Vitamin D fails to benefit blacks

Vitamin D supplementation does not appear to have the same bone-strengthening benefits in post-menopausal black women as it does in older white women, according to a study in yesterday’s issue of Archives of Internal Medicine.

“To our knowledge, this study is the first clinical trial examining the effect of vitamin D on bone loss in African-American women,” bone specialists at Winthrop University Hospital in Mineola, N.Y., wrote.

“Our study demonstrated a lack of benefit of vitamin D supplementation in loss of skeletal mass in calcium-sufficient African-American women in midlife.”

Dr. John F. Aloia, chief academic officer at Winthrop and the report’s first author, said he and his colleagues had assumed that giving black post-menopausal women substantially more vitamin D than is recommended would decrease bone loss in that population. In fact, he said, many scientists hypothesized it would have this effect.

The authors said previous trials that “suggest a benefit of vitamin D supplementation have been conducted with white participants.”

“But our study found that giving post-menopausal African-American women much more vitamin D is not beneficial” in preserving bone-mineral density, Dr. Aloia said.

Researchers said further studies are needed to determine if their findings are applicable to women of other ethnic groups.

The study in Archives examined 280 healthy black women, ages 50 to 75, who, daily over a three-year period, received either a placebo or a large supplemental dose of vitamin D. Neither investigators nor study participants knew who received what.

Dr. Aloia stressed that every woman in the experiment, whether she was part of the test group or control group, received calcium supplements to ensure a calcium intake of between 1,200 and 1,500 milligrams daily.

The authors said there is “general agreement” that this is the “optimal calcium intake recommended for reducing post-menopausal bone loss.”

They said it is also widely recognized that vitamin D is important in calcium maintenance. However, there has been uncertainty and conflict as to the optimal intake of vitamin D, the researchers said in background information.

Dr. Aloia said it is recommended that women between the ages of 50 and 70 take 400 international units of vitamin D per day. Those over 70 are advised to take 600 international units daily.

He added that he is not recommending that post-menopausal black women stop taking vitamin D supplements.

“The study showed a transient improvement in bone density” in the first year, but not the full three years of the experiment, he said. In addition, he said, there was no evidence that even high doses of vitamin D supplements are harmful.