Women who took a combination of folic acid and two B vitamins for several years had a lower chance of developing the most common cause of vision loss in older Americans, Harvard researchers report, the first rigorous trial to show a benefit from the supplements.
A team led by William G. Christen of Brigham and Women's Hospital and Harvard Medical School found that women who took a combination of folic acid and vitamins B6 and B12 had a 35 percent to 40 percent lower risk of developing age-related macular degeneration than the women who took a placebo. The results are reported in tomorrow's Archives of Internal Medicine.
"These are new findings and they need to be corroborated," Christen said in an interview. "If they are, they are potentially exciting and important."
The researchers randomly assigned more than 5,000 middle-aged women to receive either the supplements or a placebo to see who developed age-related macular degeneration. The first randomized clinical trial of the treatment to date was part of the Women's Antioxidant and Folic Acid Cardiovascular Study. It was also double-blinded, meaning neither the subjects nor the researchers knew what was contained in the pills each women was taking.
After more than seven years, 137 women were diagnosed with age-related macular degeneration. There were 55 cases in the group taking the folic acid, vitamin B6, and vitamin B12 combination compared to 82 cases in the placebo group.
The study's results stand in contrast to other findings from the cardiovascular study, which was designed to test whether the folic acid-vitamin B6 and B12 combination could prevent heart attacks or stroke in women who had a history of cardiovascular events or risk factors. Folic acid and the two B vitamins have been proven to lower levels of homocysteine in the blood, a substance linked to blood vessel damage such as atherosclerosis that in turn raises the risk of heart disease and stroke.
But the trial showed no benefit for women taking folic acid and vitamins B6 and B12 in reducing their risk for cardiovascular events. The disappointing results are consistent with other studies in which gold-standard randomized trials did not confirm what looked like a promising role for vitamins or other nutritional supplements in preventing disease, based on observations of people who chose to take them.
The current study about macular degeneration, which is based on data collected at the same time as the cardiovascular information, examined whether lowering homocysteine with these supplements would translate into a lower risk. Previous observational studies had implicated high homocysteine levels in the eye disease, which includes damage to small blood vessels in the eye.
"This is an important study regarding reducing the risk of age related macular degeneration," Dr. Evangelos Gragoudas, director of the retina service at Massachusetts Eye and Ear Infirmary, said in n e-mail interview. He was not involved in the study. "If the results are confirmed in specially designed studies involving the general population it could have a major impact in clinical practice."
Some treatments can help certain patients with an advanced form of the disease, but there is little that can be done for earlier stages, Christen said.
"Other than avoiding cigarette smoking, this would be the first identified means to reduce the risk of early age related macular degeneration," he said.
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