THURSDAY, April 3, 2003 (HealthDayNews) --
Normal levels of vitamin D aren't enough to achieve optimal absorption of calcium.
That's the suggestion of two studies in the April issue of the Journal of the American College of Nutrition.
The Creighton University studies indicate that vitamin D supplements can increase calcium absorption by as much as 65 percent, even when a person's initial level of vitamin D is normal.
The studies, done a year apart, included 34 healthy, postmenopausal women in Omaha, Neb.
In one study, the women took 500 milligrams of calcium, but not vitamin D supplement. In the other study, the women took the same amount of calcium, but took vitamin D for three weeks before they started taking the calcium.
"The lower end of the normal range of blood vitamin D levels is clearly sub-optimal for calcium absorption. Our evidence points out that low, normal vitamin D status exaggerates the effects of low calcium intake," Dr. Robert P. Heaney, senior author of both studies, says in a news release.
The research indicates an increased need for vitamin D in the population. Current recommendations for vitamin D intake are 200 International Units (IU) daily for adults up to 50 years old, 400 IU for people aged 51 to 70, and 600 IU for people over age 70.
Vitamin D is made naturally in the skin when it's exposed to sunlight. But concerns about skin cancer mean many people limit the amount of time they spend in the sun. And there isn't enough sun during winter to stimulate vitamin D production in the skin of people living in the northern half of the United States.
More information
Here's where you can learn more about vitamin D.
