Vitamin D may play key role in preventing macular degeneration – UB News Center

BUFFALO, N.Y. – Vitamin D has been studied extensively in
relation to bone health as well as cancer. Now, a team led by a
researcher at the University at Buffalo has discovered that vitamin
D may play a significant role in eye health, specifically in the
possible prevention of age-related macular degeneration, or AMD,
among women who are more genetically prone to developing the
sight-damaging disease.

In a paper published today (Aug. 27) in JAMA Ophthalmology online,
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 Millen, PhD, 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 Millen.

Macular degeneration is characterized by the deterioration of
the macula, a small part of the central retina where the
eye’s photoreceptors (rods and cones) are most highly
concentrated. The leading cause of legal blindness, macular
degeneration affects more than 10 million Americans — more
than cataracts and glaucoma combined — according to the
American Macular Degeneration Foundation. The disease affects a
person’s central vision, which is needed for common tasks
such as reading and driving. The effect is similar to that of a
rain drop on the center of a camera lens.

Researchers analyzed data compiled on 1,230 women ages 54 to 74
who participated in the Carotenoids in Age-related Eye Disease
Study (CAREDS), which is 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, disability and poor
quality of life in postmenopausal women. UB is one of 40 WHI
centers nationally. CAREDS was conducted among participants at
three of the 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.

Human skin can synthesize vitamin D when exposed to ultraviolet
light, Millen explains. However, for many people, 15 to 30 minutes
a day with 10 percent of their skin exposed might be sufficient. In
winter months, when there is a lower solar angle, sun exposure may
not be not sufficient to maintain blood level for people who live
north of a line from about Washington, D.C., to Los Angeles. At
these times and locations, dietary intake may be needed. Dietary
sources of vitamin D include fortified foods such as milk and foods
that naturally contain vitamin D such as fatty fish like salmon and
mackerel.

“Macular degeneration has been found to be strongly
associated with genetic risk,” 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. This
gene codes for the CFH protein that is involved in the body’s
immune response to destroy bacteria and viruses.

Inflammation is believed to be involved in the development of
macular degeneration.  

“People who have early stage AMD develop drusen, lipid and
protein deposits that build up in the eye. Your body sees this
drusen as a foreign substance and attacks it, in part via the
complement cascade response,” explains Millen. “CFH is
one of the proteins involved in this response. We see more AMD in
people who have certain variants in the gene which encodes a form
of this CFH protein that is associated with a more aggressive
immune response.”

Vitamin D shows promise for protecting against macular
degeneration because of its anti-inflammatory and antiangiogenic
properties; antiangiogenic refers to slowing the growth of new
blood vessels, often seen in late stages of AMD.

“Our thinking was, if a person’s vitamin D status is
better, would it reduce the immune response to drusen? We wanted to
understand if the association between vitamin D and AMD differed
depending on a person’s genetic risk for AMD,” says
Millen. “Our study suggests that being deficient for vitamin
D may increase one’s risk for AMD, and that this increased
risk may be most profound in those with the highest genetic risk
for this specific variant in the CFH protein.”

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,” 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
Millen. “There wasn’t enough evidence at that time to
make any recommendation based on D status and other outcomes beyond
bone health.”

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.

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