High Doses of Vitamin D3 Are Not Superior to Standard Dose in Post-menopausal Women

Written by Julie M. Gentile
Reviewed by EndocrineWeb Editorial Board

Although vitamin D is commonly used among patients with osteoporosis, the optimal dose has not yet been determined.

Research from Norway examined whether a high dose of vitamin D3 is better than the standard dose in boosting bone mineral density (BMD) and decreasing bone turnover in post-menopausal women with low bone mass.

Results were published online in September 2011 (soon to be published in Osteoporosis International) in an article called “The effect of high-dose vitamin D on bone mineral density and bone turnover markers in post-menopausal women with low bone mass-a randomized controlled 1-year trial.”

This 1-year randomized double-blind controlled trial included 297 women (50 to 80 years old). Postmenopausal women (n=297) with a BMD T-score of ≤ -2.0 in the lumbar spine (L2-L4) or total hip were included. They were randomized to 6,500 IU vitamin D3/day (20,000 IU 2 times/week + 800 IU/day) or 800 IU vitamin D3/day (placebo 2 times/week + 800 IU/day). Both groups also took 1,000 mg of elemental calcium/day; the primary endpoint was a change in BMD in the lumbar spine (L2-L4) and total hip.

The study found that after 1 year, serum 25-hydroxyvitamin D (25(OH)D) increased (mean [SD]) from 71 (23) to 185 (34) nmol/l and from 71 (22) to 89 (17) nmol/l in the high- and standard-dose vitamin D3 groups, respectively.

Furthermore, BMD for all measurement sites was either unchanged or had slightly improved with no significant differences between the 2 groups. Bone turnover decreased in both groups, but the more significant reduction in serum levels of bone formation marker P1NP in the standard-dose group possibly indicates that it was more effective. It was also noted that adverse events did not differ between the 2 groups.

Researchers concluded that after 1 year, treatment with 6,500 IU vitamin D3/day was not superior to the standard dose of 800 IU/day in improving BMD in the spine and hip in vitamin D-replete post-menopausal women who had decreased bone mass and was less efficient in reducing bone turnover.

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