B vitamins may ward off age-related vision loss

Taking folic acid and vitamin B6 and B12 may help women preserve their eyesight as they age, a new study out in the Archives of Internal Medicine shows.

Among 5,205 women 40 and older, those who had been randomly assigned to take the vitamin combo were about 35 percent less likely to develop age-related macular degeneration (AMD), a deterioration of the retina that is the leading cause of vision loss among older US adults.

“There’s no way other than avoiding cigarette smoking to reduce the risk of the onset of age-related macular degeneration, and this is the first suggestion that maybe there’s something else we can do,” Dr. William G. Christen of Brigham and Women’s Hospital and Harvard Medical School in Boston, a researcher on the study, told Reuters Health. But the findings must be confirmed before the vitamins can be recommended for AMD prevention, he added.

Studies have linked high levels of homocysteine, a byproduct of protein metabolism, to AMD risk, while elevated homocysteine is a known risk factor for heart and blood vessel disease, Christen and his team note in their report. Taking folic acid, B6, and B12 can lower homocysteine levels.

To investigate whether it might also cut AMD risk, the researchers looked at women participating in a study evaluating the effects of the vitamin combination on heart disease risk. Study participants had been assigned to take 2.5 milligrams of folic acid, 50 milligrams vitamin B6, and 1 milligram of vitamin B12 daily or to a placebo group. “These are a number of times more the doses you would get in a simple multivitamin,” Christen noted.

All of the women had heart disease or at least three heart disease risk factors, such as high blood pressure or diabetes.

During 7.3 years of follow-up, 137 of the study participants developed AMD, 70 of whom had significant visual impairment. Two years into the study, women taking the vitamins began showing a reduced risk of AMD compared to women taking placebo. Overall, 55 women taking the vitamins developed AMD, compared to 80 women in the placebo group; 26 in the vitamin group had visually significant disease, compared to 44 of women on placebo. Women taking the vitamins were thus 34 percent less likely to develop AMD, and at 41 percent lower risk of visually significant AMD.

It’s not clear whether the vitamins protected eyesight by lowering homocysteine levels, exerting antioxidant effects, or improving blood vessel function, Christen and his colleagues say. More research should be done to clarify the mechanism, they conclude, and to confirm the findings in other groups of people.

SOURCE: Archives of Internal Medicine, February 23, 2009.

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