In a paper published recently published in JAMA Ophthalmology online, Dr. Amy Millen, associate professor of epidemiology and environmental health in UB’s School of Public Health and Health Professions, and her team found that women who are deficient in vitamin D and have a specific high-risk genotype are 6.7 times more likely to develop AMD than women with sufficient vitamin D status and no high risk genotype.
“Most people have heard that you should eat carrots to help your vision. However, there appear to be many other ways that adequate nutrition can support eye health. Having adequate vitamin D status may be one of them,” says Dr. Millen, the study’s lead author. “This is not a study that can, alone, prove a causal association, but it does suggest that if you’re at high genetic risk for AMD, having a sufficient vitamin D status might help reduce your risk.”
“To our knowledge, this is the first study that’s looked at the interaction between genetic risk and vitamin D status in the context of age-related eye disease,” adds Dr. Millen.
Researchers analyzed data compiled on 1,230 women ages 54 to 74 who participated in the Carotenoids in Age-related Eye Disease Study (CAREDS), an ancillary study of the Women’s Health Initiative (WHI) Observational Study (OS). The WHI OS is a major National Institutes of Health-funded research program aimed at addressing the most common causes of death and disability in postmenopausal women. UB is one of 40 WHI centers nationally. CAREDS was conducted at three WHI OS centers: University of Wisconsin (Madison), the University of Iowa (Iowa City) and the Kaiser Center for Health Research (Portland, Oregon).
Researchers were able to determine participants’ vitamin D status by analyzing serum samples for a vitamin D biomarker, 25-hydroxyvitamin D [25(OH)D], which provided a glimpse into vitamin D intake through all sources: diet, supplements and sunlight.
Macular degeneration has been found to be strongly associated with genetic risk,” Dr. Millen says. “Among many genes linked to AMD, one of the strongest is a specific genetic variant (Y402H) in the complement factor H gene, called CFH for short. We see more AMD in people who have certain variants in the gene which encodes a form of the CFH protein that is associated with a more aggressive immune response.”
The study results, however, shouldn’t prompt people to run to the nearest grocery store to purchase vitamin D supplements.
“Our message is not that achieving really high levels of vitamin D are good for the eye, but that having deficient vitamin D levels may be unhealthy for your eyes,” Dr. Millen says.
Although the odds of having AMD was higher in women who were deficient for vitamin D, with 25(OH)D levels below 12 ng/mL (30 nmol/L), increasing vitamin D levels beyond 12 ng/mL did not further lower the odds of AMD to any meaningful extent, she explains.
“This study supports a role for vitamin D in eye health. That’s significant because when the Institute of Medicine’s report on the dietary reference intakes for vitamin D and calcium were released in 2011, the committee could only make conclusions about D related to bone health,” says Dr. Millen. “There wasn’t enough evidence at that time to make any recommendation based on D status and other outcomes beyond bone health.”
Dr. Millen’s co-authors on the paper, titled “Association between vitamin D status and age-related macular degeneration by genetic risk,” include researchers from the University of Wisconsin-Madison, University of Iowa, Case Western Reserve University, Kaiser Permanente Center for Health Research and Fred Hutchinson Cancer Research Center. The study was funded by the National Eye Institute of the National Institutes of Health.