The Effect of Vitamin D Supplementation on Vitamin D Status and Parathyroid Function in Elderly Subjects*

Abstract

Vitamin D deficiency is common in the elderly and may lead to secondary hyperparathyroidism, cortical bone loss, and hip fractures. The effect of vitamin D supplementation for 1 yr was studied in 72 people living in a nursing home and 70 people living in an aged people’s home. The subjects were randomized into 3 groups: control, and 400 or 800 IU vitamin D₃/day. The initial vitamin D status of each subject was classified as deficient or borderline [serum 25-hydroxyvitamin D (25OHD) 2D] concentrations increased slightly but significantly, and the increase was inversely related to the initial serum 25OHD concentration. Serum intact PTH-(1–84) concentrations decreased about 15% during supplementation in both nursing home and aged people’s home residents, whereas serum osteocalcin significantly decreased in the nursing home residents only. We conclude that a vitamin D₃ supplement of 400 IU/day adequately improves vitamin D status in elderly people and increases 1,25-(OH)₂D concentrations in those with vitamin D deficiency. Supplementation decreases parathyroid function and may depress bone turnover to some degree.