Last year, a team of researchers from the University of California-San Francisco School of Medicine’s Department of Dermatology published the results of a national survey designed to gauge the influence of diet on psoriasis. More than 1,200 members of the National Psoriasis Foundation responded to the survey’s 61 questions, with revealing and even surprising results.
Published in Dermatologic Therapy in May 2017, the survey findings offer a vivid picture of patients’ dietary practices, along with foods that seem to intensify their psoriatic skin symptoms and those that quell them.
The researchers found that people with psoriasis consume less sugar, dairy and whole grain fiber than people who don’t have the disease. More than half of the survey participants reported that reducing alcohol, gluten, and nightshades – members of the plant family that includes tomatoes, potatoes, eggplant and peppers – led to noticeable improvement in their symptoms. Adding fish oil, vegetables, and vitamin D proved helpful as well.
Respondents also named several special diets as particularly effective in alleviating their symptoms: the Pagano diet (based on the principle that psoriasis is caused by a toxic buildup or “leaky gut”), the vegan diet, and the Paleo diet. The gluten-free, low carbohydrate/high protein, Mediterranean and vegetarian diets were also seen to be helpful.
John Y.M. Koo, M.D., director of the Psoriasis, Phototherapy and Skin Treatment Clinic at UCSF and a co-author of the study, notes that the common thread running through these very different diets is that they lead to weight loss.
“The evidence may not yet be available regarding which of these diets is most effective for psoriasis patients, but one thing has been observed to be of universal benefit: losing weight,” Koo says. “To the extent that the Paleo or vegan or gluten-free diet helps people do that, they’re worth trying.”
What this means for your diet
The data gleaned from the survey aren’t evidence in the strict sense, says Koo. Nonetheless, he believes the results are meaningful. “Because the survey is based on reports from real life – on what’s working for patients and what isn’t – the findings can be empowering for them,” he says. “Patients can decide to eliminate one of the triggers on the list or follow one of the top-ranked diets in the survey and track their response over time.”
To do that, people should keep a food journal, commit to a trial-and-error approach, and “remain open-minded and aware that what works for one person may not work for another,” says Wilson Liao, M.D., the study’s senior author and a member of the NPF medical board. “They should also consider working with a nutritionist, or a physician with a strong background in nutrition, to design a suitable diet in light of the individual’s preferences and medical history.”
Both Liao and Koo remind us that psoriasis isn’t one single disease. “Some people develop psoriatic arthritis. Some have elevated levels of the inflammatory cytokine TNF, while others have elevated IL-17,” says Koo, explaining that different drugs work for people with different subtypes of the disease, such as plaque or guttate. It’s reasonable, he says, to speculate that people with different subtypes of psoriasis might respond to different dietary approaches as well. Matching nutrition with disease subtype is just one intriguing challenge for future research.
“Ideally,” Liao says, “the data from the survey could be used to design the rigorous clinical trials we need to fully elucidate the link between diet and psoriasis.”
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