High-dose vitamin D supplements slightly increase calcium absorption but do not improve bone density, muscle function and mass or fall rates in postmenopausal women, new research has shown.

“We found no data to support experts’ recommendations to maintain serum 25-hydroxyvitamin (OH)D level of 30 ng/mL or higher in postmenopausal women,” said lead author Dr. Karen E. Hansen from the University of Wisconsin School of Medicine and Public Health, Wisconsin, US and colleagues.

The researchers examined the impact of vitamin D supplementation on 230 women who were 5 years past menopause (age 75 years or younger) with 25(OH)D levels of 14 through 27 ng/mL at study entry. Women were randomized to low-dose or high-dose cholecalciferol or placebo. [JAMA Intern Med 2015;doi:10.1001/jamainternmed.2015.3874]

At 1 year of treatment, mean 25 (OH) levels increased in the low-dose and high-dose group (28 and 56 ng/mL, respectively) but decreased in the placebo group (19 ng/mL). Fractional excretion of calcium was slightly better with high-dose cholecalciferol compared with low-dose cholecalciferol or placebo, but these differences are not clinically significant.

Neither dose of cholecalciferol improved bone mineral density or muscle outcomes (function, strength, mass) or the number of falls among the three groups.

Although it is possible that treatment for over a year may result in better outcomes, the findings suggest that vitamin D supplementation may be no better than placebo, said Dr. Deborah Grady from the University of California, San Francisco, US, in an accompanying editorial. “The data provide no support for use of higher-dose cholecalciferol replacement therapy or any dose of cholecalciferol compared with placebo.” [JAMA Intern Med2015; doi:10.1001/jamainternmed.2015.3937]

The low-dose regimen consisted of 800 IU vitamin D daily, and the high-dose regimen 50,000 IU twice monthly administered after a 15-day loading dose. Women in the high-dose group received extra doses as needed to keep their serum 25(OH)D level above 30 ng/mL.