Adults with psoriasis and/or psoriatic arthritis may benefit from specific dietary interventions. This finding is the bottom line of the new dietary recommendations from the National Psoriasis Foundation (NPF) Medical Board, which were published June 20 in JAMA Dermatology. The dietary interventions are intended to supplement standard medical therapies.1
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For the review, the authors identified 55 studies that met the inclusion criteria. The studies included 77,557 individuals, 4,534 of whom had psoriasis. Although a small number of pediatric patients was included in the studies, the authors felt the data were insufficient to make recommendations for pediatric psoriasis patients. Additionally, they note some of the studies that form the basis of the recommendation are limited because they were not randomized, blinded or controlled.
Although physicians should always recommend weight reduction for overweight patients, such recommendations are especially beneficial for patients with psoriasis. Excess body weight is associated with increased incidence and severity of psoriasis symptoms. Thus, the guidelines strongly recommend weight reduction via hypocaloric diets for patients with body mass index greater than 25, who are considered overweight or obese. The authors emphasize the recommendation is for weight loss from dietary interventions as opposed to exercise or surgery. They also note that diet alone may be insufficient to maintain psoriasis remission, and patients should continue medical therapies after weight loss. Although the NPF Medical Board does not recommend a specific diet, it highlights the Ornish and South Beach diets, while acknowledging the long-term benefit of these diets on psoriasis severity is uncertain.
In the recommendations, the NPF Medical Board explains that psoriasis is associated with an increased risk of several autoimmune diseases, including celiac disease. Thus, it recommends that, in addition to weight reduction, patients who test positive for markers of gluten sensitivity should begin a gluten-free diet. It notes that because higher gluten-specific antibody levels are associated with greater psoriasis severity, a gluten-free diet may not only improve gastrointestinal symptoms, but also reduce the severity of psoriasis in patients with confirmed celiac disease. However, the Medical Board does not go so far as to recommend universal screening of adults with psoriatic diseases for serologic markers of gluten sensitivity due to concerns about the high rate of false positive results from serological tests.
Many patients with psoriasis use dietary supplements and believe supplements decrease their disease severity. When the NPF Medical Board investigated the role of supplements in psoriasis treatment, it found only low-quality data sets. Additionally, when it looked specifically at data on the use of omega-3 fatty acids (e.g., fish oil), it found little evidence to support their use. An international panel of experts has identified an ideal omega-6 to omega-3 ratio of 1.8:1, but the typical Western diet has a ratio of 15–20:1. Patients often take fish oil supplements to improve their ratio. But studies evaluating the use of oral fish oil in psoriasis patients have yielded conflicting results. Thus, the guidelines do not recommend oral fish oil as treatment. It does, however, weakly recommend vitamin D supplementation for patients with psoriatic arthritis.