Research appearing in the November 2007 issue of the American Journal of Clinical Nutrition looked at vitamin D levels and aging. Specifically, the researchers measured telomeres in 2,160 women between the ages of 18 and 79, and measured vitamin D levels. Telomeres are part of a chromosome; they tend to shorten with age.  Longer telomeres are associated with slower aging.  The study found that women with higher levels of vitamin D tended to have longer telomeres. They may age more slowly than people with low vitamin D levels.