Long-term dietary vitamin D intake and risk of fracture and osteoporosis: a longitudinal cohort study of Swedish middle-aged and elderly women.

Abstract

The importance of dietary vitamin D for osteoporotic fracture prevention is uncertain. Our objective was to investigate associations between dietary vitamin D intake with risk of fracture and osteoporosis. In the population-based Swedish Mammography Cohort (including 61 433 women followed for 19 years), diet was assessed by repeated food frequency questionnaires. The study was conducted in 2 municipalities in central Sweden. Incident fractures were identified from registry data. In a subcohort (n = 5022), bone mineral density was determined by dual-energy x-ray absorptiometry and serum 25-hydroxyvitamin D was measured using HPLC-tandem mass spectrometry. A total of 14 738 women experienced any type of first fracture during follow-up, and 3871 had a hip fracture. Multivariable-adjusted hazard ratio (HR) for any first fracture was 0.96 (95% confidence interval, 0.92-1.01) for the lowest (mean, 3.1 μg/d) and 1.02 (0.96-1.07) for the highest (mean, 6.9 μg/d) quintile compared with the third quintile of vitamin D intake. The corresponding HR for a first hip fracture was 1.02 (0.96-1.08) for the lowest and 1.14 (1.03-1.26) for the highest quintile. Intakes >10 μg/d, compared with <5 μg/d, conferred an HR of 1.02 (0.92-1.13) for any fracture and an HR of 1.27 (1.03-1.57) for hip fracture. The intake of vitamin D did not affect the odds for osteoporosis, although higher levels were associated with higher bone mineral density (0.3%-2%, P < .0001). A positive association was observed between vitamin D intake and serum 25-hydroxyvitamin D. Dietary intakes of vitamin D seem of minor importance for the occurrence of fractures and osteoporosis in community-dwelling Swedish women.