Higher vitamin D levels associated with reduced risk of macular degeneration among women.

The results of a study reported in the April, 2011 issue of the American Medical Association journal Archives of Ophthalmology suggest that having a high level of vitamin D could be protective against the development of early age-related macular degeneration (AMD), a leading cause of vision loss in adults.

The Study involved 1,313 women participants in the Carotenoids in Age-Related Eye Disease Study (CAREDS), an ancillary study within the Women’s Health Initiative. Serum samples drawn between 1994 and 1998 were analyzed for 25-hydroxyvitamin D, which reflects vitamin D exposure from oral sources and sunlight. Dietary questionnaires administered upon enrollment were analyzed for vitamin D intake from food and supplements.

Although no significant association was found between vitamin D and early macular degeneration risk in the entire group, when subjects younger than 75 years of age were analyzed, a protective association emerged. “In women younger than 75, those who had 25-hydroxyvitamin D concentrations lower than 38 nanomoles per liter were more likely to have age-related macular degeneration than women with concentrations greater than 38 nanomoles per liter,” reported University of Buffalo School of Public Health and Health Professions assistant professor Amy E. Millen, PhD, who is the article’s lead author. “Blood concentrations above 38 nanomoles per liter were associated with at least a 44 percent decreased odds of having AMD.”

Intake of vitamin D from food and supplements was also found to be protective against early disease in participants under the age of 75. Those whose intake was among the top one-fifth of participants experienced a 59 percent lower risk of developing AMD compared to women whose intake was among the lowest fifth. Time spent in direct sunlight did not appear to be protective against the disease.

“The take-home message from this study is that having very low vitamin D status (25-hydroxyvitamin D blood concentrations lower than 38 nanomoles per liter) may be associated with increasing your odds of developing age-related macular degeneration,” Dr Millen concluded. “But based on these study findings, being at a higher vitamin D level than 38 nanomoles per liter does not appear to be more protective.”

“This is a promising study, but more still needs to be done,” she added. “We still don’t understand all of the effects of vitamin D on health.”