patients had positive anti-tissue transglutaminase antibodies compared with controls (p < 0.05). CD diagnosis was confirmed histologically in all patients with positive antibodies. A 6-month GFD was associated with significantly improved skin lesions in the patients with celiac and psoriasis
There is a high prevalence of CD in psoriasis, and GFD can improve skin lesions in CD and psoriasis
132
III
Cohort study of 33 AGA-positive and 6 AGA-negative PsO patients
3-month GFD + 3 months of ordinary diet
PASI, duodenal biopsy histology
AGA-positive PsO patients had significantly decreased mean PASI following GFD, whereas AGA-negative patients did not improve. When ordinary diet resumed, PsO symptoms resumed in 18/30 patients with AGA who had completed the GFD
AGA-positive PsO patients may improve on a GFD
133
III
Cohort study of 97 PsO patients + 91 healthy controls
Strict GFD for 2 years
Gliadin IgA antibodies, PASI
Patients who had high gliadin IgA antibodies were placed on a GFD without change to ongoing psoriasis treatment. Psoriasis lesions improved in all patients, with the most significant decline in PASI and reduction in pharmacologic treatment in patients with strongly positive gliadin IgA
AGA positivity is significant among psoriatic patients who are not diagnosed with celiac disease or gluten sensitivity, and AGA testing can identify patients who may benefit from GFD
135
IV
Cross-sectional study of 89 psoriasis patients
N/A
PREDIMED compared with severity of psoriasis, cardiovascular profile, and CRP
Higher adherence to MedD is asssociated with reduced psoriasis severity. Higher frequency of hypertension, diabetes, and large waist were observed in patients with greater adherence to MedD
Mediterranean diet should be implemented for PsO patients as part of their ongoing treatment
136
IV
Cross-sectional study of 69 mild-to-severe psoriasis and 69 healthy matched controls
N/A
Med Diet Score, PASI, and DLQI
MedD diet was inversely associated with risk of psoriasis, PASI, and DLQI. PASI was inversely correlated with fish, extra virgin olive oil, and legumes while positively correlated with dairy products
There is an inverse association between MeD dietary adherence and psoriasis severity, occurance, and quality of life
137
IV
Cross-sectional case-control study of 62 mild-to-severe PsO patients and 62 matched controls
N/A
PREDIMED compared with PASI, CRP, and bioelectrical impedance analysis for body composition
More psoriatic patients had lower PREDIMED scores compared to controls. PASI score was positively associated with fat mass percentage and CRP, and PASI and CRP were associated with PREDIMED scores. Extra virgin olive oil and fish consumption had inverse relationship with PASI and CRP levels
There is an inverse association between MeD dietary adherence and psoriasis severity. Psoriatic patients had significant differences in body composition compared with BMI-matched controls, and MedD dietary interventions may be a safe adjuvant treatment
138
IV
Cross-sectional study of 211 PsA patients
N/A
DAPSA, CPDAI, BMI, and PREDIMED
DAPSA was negatively correlated with Mediterranean diet adherence and positively associated with BMI
Since higher disease activity (DAPSA) is correlated with MedD dietary adherence, the MedD diet may have a potential anti-inflammatory benefit
142
II
RCT of 20 hospitalized acute guttate PsO patients
Daily infusions with n-3 FA lipid emulsion (100 mL/day of 2.1 g eicosapentanenoic [EPA] and 21 g docosahexaenoic acid [DPA]) or n-6 lipid emusion (EPA + DHA < 0.1 g/100 mL)
Clinical disease characteristics, leukotrienes, and platelet-activating factors
Disease severity significantly improved in all patients of the n-3 group (p < 0.05), whereas moderate improvement was observed in the n-6 group. A ten-fold increase in 5-lipoxygenase products was observed in the n-3 group but not the n-6 group, whereas platelet activating factor generation decreased in the n-3 group but increased in the n-6 group
IV n-3 FA supplementation can modulate eicosanoid metabolism and appears to rapidly benefit inflammatory skin lesions in acute guttate psoriasis
143
II
RCT of 83 hospitalized chronic plaque-type PsO patients
Daily infusions of n-3 FA lipid emulsion (omegavenous; 200 mL/day with 4.2 g of EPA and DHA)) or n-6 lipid emulsion (lipovenous; EPA + DHA < 0.1 gm/100 mL) for 14 days
Changes in PASI and self-assessments by patient
PASI score reduced more in the u-3 group than u-6 group (p < 0.05), as well as severity of psoriasis, reduction in erythema, and scaling. Response was observed more frequently in u-3 than u-6 group. An increase in EPA concentration, leukotriene B5, and thromboxane B3 generation occurred in the u-3 group but not then u-6 group
IV n-3 FA supplementation can effectively treat chronic plaque-type psoriasis
144
II
RCT of 18 plaque PsO patients
Fish oil or placebo olive oil capsules for 15 weeks, with UVB in weeks 3-11 for both groups
BSA, scaling, erythema, thickness
After phototherapy and 4 weeks later, the fish oil group had a greater decrease in total BSA and greater improvement compared with patients in the olive oil group
Given its safety and health-promoting features, fish oil could serve as an ideal adjunctive therapy for psoriasis treatment
145
II
RCT of 28 PsO patients
10 fish oil or placebo olive oil capsules daily for 8 weeks
BSA, scaling, erythema, pruritus
In the fish oil group, there were significant reductions in itching, erythema, and scaling. No significant change was observed in the placebo group
Fish oil may serve as a treatment for psoriasis
146
II
RCT of 145 PsO patients
3 g n-3 PUFA/day or 3 g olive oil/day for 24 weeks
Disease activity, analgesic use, leukotriene formation
Compared with controls, the n-3 PUFA group had non-significant reductions Disease Activity Score (DAS28-CRP), 68 tender joint count, enthesitis score, and PASI. There was significantly reduced NSAID and paracetamol usage compared with controls, and the n-3 PUFA group had reduced formation of leukotriene B4 and higher formation of leukotriene B5 compared with controls
The n-3 PUFA group showed improvement in outcome measures for disease activity, although not statistically significant
147
II
RCT of 38 PsA patients
12 Efamol Marine (evening primrose oil + fish oil) or placebo capsules daily for 9 months, followed by placebo capsules for 3 months. At month 3, patients were instructed to reduce NSAID intake
Skin disease activity (BSA, severity, pruritus), NSAID usage, arthritis disease activity (morning stiffness duration, Ritchie articular index, number of active joints, ESR, CRP)
Skin disease activity measures were unchanged by the Efamol Marine, and NSAID requirements remained the same for both treatment and control groups. No changes were observed in arthritis activity. In the treatment group, a decrease in leukotriene B4 was observed in the active phase, followed by a rise in serum leukotriene B4 and TXB2 during the placebo phase
Efamol Marine may modify prostaglandin metabolism in PsA patients, although it did not provide clinical benefit or reductions in NSAIDs. A larger dose of essential FA may be required
148
II
RCT of 145 moderate-to-severe PsO patients
6 g fish oil/day with 5 g of eicosapentaenoic and docosahexaenoic acid or corn oil with mostly n-6 FA. All patients were instructed to reduce saturated FA intake
PASI; patient's subjective assessment of erythema, iscaling, pruritus, and effect on daily living; selected 10-cm2 area representing moderate-to-severe psoriasis evaluated for erythema, scaling, and cellular infiltration
In the fish oil group, serum phospholipids had an increase in n-3 FA, decrease in arachidonic acid to eicosapentaenoic acid, and decrease in n-6 FA. PASI did not significantly change in both groups, although scaling was reduced in both. For the fish oil group, there was no correlation between clinical improvement and increased serum n-3 FA. For the corn oil group, there was a correlation between clinical improvement and increase in eicosapentaenoic acid and total n-3 FA
There was no significant difference between n-3 FA and corn oil supplementation in PsO treatment. Increase in serum n-3 FA was not correlated with clinical improvement
149
II
RCT of 25 plaque PsO patients
10 fish or olive oil capsules 3x daily for the whole study, in addition to betamethasone diproprioinate to their psoriatic plaques for the first 3 weeks. Study was completed after 9 weeks of capsules, or when global severity score had worsened to pre-treatment level
Total BSA, scaling, erythema, thickness
Most patients worsened after discontinuing steroids. There was no significant difference found between fish and olive oil groups through survival analysis
Fish oil is minimally effective as a monotherapy when used in high doses with dietary control
150
II
RCT of 145 plaque PsO patients
10 g fish oil daily with 1.8 g eicosapentaenoic acid or isoenergetic amount of olive oil for 8 weeks
PASI; patient's subjective assessment of erythema, scaling, pruritus, and effect on daily living; selected 10-cm2 area representing moderate-to-severe psoriasis evaluated for erythema, scaling, and cellular infiltration
There were no significant differences in clinical manifestations in either group. For the fish oil group, the amount of n-3 FA in serum phospholipids was significantly increased at the end of the trial
Increased n-3 FA was not correlated with clinical improvement in plaque psoriasis
151
II
RCT of 43 PsA patients
Seal or soy oil for 2 weeks. Patients continued NSAIDs and DMARDs during the study period
Joint pain intensity, patient's global assessment of disease, PASI, laboratory assessments
The seal oil group had a significant improvement in patient's global disease assessment 4 weeks post-treatment. Both groups had improved tender joint counts but the differences between groups was not significant. The n-6 : n-3 FA ratio, arachidonic acid, and eicosapentaenoic acid reduced after seal oil
Seal oil treatment was followed by improved global assessment of disease. Serum FA composition shifted towards an anti-inflammatory profile
152
I
Systematic review and meta-analysis of 10 u-3 PUFA RCTs
PASI, erythema, scaling, pruritus
u-3 FA had a significant reduction in PASI score, erythema, scaling and correlated with higher dosage of u-3 supplementation. Changes in itching and percentage of total body surface area were not significant
Current evidence indicates that u-3 PUFA supplementation can improve PASI, erythema, and scaling for psoriasis patients
153
I
Systematic review and meta-analysis of 13 u-3 PUFA RCTs
PASI
3 RCTs had usable data for meta-analysis. Fish oil supplementation did not significantly reduce PUFA
Current evidence indicates that fish oil supplements are not beneficial for psoriasis
154
I
Systematic review and meta-analysis of 18 u-3 PUFA RCTs
PASI, lesion, pruritus
Fish oil monotherapy did not significantly change PASI, pruritus, or lesion area. Fish oil/u-3 PUFAS in combination with conventional treatments resulted in reduced PASI and lesion area. Fish oil reduced risk factors for metabolic disease, cardiovascular disease, and obesity while regulating inflammatory mediators
Current evidence indicates that fish oil may have benefits on psoriasis and its comorbidities when combined with conventional treatments
158
III
Open-label study of 40 PsO patients
3 groups: 1 alpha, hydroxyvitamin D3 orally 1.0 μgs/day for 6 months; 1 alpha,25-dihydroxyvitamin D3 orally 0.5 μg/day for 6 months; or 1 alpha,25-dihydroxyvitamin D3 topically 0.5 μg/g for 8 weeks
Improvement was observed in all groups. The most rapid response was observed in Group 3, with improvement noted in 84% patients when applied for 3.3 ± 1.2 weeks. No side effects were observed in any groups
Active vitamin D3 metabolites may treat psoriasis lesions. Psoriasis pathogenesis may involve abnormalities in vitamin D metabolism or response
159
III
Non-randomized trial of 25 patients with psoriasis or vitiligo
Both patient groups (psoriasis and vitiligo) received 35,000 IU vitamin D3 daily with low-calcium diet for 6 months
PASI, repigmentation, laboratory assessments
Though all patients presented with low baseline 25(OH)D3, 25(OH)D3 levels increased significantly after 6 months of treatment. PTH levels significantly decreased in both groups. PASI score improved significantly in all 9 patients with psoriasis, and 14/16 vitiligo patients experienced 25-75% repigmentation
High-dose vitamin D3 may be an effective therapy for psoriasis and vitiligo
160
II
RCT of 65 PsO patients
23 vitamin D3 100,000 IU monthly or placebo for 12 months
PASI, Physicians Global Assessment (PGA), DLQI, and PsO Disability Index (PDI)
There were no significant differences between the intervention and control for all outcome measures
Vitamin D3 supplementation at 100,000 IU/month is not an effective treatment for psoriasis
161
II
RCT of 41 PsO patients
Vitamin D3 1 μg/day or placebo
Improvement was observed in both intervention (45% patients) and control (38%) patients
Vitamin D3 supplementation at 1 μg/day is not an effective treatment for psoriasis
162
I
Systematic review and meta-analysis of 7 RCTs (4 qualitative analysis, 3 quantitative analysis)
PASI
Vitamin D supplementation for 6 months was effective for reducing PASI. However, results became non-significant after the Hartung-Knapp adjustment
Vitamin D supplementation could not be verified as a treatment for psoriasis
165
II
RCT of 13 chronic plaque PsO patients
Vitamin D3 analog calcipotriol or vitamin B12 cream with avocado oil in intraindividual R/L-comparison for 12 weeks
PASI score, subjective evaluation of patient & investigator, and 20-MHz sonography
Both PASI and 20-MHz showed no significant differences between treatments. Effects of calcipotriol peaked within first 4 weeks and subsided. Effects of B12 cream with avocado oil remained at constant level throughout observation period, and patients & investigators assessed B12 cream with avocado oil as significantly better tolerated than calcipotriol
Vitamin B12 cream with avocado oil has potential as a long-term and well-tolerated topic therapy for psoriasis
168
II
RCT of 69 PsO patients
600 μgs of selenium-enriched yeast, 600 μgs of selenium-enriched yeast + 600 IU vitamin E, or placebo for 12 weeks
Laboratory evaluations (selenium concentrations in whole blood and plasma, red cell glutathione peroxidase activity, plasma vitamin E), skin selenium concentration, psoriasis severity
At baseline, psoriasis patients' mean concentrations of selenium were reduced compared to matched healthy controls, but red cell glutathione peroxidase (GSH-Px) activity was normal. After 12 weeks, the patients' mean whole blood, plasma, and platelet selenium concentrations, platelet GSH-Px activity, and plasma vitamin E levels increased significantly. However, mean skin selenium concentration and red cell GSH-Px activity were unchanged. Neither supplementation group reduced the severity of psoriasis
Psoriasis lesions may not experience any improvement with selenium-enriched yeast, with or without vitamin E. This absence of improvement may be attributed to the lack of increased selenium content in the skin despite supplementation
171
II
RCT of 58 PsO patients
Groups EP1 and PsA1 received coenzyme Q, vitamin E, selenium with soy lecithin for 30-35 days. Groups EP2 and PsA2 (placebo) received soy lecithin
Oxidative stress markers, PASI, Severity Score (SS)
At baseline, patients had increased superoxide release from granulocytes, increased copper/zinc-superoxide dismutase and catalase activity in granulocytes in EP patients and decreased in PsA patients, decreased copper/zinc-superoxide dismutase activity, and altered catalase activity in the psoriatic epidermis. Dietary supplementation resulted in improvement of clinical conditions and faster normalization of oxidative stress markers compared with controls
Antioxidant supplementation with coenzyme Q, selenium, and vitamin E may be useful for managing severe psoriasis
172
II
RCT of 37 PsO patients and 20 healthy controls
Narrowband UVB 5x weekly and 200 mug selenium daily or placebo for 4 weeks
PASI, selenium, sTNF-R1, and CRP
Baseline sTNF-R1 was correlated to PASI (p < 0.05). Treatment resulted in nearly parallel decreases in PASI in both groups
In active psoriasis patients, levels of sTNF-R1 and CRP and increased. Selenomethionine supplementation for 4 weeks is ineffective for psoriasis
173
II
RCT of 22 inpatient plaque PsO patients and 10 healthy controls
Topical 5% salicylic acid ointment, 0.1-0.3% dithranol ointment, and 200 μgs daily of selenomethionine or placebo for 4 weeks
PASI, selenium, sTNF-R1
There was a positive correlation between PASI and sTNF-R1. Nearly complete remission of skin lesions was achieved in both psoriasis groups after 4 weeks, but PASI score was higher in the intervention group (p < 0.05). Correlation between PASI score and TNF-R1 reversed
Increased sTNF-R1 may indicate active psoriasis. Selenomethionine supplementation was ineffective for plaque psoriasis and may contribute to high TNF-R1 despite skin lesion remission
Atopic dermatitis (AD), commonly referred to as eczema, is a persistent and recurring inflammatory skin condition that constitutes part of the “atopic triad” (atopic dermatitis, asthma, and allergies). Globally, it is estimated that AD impacts approximately 3.4-33.7% of the population, with a higher prevalence among women.190 The increasing prevalence over the past decades suggests a potential connection to environmental factors triggering the condition in predisposed individuals.191–194 Diet is proposed as a significant factor in triggering AD, alongside other environmental exposures like pollution, UV radiation, and climate.193,195 In addition, diet modifications have been proposed as strategies to ameliorate flares or prevent disease. Here, we examine the existing literature regarding the impact of diet on AD.
AD pathogenesis is associated with a dysfunctional skin barrier. Loss-of-function mutations in the FLG gene result in impaired filaggrin, a crucial protein that links keratin filaments and interacts with lamellar bodies, consequently compromising the skin barrier function.196 Filaggrin-poor skin is believed to facilitate greater allergen penetration, thereby heightening allergen sensitivity.197 Various case-control studies have indicated that mutations in filaggrin are linked to an elevated risk of developing egg or peanut allergies.198,199 Eczematous skin lesions additionally display increased dendritic cells, which express high-affinity receptors for IgE that facilitate allergen uptake. Increased receptor expression has been associated with greater lesion severity.196
Similar to the skin, the intestinal epithelium is integral to the innate immune system, safeguarding the body against environmental threats. The gastrointestinal tract can share analogous “leaky” characteristics with skin epithelium, characterized by heightened permeability and reduced protection.200 A compromised gut barrier is believed to permit the increased passage of antigens from ingested contents and lead to an inflammatory response.201 Elevated intestinal permeability has been linked to more severe cases of atopic dermatitis (AD).202,203
Microbiota alterations have been associated with AD. Skin dysbiosis is mediated through increased concentrations of
In recent decades, there have been ongoing discussions revolving around the influence of food triggers and elimination diets on AD. The prevalence of food allergies in patients with AD has been reported to be as high as 50.7%.207 A significant portion of atopic dermatitis (AD) patients report restricting specific foods they suspect might be causing reactions, hoping that modifying their diet will alleviate symptoms. Up to 75% of AD patients have tried dietary modifications to manage their disease, with only half seeking prior consultation from a healthcare professional or dietitian.208,209
Numerous studies have explored potential food-related risk factors for the development of atopic dermatitis (AD) or triggers for its symptoms. In a study using the Korean National Health and Nutrition Examination Survey, Park et al reported that the consumption of meat, instant noodles, and processed foods was linked to an increased prevalence of AD.210 Similarly, Lim et al found a strong association between a high intake of burgers and fast food and an elevated risk of chronic and severe AD, while an increased consumption of fruits and vegetables was associated with a reduced risk.211 In a 2017 survey focusing on patient-reported outcomes in dietary modifications, the most commonly trialed dietary modifications included junk foods (68%), dairy (49.7%), and gluten (49%). Notably, the most significant skin improvement occurred when removing white flour products (53.6%), gluten (51.4%), and nightshades (51.4%).212
Studies on gluten intolerance and gluten-free diets in AD have yielded inconsistent results. A cross-sectional study found that AD was associated with a significantly higher prevalence of celiac disease on multi-variate analysis.213 However, a cohort study did not find a significant association between amount of dietary gluten intake and atopic dermatitis in adult women.214 Similarly, in a questionnaire study between celiac and non-celiac controls, there was no significantly increased risk of AD among celiac patients. However, celiac patients with AD most frequently reported positive responses from gluten-free diets.215 Appropriate testing for adverse food reactions is important, albeit challenging. Despite the frequent implementation of dietary changes, research indicates that 50-90% of patient-perceived food reactions are not allergies.216 To minimize subjective influences on observed outcomes, double-blind placebo-controlled oral food challenges are the gold standard for diagnosing food allergies.216 Patients are recommended to avoid food triggers if true IgE-mediated allergies are found.217
Historically, empiric elimination diets were proposed as a beneficial approach to diminish AD flare-ups. However, more recent studies and guidance documents have increasingly discouraged the use of elimination diets. A 2008 Cochrane review noted some benefits in employing an egg-free diet for infants with suspected egg allergies and positive IgEs to eggs. Nevertheless, limited evidence supports the use of exclusion diets in individuals with atopic eczema, possibly due to the absence of true food allergies to the excluded foods.218 Excessively restrictive diets have led to nutritional deficiencies and malnutrition.219 Unnecessary food elimination diets may lead to iatrogenic food allergies, causing the emergence of new IgE-mediated sensitivities to previously tolerated foods and posing the risk of anaphylaxis.220
There is a growing body of literature suggesting a reciprocal relationship between obesity and AD. Both conditions exhibit common pathologic features, including inflammation, insulin resistance, and leptin resistance.221 Obesity has been shown to predispose individuals to AD development and worsen AD symptoms, whereas AD is associated with an increased risk of obesity.221–224 Furthermore, obesity is linked to heightened resistance to anti-inflammatory treatments.225
Existing literature indicates that weight reduction can alleviate AD symptoms. In 2020, Jung et al conducted a prospective randomized controlled study focusing on the therapeutic effects of weight loss and serum adipokine levels in AD. Obese patients (BMI > 25 kg/m2, n = 20) were randomly assigned to either weight maintenance and weight reduction groups, while non-obese (n = 20) AD patients served as controls. Significantly different serum adipokine levels were observed between obese and non-obese patients, and there was a positive correlation between AD severity (EASI score) and pruritus visual analog score (VAS). BMI and EASI also exhibited a positive correlation, and weight reduction decreased EASI scores among obese AD patients.226
Similarly, a 2018 case report highlighted how dietary control and exercise contributed to symptomatic improvement in a patient with refractory symptoms despite one-year treatment with antihistamines, topical steroid, and cyclosporine. After 12 weeks, the patient’s BMI reduced from 26.81 kg/cm2 to 20.64 kg/cm2, waist circumference decreased from 82 cm to 65 cm, EASI score decreased from 16.8 to 6.6, and VAS score decreased from 7 to 4. These changes were accompanied by visible improvements in skin lesions.227
Research evaluating the impact of vegetarian diets on AD has yielded conflicting results. A 2023 questionnaire study involving young adults from Singapore and Malaysia (aged 19-22, n = 13,561) found a negative association between moderate-to-high intake of plant-based foods with chronic or moderate-to-severe AD.228 Conversely, a 2022 Dutch questionnaire study (n = 56,896) found no associations between AD and physical activity, diet quality, and vegetarian or vegan diets. Interestingly, the Dutch study reported a positive association between moderate-to-severe AD and Class I obesity, a condition linked with dietary factors.229
In 2001, Tanaka et al conducted an open-trial study on the effects of a standardized vegetarian diet on AD improvement, utilizing the SCORAD method for symptomatic changes while measuring serologic and immunologic parameters (n = 20). Following a two-month treatment period, significant reductions were observed in the SCORAD index, LDH5 activity, and peripheral eosinophils. Moreover, there was a significant decrease in PGE2 production from mononuclear cells, although serum IgE levels remained unchanged.230
In 2017, Nosrati et al conducted a cross-sectional survey investigating dietary modifications, perceptions, and patient-reported outcomes among individuals with AD. The findings revealed that 79.9% of patients incorporated new foods into their diets. Of the 63 respondents (37.3%) who reported trialing a specific diet, the most implemented diets were a gluten-free diet (n = 25, 39.7%), vegetarian diet (n = 17, 27%), and Paleo diet (n = 11, 17.5%). The most frequently added items were vegetables (62.2%) and fruits (57.8%), and the greatest improvement in skin occurred when adding vegetables (40/84, 47.6%) and organic foods (17/43, 39.5%).212
Intrauterine sensitization and exposure during pregnancy has been suggested to influence the early development of immune systems in infants, thereby playing a role in the etiology of childhood allergic diseases.231,232 Consequently, studies have been conducted to evaluate the effects of maternal diets on the development of AD during childhood. In 2023, Su et al reported that children of mothers who adhered to a vegetarian diet during pregnancy exhibited a reduced risk of developing AD before reaching 18 months of age (OR 0.65, 95% CI 0.45-0.93, p = 0.018).233 Long-term follow-up studies are needed to better characterize the impact of a mother’s diet on allergic conditions.
Probiotics have been suggested for AD management based on observations of distinct differences in the intestinal microbiota between individuals with and without AD. However, studies have found mixed evidence to support their use as a treatment. Recently, a 2022 meta-analysis suggested that use of probiotics decreased Scoring Atopic Dermatitis scores significantly in adults with atopic dermatitis.234,235
Fish oil has additionally been suggested for AD management, as essential fatty acid deficiencies were postulated to be a factor involved in AD pathogenesis.236 Mendelian randomization studies have indicated an association between lower levels of n-3 fatty acids and a reduced risk of AD.237 Nevertheless, randomized controlled trials have produced varying outcomes, underscoring the need for larger and more robust studies on the role of oral fatty acid supplementation in AD.238
Hempseed oil, recognized as a source for omega-6 and omega-3 PUFAs, has been evaluated for possible benefits in AD. In a randomized single-blinded crossover study, 20 adults (aged 25-60 years) were allocated to either the hempseed oil or olive oil (placebo) groups. Results revealed improvements in skin dryness and itchiness, reduced usage of dermatologic medications, and decreased skin transepidermal water loss in the hempseed oil group. Furthermore, essential fatty acids such as linoleic acid, alpha-linolenic acid, and gamma-linolenic acid increased in the hempseed oil group, without a corresponding increase in arachidonic acid.239 Larger randomized controlled trials are needed to evaluate the potential benefits of hempseed oil in treating AD. (See Table 5).
194
III
Investigated association between dietary habits and AD in 17,497 adults in the 2009-2011 Korean National Health and Nutrition Examination Survey (KNHANES)
Atopic dermatitis
The meat and processed food pattern was associated with a significantly higher OR for atopic dermatitis than the low consumption group. Increased atopic dermatitis was most closely associated with instant noodles, whereas the groups with high intake of rice and kimchi exhibited lower ORs compared to the low intake group
Consuming instant noodles, meat and processed foods was associated with increased prevalence of atopic dermatitis, whereas consuming rice and kimchi, and coffee was associated with decreased prevalence of atopic dermatitis
195
III
Association between the dietary intake of 16 food types and AD manifestations using Singapore/Malaysia Cross-sectional Genetics Epidemiology Study (SMCGES) population. Dietary habits profiles of 11,494 young Chinese adults were assessed by an investigator-administered questionnaire
Severity of atopic dermatitis
A moderate Quality of Diet based on Glycaemic Index Score (QDGIS) class was significantly associated with a lower odd of AD and moderate-to-severe AD. A good QDGIS class was only significantly associated with a lower odds of chronic AD. Among high GI foods, frequent consumption of burgers/fast food was strongly associated with an increased risk of chronic and moderate-to-severe AD. Among low GI foods, increased intake frequencies of fruits, vegetables, and pulses decreased the odds of AD. Also identified significant associations between frequent seafood, margarine, butter, and pasta consumption with an increased odds of AD despite them having little GI values
While genetic components are well-established in their risks associated with increased AD prevalence, there is still a lack of a focus epidemiology study associating dietary influence with AD
196
IV
169 AD patients were surveyed with a 61-question survey about dietary modifications, perceptions, and outcomes
Skin improvement
Eighty seven percent of participants reported a trial of dietary exclusion. The most common were junk foods (68%), dairy (49.7%) and gluten (49%). The best improvement in skin was reported when removing white flour products (53.6%), gluten (51.4%) and nightshades (51.4%). 79.9% of participants reported adding items to their diet. The most common were vegetables (62.2%), fish oil (59.3%) and fruits (57.8%). The best improvement in skin was noted when adding vegetables (47.6%), organic foods (39.5%), and fish oil (35%)
Since dietary modifications are extremely common, the role of diet in AD and potential nutritional benefits and risks need to be properly discussed with patients
198
III
63,443 participants, food frequency questionnaires were used to calculate gluten content of participants' diet every 4 years (1995-2013)
Risk of atopic dermatitis
Increased gluten intake was not associated with increased risk of AD
Findings do not support the amount of dietary gluten intake as a risk factor for atopic dermatitis in adult women
210
IV
40 AD outpatients, obese patients divided into a weight maintenance and weight reduction group, collected data including BMI, Eczema Area and Severity Index (EASI), and visual analogue scale for pruritus.
Eczema Area and Severity Index (EASI) and visual analogue scale for pruritus
In the weight reduction group, there was a significant improvement in the EASI score, however, no significant improvement was determined in the weight maintenance group. BMI and EASI showed positive correlation
Weight reduction was associated with significant improvement of AD symptoms
211
IV
20-year-old obese F with AD prescribed Lorcaserin 10 mg BID and exercise and followed for 12 weeks recording BMI, waist circumference, EASI, VAS for pruritus, and physical exam
EASI, visual analogue scale for pruritus, skin lesions on physical exam
At first visit, body mass index (BMI) was 26.81 kg/cm2 (73 kg, 165 cm), waist circumstance was 82 cm, Eczema Area and Severity Index (EASI) score was 16.8, and visual analogue scale (VAS) for pruritus was ‘7.’ After 12 weeks, BMI was 20.64 kg/cm2 (56.2 kg), waist circumstance was 65 cm, and symptoms had improved. EASI score was 6.6, VAS was ‘4,’ and skin lesions improved
Weight loss decreased severity of AD
212
III
Standardized questionnaire following the International Study of Asthma and Allergies in Childhood (ISAAC) guidelines was investigator-administered to a clinically and epidemiology well-defined allergic cohort
Atopic dermatitis exacerbation
Moderate-to-high intake of plant-based foods conferred a negative association for chronic and moderate-to-severe AD. Meat and rice and probiotics, milk and eggs were not significantly associated with AD exacerbation. While frequent adherence to high-calorie foods increased the associated risks for moderate-to-severe AD, having a higher adherence to plant-based foods diminished the overall associated risks
Frequent adherence to plant-based foods was associated with reduced risks for AD exacerbation in young Chinese adults from Singapore/Malaysia. This provides the initial evidence to support the association between dietary factors and AD. Further research is needed to better understand the mechanisms underlying diet and AD exacerbations
214
IV
20 patients with AD, evaluated SCORAD index and serological and immunological parameters after 2 months of treatment with a certain vegetarian diet
Severity of dermatitis
After a 2-month treatment, the severity of dermatitis was inhibited, as assessed by SCORAD index and serological parameters including LDH5 activity and a number of peripheral eosinophils. A sharp reduction in eosinophils and neutrophils was observed prior to improvement in the skin inflammation. In addition, PGE2 production by peripheral blood mononuclear cells was reduced by this treatment. In contrast, serum IgE levels did not change during the same period
This treatment may be useful for treatment of adult patients with severe AD
217
IV
Case control using Taiwan Birth Cohort Study database with 4,200 mother–child pairs in the database, 20,172 completed face-to-face interviews at 6 and 18 months. Employing a 1:10 matching strategy based on maternal age, education level, and child sex, 408 mothers who followed a vegetarian diet during pregnancy were matched with 4080 nonvegetarian mothers. This resulted in a final dataset of 4488 subjects.
408 mothers following a vegetarian diet during pregnancy compared to 4080 nonvegetarian mothers
Risk of developing AD
292 (1.8%) mothers who adhered to lacto-ovo vegetarianism and 116 (0.7%) mothers who adhered to veganism, totaling 408 (2.4%) vegetarians during pregnancy. Compared to children of nonvegetarian mothers, children of mothers who followed a vegetarian diet during pregnancy showed a lower risk of developing AD before 18 months of age
A vegetarian diet during pregnancy may lower the risk of AD in children
223
II
20-week randomized single blind crossover study with atopic patients comparing dietary hempseed oil and olive oil, measuring fatty acid profiles and skin dryness, itchiness, usage of dermal medications, and TEWL
Fatty acid profiles, skin dryness, itchiness, use of dermal medications, TEWL
levels of both essential fatty acids (EFAs), linoleic acid and alpha-linolenic acid, and gamma-linolenic acid increased in all lipid fractions after hempseed oil, with no significant increases of arachidonic acid in any lipid fractions after either oil. Intra-group TEWL values decreased, qualities of both skin dryness and itchiness improved and dermal medication usage decreased after hempseed oil intervention
Dietary hempseed oil caused significant changes in plasma fatty acid profiles and improved clinical symptoms of atopic dermatitis
Overall, the promising yet limited body of literature regarding dietary intervention and its effects on symptom severity and management of inflammatory skin diseases including psoriasis, atopic dermatitis, hidradenitis suppurativa, and acne vulgaris suggests a positive outlook for its use as a primary or adjuvant treatment modality for these selected skin diseases. We conclude that dietary intervention may be an effective treatment for reducing symptom severity related to skin disease. Future studies should compare dietary intervention versus placebo for selected skin diseases to establish more robust associations.
This paper highlights an exciting topic of research with further prospective research necessitated by both community and academic dermatologists. As such, small and large-cohort randomized controlled trials are warranted in order to establish dietary intervention as a treatment option for dermatologists caring for patients with psoriasis, atopic dermatitis, hidradenitis suppurativa, and acne vulgaris. Subsequent research may focus on a personalized approach to dietary intervention. Currently, use of Mediterranean diet is one of the most evidence-based diets used as an adjunct to medical therapy for management of inflammatory dermatoses. For dermatologists recommending dietary intervention as a potential adjunct treatment, it is important to first ask patients about their individual needs as well as their attitudes/perceptions towards use of dietary intervention in the management of their skin disease. Dermatologists should recommend evidence-based dietary regimens and take an interdisciplinary approach, involving a dietician if deemed necessary along with setting realistic expectations for patients.
Ms. Shah, Ms. Chang, Ms. Tran, and Ms. Sadur have no conflicts of interest. Dr. Choudhary is a speaker at Regeneron Sanofi speaker bureau. Dr. Lio reports being on the speaker’s bureau for AbbVie, Arcutis, Eli Lilly, Galderma, Hyphens Pharma, Incyte, La Roche-Posay/L’Oréal, Pfizer, Pierre-Fabre Dermatologie, Regeneron/Sanofi Genzyme, Verrica; reports consulting/advisory boards for Alphyn Biologics (stock options), AbbVie, Almirall, Amyris, Arcutis, ASLAN, Bristol-Myers Squibb, Burt’s Bees, Castle Biosciences, Codex Labs (stock options), Concerto Biosci (stock options), Dermavant, Eli Lilly, Galderma, Janssen, LEO Pharma, Lipidor, L’Oréal, Merck, Micreos, MyOR Diagnostics, Regeneron/Sanofi Genzyme, Sibel Health, Skinfix, Suneco Technologies (stock options), Theraplex, UCB, Unilever, Verdant Scientific (stock options), Verrica, Yobee Care (stock options). In addition, Dr. Lio has a patent pending for a Theraplex product with royalties paid and is a Board member and Scientific Advisory Committee Member emeritus of the National Eczema Association. This study received no funding.
V.K.S contributed to idea curation, data curation, data analysis, manuscript writing and reviewing. S.J.C. contributed to data curation, data analysis, manuscript writing. T.T. contributed to data curation, data analysis, manuscript writing. A.S. contributed to data curation, data analysis, manuscript writing. P.A.L. contributed to manuscript reviewing. S.C. contributed to idea curation and manuscript reviewing.
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