Serum 25(OH)D3 vitamin status of elderly Finnish women is suboptimal even after summer sunshine but is not associated with bone density or turnover

Abstract

Concentrations of 50 and 75 nmol/l are proposed as serum 25-hydroxyvitamin D (25(OH)D) target for older people from the view of bone health. We evaluated vitamin D status of elderly Finnish women in light of these definitions, its relationship to bone mineral density (BMD) and turnover, and improvement by summer sunshine. Population-based study. A total of 1604 ambulatory women aged 62-79 years were studied; 66% used vitamin D supplements. Serum 25(OH)D(3) was measured with HPLC before and after summer, and heel BMD in spring. In subgroups, serum parathyroid hormone (PTH) and type I procollagen aminoterminal propeptide (PINP) were analyzed. In spring, 60.3% of the women had 25(OH)D(3) <or=50 nmol/l, and the target of 75 nmol/l was reached by 9.1%. For supplement users, the respective numbers were 52.1 and 11.9%. Serum 25(OH)D(3) did not determine BMD or bone turnover measured by serum PINP. Summer sunshine increased serum 25(OH)D(3) by 17.4% (P<0.0001), but in autumn 84% of the subjects remained under the target of 75 nmol/l. In supplement users, PTH remained stable but decreased in others during summer (P=0.025). Vitamin D status of elderly Finnish women is suboptimal if 25(OH)D(3) levels of 50 or 75 nmol/l are used as a threshold. It is moderately increased by supplement intake and summer sunshine. However, 25(OH)D(3) concentrations did not influence bone density in terms of serum PINP and bone turnover rate.