Vitamin D supplements may be ineffective in improving bone density or bone strength in postmenopausal women, a clinical trial has found.
Researchers randomized 230 women to one of three groups: a low-dose group who took 800 units of vitamin D daily; a high-dose group who took 50,000 units twice a month; and a group that received placebo pills.
All had similar vitamin D blood levels at the start of the study, about 20 milligrams per deciliter. By the end of one year, the average vitamin D levels were 42 in the high-dose group, 27 in the low-dose group, and 18 in the placebo group.
Calcium absorption increased about 1 percent in the high-dose group, while decreasing 2 percent in the low-dose group and 1.3 percent in the placebo takers. But there was no difference among groups in changes in bone mineral density or trabecular bone score, a measure of osteoporosis risk. Nor was there any difference in the number of falls or the ability to exercise. The study is in JAMA Internal Medicine.
“Right now, our patients are getting mixed messages from ‘don’t bother taking D at all’ to ‘take 2,000 too 4,000 units a day,’ so what are we to do?” said the lead author, Dr. Karen E. Hansen, an associate professor of medicine at the University of Wisconsin. “This study supports a middle-of-the-road approach. If your D level is 20 or higher, that’s enough, and if you’re low, you can achieve that with 600 to 800 units a day.”