April 11, 2011 -- Women younger than 75 who get sufficient vitamin D in their diets appear to have a reduced risk of a leading cause of blindness, new research indicates.
In the study, researchers say women under 75 who got the most vitamin D had a 59% decreased risk of developing age-related macular degeneration, compared to women with the lowest vitamin D intake.
Researchers also found that the women who had a blood vitamin D level higher than 38 nmol/L had a 48% decreased risk of early age-related macular degeneration (AMD). A blood level of 50 nmol/L is considered sufficient, according to the Institute of Medicine.
The top food sources of vitamin D among women in the study were milk, fish, fortified margarine, and fortified cereal. No correlation was found between self-reported time in direct sunlight, which is also a source of vitamin D, and AMD.
Macular Degeneration Causes Irreversible Vision Loss
Age-related macular degeneration is a chronic, late-onset disease that results in degeneration of the macula, the central portion of the retina that allows for focused, precise vision. It is the leading cause of adult irreversible vision loss and affects about 8.5 million Americans aged 40 and older, the researchers say.
Study author Amy E. Millen, PhD, of the University of Buffalo, and colleagues studied data from 1,313 women to investigate whether a well-known blood test for vitamin D status might be associated with early age-related macular degeneration.
The blood test, called serum 25 (OH) D, measures vitamin D exposure from oral sources and sunlight, Millen says in a news release.
Previous Research Has Found Similar Vitamin D Benefit
The researchers say that their study is the second to find an association between age-related macular degeneration and vitamin D levels. More studies are needed to verify their findings, the researchers say, as well as to understand more about the potential interaction between vitamin D levels and genetic and lifestyle factors concerning the risk of early development of macular degeneration.
The study is published in the April issue of the Archives of Ophthalmology.