Higher Dietary Intake of Vitamin D Is Associated with Lower Incidence of Diabetic Nephropathy in Japanese Patients with Type 2 Diabetes

Abstract

Evidence for optimal dietary intake of vitamin D for prevention of diabetic complications is sparse although associations between low vitamin D intake and high incidence of diabetes and vitamin D supplementation and improvement in insulin resistance were reported. We aimed to investigate the relationship between vitamin D intake and the incidence of diabetes complications in Japanese patients with type 2 diabetes aged 40-70 years with HbA1c≥6.5%. The present analysis was conducted as a multicenter prospective study on the incidence of and risk factors for macro- and microvascular complications among 22Japanese patients with type 2 diabetes from outpatient clinics in 59 university and general hospitals in Japan.Analyzed were 1516 responders to a baseline dietary survey assessed by the Food Frequency Questionnaire based on food groups. Primary outcome was the 8-year risk of nephropathy, retinopathy, and cardiovascular disease (CVD). Cox regression analyses estimated hazard ratios (HRs) for dietary intake adjusted for age, gender, body mass index, HbA1c, smoking, energy intake, and other confounders. Mean vitamin D intake in quartiles ranged from 5.4 to 18.7μg/day. After adjusting for confounders, HRs of diabetic nephropathy in the 2nd, 3rd, and 4th quartiles for vitamin D intake compared with the 1st quartile were 0.7 (95% confidence interval 0.4-1.3, p=0.29), 1.2 (0.6-2.2, p=0.61), and 0.33 (0.14-0.79, p=0.01), respectively. There was no significant associations of vitamin D intake with retinopathy and CVD in the 2nd to 4th quartiles relative to the first quartile (retinopathy: 1.2 (0.9-1.6, 0.4), 0.8 (0.5-1.2, p=0.23), and 0.7 (0.5-1.0, p=0.08); CVD: 1.1 (0.7-1.7, p=0.83), 1.2 (0.7-2.0, p=0.62), and 0.7 (0.4-1.3, p=0.22)). Findings suggested that high vitamin D intake was associated with a lower incidence of diabetes nephropathy among Japanese patients with type 2 diabetes. Disclosure C. Horikawa: None. R. Aida: None. S. Tanaka: None. S. Tanaka: None. C. Kamada: None. Y. Yoshimura: None. A. Araki: None. T. Moriya: None. S. Katayama: None. H. Sone: Research Support; Self; Novo Nordisk Inc., Eli Lilly and Company, MSD K.K., Chugai Pharmaceutical Co., Ltd., Taisho Pharmaceutical Co., Ltd., Takeda Development Center Asia, Pte. Ltd., Daiichi Sankyo Company, Limited, Ono Pharmaceutical Co., Ltd., Kyowa Hakko Kirin Co., Ltd., Sanofi, Kowa Pharmaceuticals America, Inc., Eisai Inc..