Evidence for optimal dietary intake of calcium for prevention of diabetic complications is sparse although population-based cohort studies showed that calcium intake reduces the risk of type 2 diabetes (T2D). We aimed to investigate the relationship between calcium intake and the incidence of diabetes complications in Japanese patients with T2D aged 40-70 years with HbA1c ≥6.5%. This analysis was conducted as a multicenter prospective study of the incidence of and risk factors for macro- and microvascular complications among 2205 Japanese patients with T2D from outpatient clinics in 59 university and general hospitals in Japan. Analyzed were 1588 responders to a baseline dietary survey assessed by the Food Frequency Questionnaire based on food groups or a dietary record. 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, BMI, HbA1c, smoking, energy intake, and other confounders. Mean calcium intake in quartiles ranged from 487.5 to 751 mg/day, and more than half of participants had calcium intake below the recommended daily dietary allowance in Japan (men 700 mg/d; women 650 mg/d). After adjusting for confounders, HRs of diabetic nephropathy in the 2nd, 3rd, and 4th quartiles for calcium intake compared with the 1st quartile were 1.20 (95% confidence interval 0.67-2.18, p=0.540), 0.60 (0.28-1.28, p=0.185), and 0.42 (0.18-0.97, p=0.024), respectively. There were no significant associations of calcium intake with retinopathy and CVD in the 2nd to 4th quartiles relative to the 1st quartile (retinopathy: 1.15 (0.81-1.64, p=0.441), 1.14 (0.78-1.68, p=0.491), and 0.93 (0.59-1.46, p=0.809); CVD: 0.86 (0.51-1.44, p=0.558), 0.92 (0.53-1.61, p=0.763), and 0.81 (0.42-1.53, p=0.508). Findings suggested an association of high calcium intake with a lower incidence of diabetes nephropathy in Japanese patients with T2D.
C. Horikawa: None. R. Aida: None. S. Tanaka: None. S. Tanaka: None. C. Kamada: None. Y. Yoshimura: None. A. Araki: Speaker's Bureau; Self; Dainippon Sumitomo Parma Co. Ltd., Merck & Co., Inc., Tanabe Mitsubishi Pharma Corporation. T. Moriya: None. S. Katayama: None. Y. Akanuma: None. H. Sone: Research Support; Self; Astellas Pharma Inc., Boehringer Ingelheim Pharmaceuticals, Inc., Daiichi Sankyo Company, Limited, Kowa Pharmaceutical Europe Co. Ltd., Kyowa Hakko Kirin Co., Ltd., Novo Nordisk Inc., Ono Pharmaceutical Co., Ltd., Taisho Pharmaceutical Co., Ltd., Takeda Pharmaceutical Company Limited, Teijin Pharma Limited.
Japan Society for the Promotion of Science; Japan Ministry of Health, Labour and Welfare