Clinical Question

Does vitamin D supplementation in women with low levels of the vitamin affect bone mineral density, muscle mass, strength, or fall risk?

Bottom Line

You do not have to treat a low vitamin D level if your patient is a typical community-dwelling postmenopausal woman younger than 75 years. The usual dosage of vitamin D, 800 IU (20 mcg) daily, will not increase levels even after a year of therapy and has little effect on calcium absorption or bone mineral density. A high dosage, 50,000 IU (125 mcg) twice monthly, will raise levels but is similarly ineffective in improving minimally low bone mineral density, muscle strength, functional status, physical activity levels, or risk of falls. Not checking vitamin D levels will make it easier not to (ineffectively) treat low levels. (Level of Evidence = 1b)

Synopsis

These investigators, through community advertising, enrolled a total of 230 postmenopausal women, 90% of whom were white, with an average age of 61 years and baseline vitamin D levels of 14 to 27 ng per mL (35 to 67 nmol per L). A low 25-hydroxyvitamin D level is typically less than 30 ng per mL (75 nmol per L). The women had low-normal hip T-scores of bone mineral density (average: −1 standard deviation). Using typical tests of balance and lower extremity strength, the women were at low risk of falls. The women were randomized, using concealed allocation, to receive placebo, daily vitamin D₃ at 800 IU (20 mcg), or twice-monthly vitamin D₃ at 50,000 IU (125 mcg). The twice-monthly, high-dosage group had their vitamin D levels monitored, and the dosage was increased if levels did not increase to at least 30 ng per mL.

After one year, neither vitamin D treatment regimen changed bone mineral density, muscle mass, functional status, or physical activity levels. The number of women reporting at least one fall—almost one-half of the women—was not different among the groups. The study was only one year in length, which should be long enough to see changes in vitamin D levels and muscle mass, although perhaps not long enough to see changes in fall rates (if there is a difference). The U.S. Preventive Services Task Force concludes there is insufficient evidence to recommend for or against screening for vitamin D deficiency; the National Institute for Health and Care Excellence recommends vitamin D supplementation in members of high-risk groups.

Study design: Randomized controlled trials

Funding source: Government

Allocation: Concealed

Setting: Outpatient (any)

Reference: HansenKEJohnsonREChambersKRet alTreatment of vitamin D insufficiency in postmenopausal women: a randomized clinical trial. JAMA Intern Med2015; 175( 10): 1612– 1621.