Dietary calcium and vitamin D intake in relation to osteoporotic fracture risk

The etiologic role of dietary calcium and vitamin D intake in primary prevention of osteoporotic fractures is uncertain, despite considerable research efforts. With the aim to examine these associations with an improved precision, we used data from a large population-based prospective cohort study in central Sweden. We estimated nutrient intake from a self-administered food-frequency questionnaire filled in by 60,689 women, aged 40-74 years at baseline during 1987-1990. During follow-up, we observed 3986 women with a fracture at any site and 1535 with a hip fracture. Rate ratio of fractures (RR) and 95% Cl were estimated using Cox proportional hazards models. We found no dose-response association between dietary calcium intake and fracture risk. The age-adjusted RR of hip fracture was 1.01 (95% CI 0.96-1.06) per 300 mg calcium/day and the corresponding risk of any osteoporotic fracture was 0.99 (95% CI 0.96-1.03). Furthermore, women with an estimated calcium intake below 400 mg/day and those with a calcium intake higher than 1200 mg/day both had a similar age-adjusted hip fracture risk as those with intermediate calcium intakes: RR 1.07 (95% Cl 0.92-1.24) and RR 1.00 (95% Cl 0.79-1.27), respectively. Vitamin D intake was not associated with fracture risk. Furthermore, women in the highest quintiles compared to the lowest quintiles of both calcium and vitamin D intake had an age-adjusted RR of 1.02 for all fractures (95% Cl 0.88-1.17). Dietary calcium or vitamin D intakes estimated at middle and older age do not seem to be of major importance for the primary prevention of osteoporotic fractures in women. (C) 2003 Elsevier Science (USA). All rights reserved.