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The National Psoriasis Foundation has released dietary recommendations for adults with psoriasis and psoriatic arthritis, based on a systematic review of the current literature, with the strongest focus on weight reduction for those who are overweight or obese.
"People with psoriatic disease tend to be overweight and to have metabolic syndrome, a complex disorder that also includes hypertension, diabetes, and premature arteriosclerosis," one of the authors of the paper, Sergio Schwartzman, MD, of Weill Cornell Medical College and the Hospital for Special Surgery in New York City, told MedPage Today. "A major recommendation is that in patients who are overweight and have metabolic syndrome, a strategy should be implemented that utilizes a hypocaloric diet to achieve weight reduction and ideal body weight."
This strong recommendation (i.e., strength 1) is based on level A evidence, with consistent results among the included studies evaluated and agreement with systematic reviews and meta-analysis, he and his colleagues wrote in the document, which is online in JAMA Dermatology.
An additional important message, Schwartzman said, is that dietary interventions "should be used not instead of, but in conjunction with, standard medical treatment for psoriatic disease."
The team searched the literature through 2017, identifying 55 interventional or observational studies, which included a total 4,534 patients with psoriatic disease.
Among the questions examined was whether or not a gluten-free diet could be beneficial.
Patients with psoriasis have a twofold increased frequency of celiac disease, and more often have the serologic markers of IgG tissue transglutaminase and IgA endomysial antibodies. In addition, high levels of these antibodies have been shown to correlate with worse skin disease.
Consequently, many psoriatic patients have tried gluten-free diets as a means of ameliorating their skin symptoms. However, the researchers recommended the use of gluten-free diets only for patients with confirmed celiac disease or those who are serologically positive, since no evidence could be found in the literature to support the use of gluten-free diets in patients negative for the serologic markers.
The investigators also examined the evidence for dietary supplements, which are commonly used by patients with psoriatic disease.
One popular supplement was fish oil, but studies have found conflicting results, the team said. In nine blinded clinical trials, seven found a lack of efficacy for fish oil in reducing disease severity, although broad differences were observed in the duration of use and daily dosages.
"We do not recommend oral fish oil supplementation for treatment of psoriasis in adults, because oral fish oil was not effective at the examined doses and durations," the authors wrote.
For vitamin D, uncontrolled data suggested that supplements used for 6 months or longer could be beneficial for plaque or erythrodermic psoriasis, but controlled studies found no benefit, so vitamin D was not recommended for disease prevention or treatment in patients with normal levels of the vitamin.
Selenium is an essential nutrient with immune system effects, and patients with psoriasis can have deficient levels. A small study of patients with erythrodermic psoriasis suggested that selenium supplementation along with coenzyme Q10 and vitamin E appeared beneficial when given along with conventional therapy, but the researchers concluded that the evidence was insufficient to recommend selenium supplementation for psoriasis.
The literature also indicated that vitamin B12 appeared to be ineffective, and supplementation was not recommended.
One small study suggested potential benefits for combination micronutrient supplements that included multiple vitamins and minerals, along with methotrexate, but the evidence was insufficient for a recommendation to be made.
For patients with psoriatic arthritis -- up to one-third of all patients with psoriasis -- the authors again strongly recommended weight reduction in patients whose body-mass index was 25 kg/m2 or greater. "Specifically, patients starting treatment with tumor necrosis factor blockers -- etanercept (Enbrel), adalimumab (Humira), or infliximab (Remicade) -- are significantly more likely to achieve minimal arthritis disease activity and to experience weight loss after a 6-month hypocaloric diet than after a regular diet," the authors noted.
They also recommended a trial of oral vitamin D supplementation in conjunction with standard therapy in patients with psoriatic arthritis, because uncontrolled studies found that 0.5 µg alfacalcidol or 0.5-2 µg calcitriol daily for 6 months significantly improved arthritic symptoms.
Limitations of the analysis, the researchers said, included the fact that some studies were not randomized or blinded, and that there was heterogeneity in the population studies, interventions, and outcomes measured.
The authors reported financial relationships with multiple companies, including AbbVie, Amgen, Celgene, Eli Lilly, Janssen Biotech, LEO Pharma, Novartis, Mallinckrodt, Pfizer, Valeant, Merck, UCB, Bristol-Myers Squibb, Incyte, Allergan, Boeheringer Ingelheim, Medimmune/AstraZeneca, and Genentech.