During the winter months, most people have lower than usual levels of vitamin D because of their reduced exposure to sunlight.
Sometimes called the “sunshine vitamin,” vitamin D is active in tissues and cells throughout the body, and is believed to help prevent or reduce a wide range of diseases. But researchers aren’t exactly sure what roles vitamin D plays, and judging how much vitamin D is enough—and for whom—remains something of a moving target.
In a recent double-blind study among NASCAR pit crew atheletes, published in the December 2013 issue of the journal Nutrients, researchers from Appalachian State University (ASU) found that taking vitamin D2 supplements decreased levels of vitamin D3 in the body, and resulted in greater muscle damage after intense weight lifting.
“When the sun hits our skin, it turns into vitamin D3; the body is used to that,” said study director David Neiman, DrPH, professor of health, leisure, and exercise science, and director of the ASU human performance laboratory. “High vitamin D2 levels are not a normal experience for the human body. Taking high doses of vitamin D2 caused something to happen at the muscle level that isn’t in the best interest of the atheletes.
“While vitamin D2 levels in the blood increased, we found that levels of the valuable D3 decreased,” Nieman added. “And to our surprise, those taking vitamin D2 didn’t have just a little more muscle damage, they had a lot more damage.”
Many researchers are nevertheless certain that some level of vitamin D offers protective health benefits. In a JAMA Neurology study published online at the end of January, researchers from the Harvard School of Public Health found that high serum concentrations of 25-hydroxyvitamin D (25[OH]D) may be associated with reduced disease activity and a lower risk of disease progression among people with multiple sclerosis.
“Among patients with MS mainly treated with interferon beta-1b, low 25(OH)D levels early in the disease course are a strong risk factor for long-term MS activity and progression,” wrote the authors.
Specifically, the team found that increases of 50 nmol/L in average blood 25(OH)D levels within the first 12 months of observation appeared to be associated with 57% lower risk of new active brain lesions, 57% lower risk of relapse, 25% lower yearly increase in T2 lesion volume, and 0.41% lower yearly loss in brain volume from months 12 to 60 of the follow-up period.
As indicated in this issue’s feature story on vitamin D testing (page 16), much research remains to be done to understand the health benefits of vitamin D. Along the way, test manufacturers and laboratorians will play important roles in improving the tools and practices needed to conduct the research and turn its results into meaningful practices that improve patient care.
Steve Halasey
Chief Editor, CLP
[email protected]
(626) 219-0199
