An Update on the Role of Dietary Change as a Treatment Strategy for Skin Disease
Abstract and Introduction
Abstract
An increasing body of research indicates that dietary change may serve as a component of therapy for certain skin conditions. This includes conditions such as acne, atopic dermatitis, aging skin, psoriasis, and rosacea. Certain nutrients, foods, or dietary patterns may act as disease “triggers”, while others may prove beneficial. Avoidance or elimination diets may be helpful in some conditions, although testing may be recommended first. In terms of beneficial effects, an eating pattern that emphasizes the consumption of whole foods over highly processed foods may help in the treatment of certain skin conditions, and will certainly help in the prevention of associated co-morbidities.
Introduction
Dietary change has long been considered an important treatment strategy for certain skin conditions. For example, dermatologists have long discussed the role of dietary triggers in rosacea and insulin resistance in acanthosis nigricans. As an increasing body of research has demonstrated, dietary change may play a role in treatment strategies for other skin diseases as well.
In this review, we focus on five major skin conditions for which dietary change may be advised as one component of treatment. As a quick Internet search will reveal, there is much misinformation on the link between skin and diet. Some recommendations are ineffective, while others are potentially harmful, such as untested dietary supplements or severely restrictive elimination diets. It is critical, therefore, that physicians be well-informed in this area in order to provide evidence-based recommendations.
In this article, we review information on specific nutrients, foods, or dietary patterns that may act as disease “triggers”, as well as those that may prove beneficial in therapy. This review provides a synopsis, highlighting promising research findings.
Triggers
The strongest evidence to date on dietary triggers for acne is for high-glycemic-load diets. In a randomized controlled trial (RCT), acne patients demonstrated significant improvement after 12 weeks of a low-glycemic-load diet.[1] Later studies documented that this dietary pattern resulted in lower androgen bioavailability and altered skin sebum production.[2,3] In another RCT, a 10-week low-glycemic-load diet improved acne, and histopathological exam revealed decreased skin inflammation and reduced sebaceous gland size.[4]
Some studies have demonstrated an epidemiologically weak association between acne and dairy consumption, possibly more so with skim milk.[5–7] While further research is needed, it may play a role in some patients, as in a report of five teenagers who developed treatment-resistant acne after starting whey protein supplements.[8]
Beneficial Measures
Studies in humans are limited and, therefore, despite promising in vitro, animal, or anecdotal reports, recommendations for foods or supplements containing probiotics, omega-3 fatty acids, zinc, antioxidants, fiber, and vitamin A cannot be made with certainty at this time.[9] Omega-3 fatty acids warrant further study; in one 10-week RCT, omega-3 fatty acid supplements and gammalinolenic acid supplements both resulted in clinical and histopathological improvement in acne lesions.10 Probiotics warrant further study as well; in one RT, minocycline with probiotic supplementation resulted in a lower total lesion count as compared to antibiotics alone.[11]
Zinc bears special mention, as it has been studied in several RCTs. While some trials have not been successful, others have demonstrated efficacy in acne treatment.[12,13] Further research is warranted, as published trials have utilized multiple dosages and forms of zinc, including zinc gluconate, zinc sulphate, and methionine-bound zinc, among others. Some formulations have better absorption and result in less gastrointestinal side effects. Other factors that impact zinc absorption include age and meal components.[14] In addition, some successful trials have utilized zinc in combination with other components, such as antioxidants and lactoferrin.[15,16] Future research must account for these multiple factors.
Diet and Aging Skin
Triggers
For patients who present for cosmetic treatment of aging skin, lifestyle factors that impact this process are an important aspect of treatment. While smoking and sun protection are commonly reviewed, dietary factors should be as well.
While it has long been recognized that diabetics experience poor wound healing, there is now a greater recognition that these effects on collagen can promote skin wrinkling. Higher levels of blood sugar can result in the production of advanced glycation end products (known as AGEs) via glycation and cross-linking of collagen fibers, which ultimately results in a loss of elasticity.[17] Consumption of pre-formed AGEs, created during certain cooking processes such as deep-frying, can also be detrimental.[18]
Even in non-diabetics, effects on collagen may be seen. Even after accounting for degree of sun damage and smoking, as study subjects’ blood glucose level increased, their perceived age increased.[19]
Beneficial Measures
Many laboratory and animal studies have found that multiple different antioxidants (AOs), found in foods ranging from various fruits and vegetables to tea leaves and seeds, act to limit the damaging cutaneous effects of ultraviolet (UV) radiation.[20] Experimental human studies of a few AOs have noted the same, as in one study in which subjects consuming tomato paste daily for 12 weeks experienced less UV-induced erythema, as well as lower levels of UV-induced matrix metalloproteinase.[21] It is important to note that research indicates AOs consumed via dietary sources appear to function in a different fashion than those found in isolated supplements.[22]
Other human studies suggest that a diet high in phytonutrients can limit photodamage. One study reported higher intake of vegetables, legumes, and olive oil appeared to protect against actinic damage.[23] In another study of over 4000 women, patients’ skin was analyzed for features of skin aging. After controlling for other factors, a diet reported as high in potassium and vitamins A and C correlated to fewer wrinkles.[24]
Diet and Psoriasis
The importance of diet should be emphasized to all psoriasis patients, primarily due to the higher risk of comorbid conditions, including diabetes, hypertension, and cardiovascular disease, that may be prevented or ameliorated by dietary approaches.[39] In addition, dietary change leading to weight loss has resulted in better treatment efficacy, as well as improved psoriasis area and severity index (PASI) scores in some patients.
Triggers
It is well recognized that smoking and increased alcohol intake are associated with psoriasis, and all psoriatic patients should be advised of their potential role.[40,41]
Dietary factors may also play a role. Gluten-containing foods may act as a trigger in some patients, and testing for celiac antibodies is warranted in those who report gastrointestinal symptoms. While estimates vary, one large study found a 2.2 fold higher risk of celiac disease as compared to matched controls, while a meta-analysis found a 2.4 fold higher risk of certain celiac antibodies.[42,43] In such patients, a gluten-free diet may result in psoriasis improvement, as demonstrated in small trials and case reports, although further studies are required to confirm.[43,44]
Beneficial Measures
In a systematic literature review, increased severity of psoriasis appeared to correlate with a higher body mass index (BMI), although the authors noted the difficulty in determination of temporality due to study designs.[45] It is believed that obesity likely predisposes to psoriasis, and vice versa.[46] While the reasons for this are multifactorial, it has been shown that weight loss can improve response to systemic psoriasis therapies and improve disease severity.
An excellent review article summarizes the effects of weight loss interventions in psoriasis.[47] In a meta-analysis of five RCTs of lifestyle intervention via diet or exercise in overweight or obese psoriasis patients, a greater reduction in PASI score was seen in weight loss intervention groups.[48] In a limited number of case reports and retrospective studies, some obese patients have experienced significant improvements in psoriasis following gastric bypass surgery.[49]
Conclusion
This article is intended as a general overview. There are several other conditions (not touched upon here) for which dietary intervention may be considered. For example, emerging research indicates that patients with hidradenitis suppurativa have a higher risk of adverse cardiovascular events, which may necessitate dietary change.[60] In the arena of prevention, research continues into the role of diet and supplement use in skin cancer prevention. As research continues, dietary interventions may play a role in other dermatologic diseases as well.
The five conditions reviewed here are very disparate, and yet patients with each often seek dietary advice. In discussing the link between skin and diet, it is important to recognize and convey the limitations of nutritional research. Specifically, such research may not lead to definitive answers applicable to every patient, but rather general recommendations.
This is in part due to the notable variability of individual responses to different foods and nutrients, as in marked differences in blood glucose responses to the same quantity of carbohydrates.[61] Confounding factors present a notable research challenge, as does the fact that many health effects may take months to years to manifest, which makes valid controlled dietary trials extremely challenging. Despite these challenges, nutritional research can indicate directions for further study, or add to an increasing body of evidence to support specific recommendations.
Based on research findings to date, certain dietary recommendations are suitable for patients with multiple different types of skin disease.
- The results of research support the promotion of eating patterns over specific foods or nutrients.
- An eating pattern that emphasizes the consumption of whole foods over highly processed foods may help in the treatment of certain skin diseases. It will certainly help in the prevention of associated comorbidities.
