Prevention of bone loss by vitamin D supplementation in elderly women: A randomized double-blind trial

The purpose of the study was to determine the effect of vitamin D supplementation on bone turnover and bone loss in elderly women. Three hundred forty-eight women, ages 70 yr and older, were randomized to receive 400 IU vitamin D₃ per day (n = 177) or placebo (n = 171), double-blind, for a period of 2 yr. Main outcome measures were bone mineral density of both hips (femoral neck and trochanter) and the distal radius, as well as biochemical markers of bone turnover. The effect of vitamin D supplementation was expressed as the difference in mean (percentage) change between the placebo group and the vitamin D group. The measurements were repeated in 283 women after 1 yr and in 248 women after 2 yr. Vitamin D supplementation significantly increased serum 25-hydroxyvitamin D (250HD) (+35 nmol/L) and 1,25-dehydroxyvitamin D [1,25-(OH)₂D] (+7.0 pmol/L) levels and urinary calcium/creatinine ratios (+0.5%) and significantly decreased PTH(1-84) secretion (-0.74 pmol/L) after 1 yr. No effect was found for the parameters of bone turnover. The effect on the bone mineral density of the left femoral neck was +1.8% in the first yr, +0.2% in the second yr, and +1.9% during the whole period (95% confidence interval 0.4, 3.4%). At the right femoral neck the effects were +1.5%, +1.1%, and +2.6% (confidence interval 1.1, 4.0%), respectively. No effect was found at the femoral trochanter and the distal radius. Supplementation with 400 IU vitamin D₃ daily in elderly women slightly decreases PTH secretion and increases bone mineral density at the femoral neck.