Effect of dietary B vitamins on BMD and risk of fracture in elderly men and women: the Rotterdam study

Abstract

A mildly elevated homocysteine (Hcy) level is a novel and potentially modifiable risk factor for age-related osteoporotic fractures. Elevated Hcy levels can have a nutritional cause, such as inadequate intake of folate, riboflavin, pyridoxine or cobalamin, which serve as cofactors or substrates for the enzymes involved in the Hcy metabolism. We examined the association between intake of Hcy-related B vitamin (riboflavin, pyridoxine, folate and cobalamin) and femoral neck bone mineral density BMD (FN-BMD) and the risk of fracture in a large population-based cohort of elderly Caucasians. We studied 5304 individuals aged 55 years and over from the Rotterdam Study. Dietary intake of nutrients was obtained from food frequency questionnaires. Incident non-vertebral fractures were recorded during a mean follow-up period of 7.4 years, and vertebral fractures were assessed by X-rays during a mean follow-up period of 6.4 years. We observed a small but significant positive association between dietary pyridoxine (beta = 0.09, p = 1 x 10(-8)) and riboflavin intake (beta = 0.06, p = 0.002) and baseline FN-BMD. In addition, after controlling for gender, age and BMI, pyridoxine intake was inversely correlated to fracture risk. As compared to the three lowest quartiles, individuals in the highest quartile of age- and energy-adjusted dietary pyridoxine intake had a decreased risk of non-vertebral fractures (HR = 0.77, 95% CI = 0.65-0.92, p = 0.005) and of fragility fractures (HR = 0.55, 95% CI = 0.40-0.77, p = 0.0004). Further adjustments for other dietary B vitamins (riboflavin, folate and cobalamin), dietary intake of calcium, vitamin D, vitamin A and vitamin K, protein and energy intake, smoking and BMD did not essentially modify these results. We conclude that increased dietary riboflavin and pyridoxine intake was associated with higher FN-BMD. Furthermore, we found a reduction in risk of fracture in relation to dietary pyridoxine intake independent of BMD. These findings highlight the importance of considering nutritional factors in epidemiological studies of osteoporosis and fractures.