Optimizing Postmenopausal Vitamin D₃ Supplementation

Vitamin D deficiency is defined as a serum 25-hydroxyvitamin D (25[OH]D) level of <20 ng/mL (<50 nmol/L), and vitamin D insufficiency is defined as <30 ng/mL (<72.5 nmol/L; JW Gen Med Jun 23 2011). Although insuffiency is diagnosed frequently, no clear guidelines exist for determining the optimal replacement dose. In this randomized placebo-controlled trial, 163 healthy postmenopausal white women (mean body-mass index, 30 kg/m²) with vitamin D insufficiency (mean baseline 25[OH]D level, 16 ng/mL [39 nmol/L]) were assigned to receive placebo or various doses of daily vitamin D₃ supplementation (ranging from 400–4800 IU). Participants were followed for 1 year.

Daily doses of 800 IU increased 25(OH)D levels to >20 ng/mL in 97.5% of women. Altho…