Many Americans Fall Short on Their Vitamin D

The researchers found that vitamin D supplements decreased the risk of non-vertebral fractures by 14 percent and of hip fractures by 9 percent. In trials where people were given doses of more than 400 IUs a day, fractures were reduced by 20 percent and hip fractures by 18 percent.

In addition, for people taking high doses of vitamin D, calcium supplements did not appear to have any additional protective effect against fractures, the researchers reported.

"At the higher dose, this benefit is not restricted to frail older individuals, but is also present in community-dwelling older individuals," Bischoff-Ferrari said. "In the subgroup of community-dwelling older individuals, vitamin D at the higher dose reduced non-vertebral fractures by 33 percent."

Dr. Michael F. Holick, director of the Vitamin D Laboratory at Boston University, noted that the recommended levels of vitamin D are under review and likely to be increased.

"An Institute of Medicine panel is planning to have new recommendations out by mid-2010," Holick said. "It's pretty clear that you need a minimum of 1,400 and up to 2,000 IU a day, and if you are obese, you probably need at least one and a half to two times as much, because the fat sequesters the vitamin D," he said.

Holick said people are drinking less milk and staying out of the sun, which are the main reasons for the decreasing vitamin D levels in the population.

One way to combat the problem is to increase vitamin D supplementation in foods, Holick said. New recommendations that increase vitamin D levels will let the food industry increase vitamin D levels in foods and add vitamin D to more foods, he said.

"We are in desperate need to have a marked increase in the adequate intake recommendation, and hopefully, that will be 1,000 to 2,000 IUs per day and raise the safe upper limit to at least 10,000 IUs a day," Holick said. "The plan would be to increase the amount per serving and increase the number of foods fortified with vitamin D."

More information

For more on vitamin D, visit the U.S. National Library of Medicine.