Diet and systemic lupus erythematosus: a 4 year prospective study of Japanese patients.

Objective: To investigate the associations of dietary factors with the occurrences of active disease and vascular damage in female patients with systemic lupus erythematosus (SLE).

Methods: Clinical and questionnaire data were collected from 279 female patients with SLE in a 1995 baseline survey. Dietary nutrients were estimated by a semiquantitative food frequency questionnaire and disease activity was evaluated based on the Lupus Activity Criteria Count. Patients were followed over 4 years (1995-99) and changes in disease activity and occurrences of major organ damage were determined. Using data from 216 patients with inactive disease whose dietary data were complete at baseline, the association of each nutrient intake with occurrence of active disease was evaluated. The relation of diet with the development of 3 types of vascular injury (ischemic heart disease, cerebrovascular accident, thrombotic events) was examined in 196 patients who had been inactive with no history of these injuries. Patients who developed these vascular events were put in one category and nutrient intakes at baseline were compared between patients who did or did not develop vascular events.

Results: A total of 9966 person-months were accumulated from the 216 inactive patients, among whom 43 patients developed active disease. The proportional hazard model including indicator variables for tertiles of each nutrient, total energy, and confounding variables revealed an inverse association of intake of vitamin C (p for trend = 0.005) and crude fiber (p for trend = 0.06) with the risk of active disease. The inverse association with vitamin C intake was also significant after Bonferroni adjustment. Patients who developed vascular events (n = 7) consumed a greater amount of vegetable fat at baseline than patients who did not (p = 0.04).

Conclusion: Our findings suggest that dietary nutrients may modify clinical course of disease in female patients with SLE. Vitamin C intake is inversely associated with the risk of active disease, suggesting that vitamin C intake may prevent the occurrence of active SLE disease.