Could Vitamin D Protect Against Macular Degeneration?
In addition to keeping brittle bones at bay, vitamin D may help to protect against age-related macular degeneration (AMD), according to a recent study in JAMA Ophthalmology online.
Researchers found that women deficient in vitamin D with a specific high-risk genotype for AMD are nearly 7 times more likely to develop the debilitating eye disease than those with adequate vitamin D without the high-risk genotype.
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“Our study’s findings suggest that being deficient for vitamin D may increase one’s risk for AMD—and that this increased risk may be greatest in those with the highest genetic risk for a specific variant in a protein called complement factor H (CFH),” says lead study author Amy Millen, PhD, associate professor of epidemiology and environmental health in the School of Public Health and Health Professions at the University at Buffalo.
Among many genes linked to AMD, one of the strongest is Y402H—a specific variant in the CFH gene. This gene codes for the CFH protein involved in the body’s immune response to eliminate bacteria and viruses.
“Inflammation is thought to be involved in the pathogenesis of AMD,” Millen explains. “We had hypothesized that vitamin D would protect against AMD because of its anti-inflammatory and immune-modulating properties.”
Millen and her colleagues studied the relationship between vitamin D status and AMD by analyzing data from 913 women, ages 54 to 74, who participated in the Carotenoids in Age-related Eye Disease Study. They measured the levels of 25-hydroxyvitamin D, a vitamin D biomarker, in the patients’ serum samples to determine their vitamin D status.
Of the participants, 550 had adequate levels of vitamin D; 275 had inadequate levels; and 88 showed deficient levels. Investigators observed a 6.7-fold increased odds of AMD among women with vitamin D status < 12 ng/ml who possessed 2 risk alleles for CFH Y402H.
“If a woman is at increased risk for AMD due to her genetics, maintaining an adequate vitamin D status may help reduce her risk,” Millen says.
While the odds of having AMD were higher in women with a vitamin D status below 12 ng/ml, researchers found that increasing vitamin D levels beyond 12 ng/ml didn’t seem to further lower the odds of AMD to a meaningful extent.
“These findings suggest that vitamin D may be another aspect of adequate nutrition one needs to consider when thinking about eye health,” Millen says. “The influence of nutrition on eye health may vary by one’s genetic risk for AMD; however, eating a healthy diet regardless of one’s genetic risk is recommended.”
Currently, the body of evidence linking vitamin D to AMD is not consistent, and more research is needed to understand vitamin D’s role in eye health.
“This is the first study examining associations between eye disease and the interaction between vitamin D and genetic risk,” Millen says. “One study alone cannot determine a causal association.”
She emphasizes the need for additional studies specifically designed with adequate power to test this question. “We need to see that our results are replicated in other studies before we should move the science forward with clinical trials,” she says.
Millen and her colleagues plan to conduct further research in this area. She has received funding from the National Institutes on Aging of the National Institutes of Health to examine associations between vitamin D and AMD in the Atherosclerosis Risk in Communities Study, which includes both men and women.
—Colleen Mullarkey
Reference
Millen AE, Meyers KJ, Liu Z, Engelman CD, Wallace RB, LeBlanc ES, et al. Association between vitamin D status and age-related macular degeneration by genetic risk. JAMA Ophthalmol. 2015 Aug 27. [Epub ahead of print].