Diet in Dermatology
Food can play a key role in managing psoriasis, atopic dermatitis, acne, rosacea, and aging skin.
While the effects of diet on the skin have long been recognized, the increased use of the internet for medical information has made it more imperative than ever that dermatologists serve as the authoritative voices on this subject. As any dermatologist can attest, patients are presented with a considerable amount of conflicting advice in this area, along with a plethora of misinformation. Dietary change may be used to reduce the risk of comorbidities or in the treatment of certain skin conditions,1 but counseling patients requires an individualized, nuanced approach, along with delineation of areas requiring further research, which makes education by a board-certified dermatologist critical. Dermatologists can also direct patients toward unbiased, authoritative, evidence-based sources for further information. While there are many links between diet and dermatology, this article focuses on the role of diet in psoriasis, atopic dermatitis (AD), acne, rosacea, and aging skin.
Framework: Review Risk of Comorbidities, Beneficial Dietary Changes, and Triggers
It is helpful to approach dietary recommendations in the setting of an overall framework. Initial discussions should review the risk of potential comorbidities. Patients with psoriasis, for example, are at increased risk for multiple systemic comorbidities, including cardiovascular disease (CVD), diabetes, and hypertension. Second, patients should be counseled on beneficial dietary recommendations, specifically eating patterns, foods, and/or nutrients that may be of benefit in the treatment of skin disease, such as the use of synbiotics in the treatment of AD. Finally, a review of “triggers” is important. Triggers are defined as eating patterns, foods, or nutrients that may worsen skin disease, such as high glycemic load diets in acne.
In counseling patients, the goal is to translate evidence-based research into recommendations that are specific, individualized, and actionable.
Diet and Psoriasis
Can dermatologists play a role in protecting our psoriasis patients? The answer to this question is a resounding “yes.” Psoriasis patients are at risk for multiple comorbid diseases, and dermatologists play an important role in educating patients and providing appropriate referrals (Table 1).
Multiple studies have now confirmed that psoriasis patients have a higher prevalence of comorbidities, including diabetes, hypertension, dyslipidemia, and obesity.2 Furthermore, psoriasis patients have an increased risk of CVD, even after adjustment for risk factors including hypertension, diabetes, and hyperlipidemia.3
Dietary change is critical to preventing these comorbidities. Evidence-based risk reduction strategies include the Mediterranean diet for the prevention of CVD4 and the DASH diet for the prevention of hypertension.5 For patients with prediabetes, certified diabetes prevention programs have been shown to achieve weight loss and to reduce the risk of progression to diabetes by 58%.6 These structured lifestyle intervention programs are covered by Medicare and some commercial insurance programs.
Beneficial Dietary Changes
In overweight and obese patients with psoriasis, weight reduction may improve cutaneous findings. In a systematic review of dietary recommendations for adults with psoriasis, the authors reviewed 55 studies7 and strongly recommended dietary weight reduction. In a separate meta-analysis looking specifically at 5 randomized controlled trials (RCT) of weight loss interventions, it was found that weight loss via diet or exercise interventions in overweight and obese patients led to a greater improvement in Psoriasis Area and Severity Index (PASI) scores.8 Separately, weight loss has also improved response to systemic therapies, as in a RCT of patients treated with cyclosporine.9
A quick perusal of Google search results shows many websites recommend gluten-free diets (GFD) to patients with psoriasis. This is likely due to case reports describing resolution of psoriasis with a GFD in patients with celiac disease. Given the popularity of this recommendation, it is especially important that dermatologists identify those patients who may benefit vs those who are unlikely to benefit from GFD.
Patients with psoriasis have an increased risk of celiac disease, with some studies estimating a 2.2-fold higher risk.10 Interestingly, small studies indicate that even patients without celiac disease may benefit from a GFD if they test positive for gluten antibodies. In 1 study, patients with IgA or IgG antibodies to gliadin who followed a GFD for 3 months experienced a significant decrease in mean PASI scores.11 By contrast, a comparison group negative for these antibodies did not experience improvements in PASI scores with a GFD.
Diet And Atopic Dermatitis
While further research is required, a recent population-based cohort study indicated a potential increased risk of CVD in patients with AD. In this study, the medical records of close to 400,000 adults with AD were compared to over 1.5 million matched controls. Patients with severe AD had a 40% to 50% increased risk of unstable angina, myocardial infarction, atrial fibrillation, or cardiovascular death.12 While more research is needed to confirm this potential increased risk, dermatologists should consider referral of patients with severe AD to their primary care physician for a history and physical. Early identification of risk factors including hypertension, diabetes, and dyslipidemia is important, while evidence-based dietary risk reduction strategies for CVD include the Mediterranean diet.4
Beneficial Dietary Changes
In a meta-analysis, the use of synbiotics showed promise in the treatment of AD in adults and children older than 1 year.13 Synbiotics are probiotics given with prebiotics. They may be of benefit as patients with AD have exhibited alterations in gut flora.14 Although promising, the individual studies reviewed utilized different bacterial strains, dosages, and duration of probiotic treatment, as well as different prebiotics. Importantly, there was also significant variability in individual response.14 While further research on supplementation is suggested, recommendations that encourage the growth of beneficial gut microbes are certainly warranted. This includes the consumption of fiber-rich prebiotic foods and may include probiotic foods, such as yogurt and kimchi.
Studies have also suggested that ingestion of certain polyunsaturated fatty acids may improve skin barrier function, as in a study that evaluated flaxseed oil supplementation for 12 weeks.15 This intervention resulted in less transepidermal water loss and less sensitivity to a known irritant. See Table 2 for more tips.
It is well recognized that AD is strongly correlated with food allergies, although the overall estimated prevalence of food allergy in children with AD has ranged widely.16 What is less clear is how often food allergies serve as an exacerbating factor in AD, although they clearly play a role in some patients. Studies indicate that those most likely to be impacted are infants and children with moderate to severe AD.17
When counseling patients, it is important to emphasize that there are at least 3 types of food allergies that may exacerbate AD, and likely more.18 While type 1 immediate-type, IgE-mediated reactions may occur minutes to hours following food ingestion, delayed eczematous reactions may occur as late as 48 hours after consumption.19 As the immunological mechanism of these delayed reactions is unknown, blood tests and skin prick tests are not adequate, and confirmation requires double-blind, placebo-controlled food challenges.17 The main food triggers for both reactions are milk, eggs, wheat, seafood, nuts, and soy. Systemic contact dermatitis, tested for by patch testing, may also result in a flare of dermatitis. Top triggers include foods related to fragrance additives/balsam of Peru, including tomatoes, citrus, and cinnamon.20
Diet And Acne
Beneficial Dietary Changes
Low glycemic load diets have resulted in acne improvement and beneficial effects on biochemical parameters. In one RCT, a 12-week study of 43 men resulted in a greater decrease in total lesion counts in those following a low glycemic load diet, along with a reduction of free androgen index and an increase in insulin-like growth factor binding protein.21 Later studies documented a decrease in skin sebum and histologic decrease in skin inflammation and sebaceous gland size.22,23 Despite these findings, patients may not recognize the role played by sugar and processed carbohydrates. In a small survey study of a highly educated patient population, 71% of respondents believed that fried or greasy foods were an acne trigger, while only 16% reported sugar as a potential trigger.24
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