CHICAGO -- February 23, 2009 -- Taking a combination of vitamins B6 and B12 and folic acid appears to decrease the risk of age-related macular degeneration (AMD) in women, according to a study published in the February 23 issue of Archives of Internal Medicine.
William G. Christen, Brigham and Women's Hospital, and Harvard Medical School, Boston, Massachusetts, and colleagues conducted a randomised, double-blind trial involving 5,442 women aged 40 years and older who already had heart disease or at least 3 risk factors. Of these, 5,205 did not have AMD at the beginning of the study.
In April 1998, the women were randomly assigned to take a placebo or a combination of folic acid 2.5 mg per day, vitamin B6 50 mg per day, and vitamin B12 1 mg per day. Participants continued the therapy through July 2005 and were tracked for the development of AMD through November 2005.
Over an average of 7.3 years of treatment and follow-up, 137 new cases of AMD were documented, including 70 cases that were visually significant (resulting in a visual acuity of 20/30 or worse). Of these, 55 AMD cases -- 26 visually significant -- occurred in the 2,607 women in the active-treatment group, whereas 82 of the 2,598 women in the placebo group developed AMD, 44 cases of which were visually significant.
Women taking the supplements had a 34% lower risk of any AMD and a 41% lower risk of visually significant AMD. "The beneficial effect of treatment began to emerge at approximately 2 years of follow-up and persisted throughout the trial," the authors wrote.
"The trial findings reported herein are the strongest evidence to date in support of a possible beneficial effect of folic acid and B vitamin supplements in AMD prevention."
Because the findings apply to the early stages of disease development, these supplements appear to represent the first identified way -- other than not smoking -- to reduce the risk of AMD in individuals at an average risk. "From a public health perspective, this is particularly important because persons with early AMD are at increased risk of developing advanced AMD, the leading cause of severe, irreversible vision loss in older Americans," wrote the authors.
Beyond lowering homocysteine levels, potential mechanisms for the effectiveness of B vitamins and folic acid in preventing AMD include antioxidant effects and improved function of blood vessels in the eye, the authors noted.
SOURCE: Archives of Internal Medicine
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