An appetite for healthy skin

By Emily Margosian, assistant editor, November 1, 2020

You are what you eat — more than just a mantra, the phrase encapsulates a growing public desire for food-based solutions to targeted health outcomes. However, mixed media messaging about "skin superfoods" and miracle supplements can create unrealistic patient expectations about the impact of diet on the skin. While many dermatologists have likely fielded hopeful questions from patients about dietary modifications as a means to manage or prevent their skin disease, answering these questions can be challenging given the extensive and sometimes conflicting amount of research on the topic.

Yet, a relationship between diet and the skin cannot be easily dismissed. “There are two big myths about diet in dermatology. The first is that diet has no impact on skin disease,” said Rajani Katta, MD, clinical professor of dermatology at the McGovern Medical School at the University of Texas Houston. “The second myth is that diet is the cause of all skin conditions. I really try to emphasize to my patients that for most skin conditions, diet may play a role, but it’s just one piece of the puzzle.”

This month, DermWorld speaks with subject matter experts to separate fact from fiction regarding the effects of diet on skin health and explores clinical pearls for recognizing potential dietary triggers of skin disease.

Managing patient expectations

Certain dermatology patients may be keener to seek out dietary solutions than others depending on the nature of their skin condition. According to Peter Lio, MD, clinical assistant professor of dermatology and pediatrics at Northwestern University, it is not uncommon for atopic dermatitis patients to associate their diet with the severity of their skin disease. “Many patients are convinced that food is one of the root causes of their eczema. Sometimes patients want to avoid certain foods to test this hypothesis, and historically, I’d say this is fine as long as overall nutrition is not impacted,” he said.

Setting realistic expectations with patients can also be a challenge, suggests New York dermatologist Reena Rupani, MD. “One huge misconception is that, if you fix the diet, you eliminate the disease,” she explained. “This is only true in the most limited cases — dermatitis herpetiformis related to celiac disease being one such instance. Fundamentally, genetics plays the biggest role in disease determination, and that factor is mostly out of our control,” she advised. “By the same token, however, we are what we eat! I like to talk to my patients about how diet is one important component of the complicated ‘human condition,’ along with exercise, stress management, mindfulness, and limiting exposure to toxins.”

Diet and dermatology: What does the evidence show?

While some dietary triggers of dermatologic disease are well-established, others are not well-supported by evidence. In some cases, a patient’s avoidance of certain foods may show no discernible improvement in their skin condition — or in a worst-case scenario, result in an increased risk of developing anaphylaxis or nutritional deficiencies (J Am Acad Dermatol 2014;71: 1039.e1-12). However, insight into sometimes-overlooked aspects of patients’ diets can provide valuable context for dermatologists when confronting otherwise puzzling disease flares, and with careful management, lead to improvement.

Navigating these nuances of diet is one of the many challenges faced by dermatologists, said Vivian Shi, MD, associate professor of dermatology at the University of Arkansas for Medical Sciences. “Different skin conditions may require an individualized dietary plan; what works for one person’s skin condition may actually worsen another’s,” she explained. “This has really put nutrigenomics and nutrigenetics — the studies of how food and our genes interact with each other to ultimately influence our skin health — at the forefront of nutritional research.”

Atopic dermatitis

Patients often report food as an exacerbating factor in their atopic dermatitis, sometimes adhering to a variety of exclusion diets in an attempt to control their skin disease. “In children, I have seen some dangerously extreme diets that can actually be damaging to their health,” said Dr. Lio. “More recently, I have begun to worry that excluding certain foods may actually be a bad idea for some patients, as a recent paper has demonstrated an increased risk of developing anaphylaxis and other acute immunoglobin E (IgE)-mediated reactions. So, ironically, the very thing we feared — a reaction to a food — can be manifested by trying to avoid it, at least in some cases.”

“I think that keeping a food journal and correlating it with symptoms is helpful for many. I try to discuss this and say that we want to be as systematic as possible, ideally working with an allergist who has done appropriate testing, and a dietician who can help ensure good nutrition.”

─ Peter Lio, MD

However, Dr. Lio concedes that in certain cases, the elimination of a particular dietary trigger does appear to improve the severity of patients’ atopic dermatitis. “They typically have more than just an eczema flare-up with those foods, often some gastrointestinal issues as well. For them, they are lucky when they find the food or foods, and do much better when avoiding them,” he said. “However, even for those patients, I find that rarely is the eczema totally gone. The foods seem to be more like triggers than a true root cause.” Dr. Lio theorizes that diet’s impact on atopic dermatitis may operate on a sort of sliding scale depending on its severity at a given time. “Remarkably, for the majority of my patients, just getting the skin better seems to allay these concerns,” he said. “I often think of it in terms of a threshold: if you are in a bad mood, someone simply saying ‘good morning,’ can upset you. If you’re in a great mood, someone stepping on your foot doesn’t even dampen your spirit. It may be similar with the skin — when things are bad and flared, perhaps smaller insults can make things worse, including some foods. Once better, many of these small things seem to not bother the skin in the same way, as if the threshold is now raised.”

Dr. Lio counsels patients concerned about their diet’s impact on their skin to keep a record of what they eat for a greater sense of control and potential nutritional benefits. “I think that keeping a food journal and correlating it with symptoms is helpful for many. I try to discuss this and say that we want to be as systematic as possible, ideally working with an allergist who has done appropriate testing, and a dietician who can help ensure good nutrition.”

Pemphigus

Dr. Rupani advises that foods containing thiols, thiocyanates, phenols, and tannins can unexpectedly precipitate pemphigus in genetically predisposed patients. “A thiol is a sulfur compound which occurs in many foods, including garlic, onion, cabbage, coffee, chocolate, beans, chlorella, and coriander leaf,” she explained. “In one case report, heavy garlic consumption flared pemphigus in a 49-year-old man who was genetically predisposed with HLADR4+, resolved with a garlic-free diet, and then flared with re-challenge.”

Foods with high phenolic compounds, another potential dietary trigger for pemphigus, include common staples such as tomatoes, apples, peanuts, mangos, cashews, bananas, oranges, cocoa, colored fruits (such as red grapes and cranberries), and milk. Examples of food sources of condensed tannins, which can also exacerbate pemphigus in some patients, include coffee, tea, wine, grapes, several types of berries, barley, and herbs such as mint, basil, and rosemary. “Interestingly, in some cases even water can be a contributing factor to disease exacerbation,” said Dr. Rupani. “The high tannin content in Brazil river water, which typically decreases with urbanization as tannins are removed by chlorination, may be a reason for endemic fogo selvagem.”

“One clinical pearl is if a patient who is stable on medication suddenly has a disease flare, it could be revealing to ask about supplement intake.”

─ Reena Rupani, MD

According to Dr. Rupani, dermatologists may also want to question patients about their ingestion of dietary supplements in the event of an otherwise puzzling pemphigus flare-up. “Spirulina, a popular supplement, contains phycocyanin, which is a blue pigment protein that has been linked to pemphigus flares in a human case report, as well as in vitro animal and human studies,” she said. “One clinical pearl is if a patient who is stable on medication suddenly has a disease flare, it could be revealing to ask about supplement intake.”

Acne

While the causes of acne are multifactorial, heavy sugar and dairy consumption have emerged as common dietary culprits. “Dairy and sugar can increase serum levels of insulin and insulin-growth factor like-1 (IGF-1),” explained Dr. Shi. “These hormones can then increase keratinocyte proliferation in the hair follicles and increase lipid production in the sebaceous glands. Together, these events lead to follicular occlusion or comedone formation, which is the inciting event for acne development.”

The particular type of dairy consumed can further affect the level of acne irritation, suggests Dr. Lio. “I would say that one compelling area — and one that can be held up as pretty convincing, even to those most skeptical — is the connection between dairy products and acne, in particular skim milk,” he explained. “The thinking here is that whey protein in particular, and perhaps other aspects of milk as well, are pro-inflammatory and can contribute to elevating insulin-like growth factor-1, which has been shown to increase acne.”

Rosacea

Historically, the consumption of alcohol, spicy foods, and high-temperature foods have been reported as common triggers of rosacea. However, “Caffeine, cinnamon, niacin-containing foods such as turkey, and formalin-containing foods such as wet noodles and tofu, have also been implicated in rosacea,” said Dr. Shi. “Avoidance of trigger foods can decrease cutaneous neurosensory activation and blood vessel dilatation — together known as neurogenic vascular dilatation — to limit rosacea symptoms, such as burning, tingling, flushing, and telangiectasia.”

However, even well-established dietary triggers can be highly variable, said Dr. Katta, who advises that dermatologists and their rosacea patients avoid a one-size-fits-all approach to what they consume. “Even though we mention spicy food as a big trigger — and it is — it may only yield a reaction in maybe half, but certainly not 100%, of all rosacea patients. When you start to look at other foods, tomatoes for example, can also be a trigger for some patients with rosacea, but more along the lines of 20% or so,” she explained.

Lupus

Already a complex disease with a broad range of clinical and molecular presentations, more than 50 genes have been found to contribute to lupus, each with their own genetic or environmental triggers. “An interesting, and perhaps lesser-known, dietary culprit in systemic lupus is the common alfalfa sprout; specifically, L-canavanine, which is an amino acid that affects T-cell regulation of antibody synthesis and lymphocyte proliferation, and has been a reported factor in disease exacerbation in both experimental animal models as well as human case reports,” said Dr. Rupani.

While Dr. Rupani admits that this might appear to be a relatively esoteric detail, as most patients do not have a diet high in alfalfa sprouts, “L-canavanine has relevance as a common dietary supplement taken for its cholesterol-lowering benefits. This is yet another example of why it is important to obtain a thorough supplement history from our patients,” she explained.

Hidradenitis suppurativa (HS)

Once considered a rare disease mistakenly associated with poor patient hygiene, recent insights into the pathogenesis of HS have resulted in better understanding and management of the condition (Read more about the benefits of personalized treatment plans for patients with HS).

Part of this new individualized focus may involve diet as well, suggested Dr. Shi. “The role of dietary intervention in hidradenitis suppurativa is an exciting area. Our research found that sweet foods, complex carbohydrates, dairy, and high-fat foods tend to worsen HS, while vegetables, fruits, and white meat consumption tend to alleviate HS, although more research is needed to further explore the mechanisms of how these foods actually influence the disease,” she explained.

Dr. Shi also advises that adherence to a "Mediterranean diet" has been shown to have a positive impact, in addition to avoidance of Brewer’s yeast-containing foods, although dietary supplements should be carefully managed. “High-dose zinc and vitamin D supplementations have been shown to help, although zinc should be supplemented together with copper to avoid copper deficiency at 10:1 zinc to copper ratio. This is because zinc interferes with copper absorption in the intestines,” she cautioned.

Vitiligo

Despite limited evidence, potential links have been postulated between vitiligo and celiac disease. “There was a single case report of an Indian woman who failed all conventional therapy for vitiligo, but experienced complete resolution of her symptoms by adhering to a strict gluten-free diet; she had no symptoms of celiac disease, but was unwilling to re-challenge with gluten,” said Dr. Rupani.

However despite the intriguing report, strong evidence remains lacking. “Vitiligo and celiac disease share a general concept of autoimmunity in their pathogenesis, however the story with vitiligo is much more complicated, in that there is not a specific measurable antibody for diagnosis or monitoring disease progression,” explained Dr. Rupani. “Studies looking at seropositivity of celiac IgA anti-endomysial antibodies and IgA anti-tissue transglutaminase antibodies in patients with vitiligo have been mixed, and no conclusive linkage can be drawn.”

While vitiligo patients may express interest in a gluten-free diet — “Gluten has become a popular scapegoat,” acknowledged Dr. Rupani — she advises that dermatologists set the expectation that measurable skin improvement is unlikely.

Skin aging

The desire to slow — or even stop — the process of aging is deeply rooted in human nature. However, while no single food or lifestyle choice has yet to fully halt the passage of time, emerging research has suggested that a healthy diet may play a greater role in skin anti-aging efforts than previously anticipated. A recent JAAD population study found a healthy diet in Dutch women to be associated with fewer facial wrinkles (2019 May;80(5): 1358-1363.e2). “They had an independent assessment of how aged the skin looked, controlling for other variables such as sun exposure, weight, and smoking, that we know impact the aging of the skin,” said Dr. Katta. “What they found was that women who had a closer adherence to a healthy eating pattern had fewer wrinkles, whereas women who had eating patterns that involved a lot of red meat and processed snacks had more.”

Dr. Katta also cites diabetes prevention and careful control of glucose levels through healthy eating as an important facet of skin anti-aging. “One of the reasons diabetes is so bad for aging skin is because higher levels of blood sugar cause the creation of new compounds that damage collagen and make you lose elasticity,” she explained. “On the skin, we see that as wrinkles and sagging, but if you also think about collagen in your blood vessel walls, that elasticity is really important to reduce the risk of high blood pressure and heart disease. That’s why focusing on strategies to maintain collagen has so many implications for other health conditions as well.”

Diet and dermatology: Looking forward

Although the full story of how diet does — or does not — impact the skin is still being uncovered, Dr. Rupani anticipates dietary intervention playing a greater role in the management of skin disease in the future. “Right now, research on the microbiome and how it is affected by diet is what I find most compelling. The concept that emotional states might alter our normal intestinal microflora, increase intestinal permeability, and contribute to systemic and skin inflammation — a ‘gut/brain/skin’ hypothesis — dates back to 1930, but is now gaining resurgent interest in both research and popular press,” she explained. “On a more personal level, however, we all like thinking about our diets for a variety of reasons, not the least important of which is the sense of agency and perceived control we feel we can wield over this one factor in our lives. During the COVID-19 pandemic, there has been an explosion of online recipes, diet plans, food blogs, and published cookbooks, as we each grasp for that steadying element of control in this scary and uncertain time.”

“We all like thinking about our diets for a variety of reasons, not the least important of which is the sense of agency and perceived control we feel we can wield over this one factor in our lives. During the COVID-19 pandemic, there has been an explosion of online recipes, diet plans, food blogs, and published cookbooks, as we each grasp for that steadying element of control in this scary and uncertain time.”

─ Reena Rupani, MD

Dr. Lio agrees that although the science behind diet’s impact on the skin remains developing and imperfect, the important role food plays in daily life makes it a critical piece of any health puzzle. “There is literature that supports the idea that making a big change in diet can have a powerful effect on many conditions, from depression to irritable bowel disease. While some might say these are more akin to placebo effects, as a clinician, I do not deny that especially for complex, multifactorial diseases like atopic dermatitis, changing large patterns like this can be instrumental to breaking the vicious cycles that emerge with this condition,” he explained. “While the data is relatively scant, I truly believe that eating better overall has far-reaching beneficial effects that are sometimes difficult to quantify in the short time frame of most studies.”

Dr. Katta cites the specialty’s relative consensus on the connection between certain foods and acne exacerbation as foreshadowing further revelations to come. “When I was in training over 20 years ago and people would ask us about acne, we’d say ‘no, we haven’t been able to show a link between acne and diet.’ Over the last 10 to 15 years, we’ve seen numerous studies establishing that connection,” she recalled. “So, as we have the results of more research coming out every year, it’s starting to change how we practice and talk about these issues.”

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