Lack of Vitamin D Tied to Multiple Sclerosis
Vitamin D has already been linked to stronger bones and lower rates of diabetes, colon cancer, and prostate cancer. Now a new finding provides more evidence of the nutrient's disease-preventive powers.
In a study released in today's issue of the Journal of the American Medical Association, Harvard researchers found that those with the highest vitamin D blood levels had a 62 percent lower risk of developing multiple sclerosis (MS) than those with the lowest levels. About 350,000 Americans have the neurological disease in which immune cells attack the protective coating on nerve cells, causing progressive paralysis. Although the body can make all the vitamin D it needs from the sun's rays, most of us become deficient during the winter months when, in areas north of Atlanta, the sun doesn't get high enough in the sky for UV rays to penetrate the atmosphere.
Previous research found that those who lived in northern regions with less sunlight had higher rates of MS. And a 2004 study, also from Harvard, showed that those who took vitamin D supplements had a lower risk of the disease. Vitamin D is thought to modulate immune system to keep it from attacking healthy tissues and organs.
In the current study, researchers identified 257 U.S. soldiers diagnosed with MS and then analyzed their blood samples drawn when they had first entered active service years before the disease was diagnosed and held in a military storage bank. The researchers then compared these blood samples with samples from other healthy soldiers who were matched for their age, gender and ethnicity.
Among whites, the risk of the disease was lowest in those with the highest blood levels of vitamin D. The researchers, though, didn't find the same association among blacks and Hispanics, but also found that none of the individuals in these two groups had blood levels in the range of the highest levels found in whites. (African-Americans and dark-skinned individuals have much higher rates of vitamin D deficiency since their skin pigmentation blocks out the sun's radiation.)
"We also had small sample sizes for the minority groups, so it could be that our study was underpowered," explains study leader Kassandra Munger, a doctoral candidate in nutrition at Harvard School of Public Health in Boston.
Should people start taking vitamin D supplements to prevent MS?
"There's not enough evidence yet to recommend that," Munger says. Still, with all the research showing the importance of vitamin D for bone health and cancer prevention, she says, it's not a bad idea for everyone to be taking supplements. How much? Most experts now agree that the government's recommended intake, of 200 international units up to age 50, 400 IUs up to age 70, and 600 IUs over 70, isn't enough to get an optimal amount. Taking 1,000 to 2,000 IUs may be a better bet, she says.