Urinary calcium and renal function in the Japanese female population

The Japanese have not reached the recommended daily allowance (RDA) for calcium (Ca, 600 mg/day), they are a Ca-deficient population. To determine factors influencing urinary Ca (U-Ca) in the Ca-deficient female population, age, body mass index (BMI), drinking habits, smoking habits and Ca intake were surveyed, and urinary albumin (U-Alb) and retinol binding protein (U-RBP) as renal function tests were analyzed in 210 Japanese females aged 24-76 years. The mean Ca intake for the subjects was 542.8 mg/day, which was less than the RDA for Ca. A significant positive correlation was found between U-RBP and U-Ca, but neither age, BMI, drinking habits, smoking habits, Ca intake nor U-Alb would affect U-Ca in the subjects. In a Ca-deficient status, a proximal tubular dysfunction may be a significant factor increasing Ca loss in urine, and may be a risk factor for osteoporosis.