Dietary habits in Japanese patients with psoriasis and psoriatic arthritis: Low intake of meat in psoriasis and high intake of vitamin A in psoriatic arthritis

Psoriasis is characterized by T‐helper 17 cell‐dominant abnormal immunity, and hyperproliferation and abnormal differentiation of epidermal keratinocytes. Some patients are associated with arthritis. Dietary habits can modulate the pathogenesis of psoriasis. Previous studies in Western countries showed higher body mass indices, higher intake of fat and lower intake of fish or vegetables in psoriatic patients compared with the reference groups. We evaluated dietary habits in adult Japanese psoriatic patients, using a validated brief‐type self‐administered dietary history questionnaire, and compared the results to those of age‐ and sex‐matched healthy controls. The results in psoriatic patients with arthritis were compared with those in the patients without. Japanese psoriatic patients showed higher body mass indices, higher intake of fish/shellfish, pulses, sugar/sweeteners, vitamin B₁₂ and vitamin D, and lower intake of meat, compared with those of healthy controls. The logistic regression analysis showed that psoriasis was associated with high body mass index and low intake of meat. The intake of confection in patients with high Psoriasis Area and Severity Index was higher than that in those with low index. The intake of β‐carotene, vitamin A and green/yellow vegetables in psoriatic patients with arthritis were higher than those in the patients without. The dietary habits in Japanese psoriatic patients are rather different from those in Western patients. This is the first study showing the differences in dietary habits between psoriatic patients with arthritis and those without. Further studies should elucidate the relationships of these results with skin and joint lesions in psoriatic patients.