In addition, the combined B vitamin supplements were associated with a 41 per cent reduced risk of visually significant AMD, according to findings of a randomised, double-blind clinical trial involving 5,442 women age 40 and older.
The researchers, led by William Christen from the Brigham and Women's Hospital and Harvard Medical School, published their findings in the Archives of Internal Medicine.
Despite the fact that approximately 25 to 30 million people worldwide are affected by AMD, awareness of the condition is low, according to AMD Alliance International. And as the generation of Baby Boomers gets older, the Alliance expects incidence to be on the rise and triple by 2025.
AMD is a degenerative retinal disease that causes central vision loss and leaves only peripheral vision. Early detection is cited as a means of prevention so that treatment or rehabilitation can be undertaken early enough. However, links to diet have also been underscored.
Building on the findings of recent studies that reported a correlation between AMD and blood levels of an amino acid called homocysteine, linked to dysfunction of the blood vessel lining. Added to this are observations that supplementation with vitamins B6 and B12, and folic acid may reduce homocysteine levels and reverse this blood vessel dysfunction.
Christen and his co-workers recruited women with heart disease or at least three risk factors for the disease. Of these, 96 per cent of the women did not have AMD at the start of the study. The women were randomly assigned to receive either 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).
Over the course of 7.3 years of intervention and follow-up, the researchers documents 137 new cases of AMD, of which 70 cases were visually significant.
The combined B vitamin supplement was associated with a 34 per cent lower risk of any AMD and a 41 per cent lower risk of visually significant AMD, said the researchers. . "The beneficial effect of treatment began to emerge at approximately two years of follow-up and persisted throughout the trial," wrote the authors.
"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," they added.
Importantly, the researchers added that, because the results apply to the early stages of disease development, they appear to represent the first identified, besides 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," they said.
Commenting on the potential mechanism, Christen and his co-workers note that, beyond lowering homocysteine levels, other modes of action include antioxidant effects and improved function of blood vessels in the eye.
Prevention is key
The results were welcomed by Andrew Shao, PhD, vice president, scientific and regulatory affairs, for the Council for Responsible Nutrition (CRN), a supplements trade association, who called the results very promising.
“Currently, there are very few treatment options available for AMD, so prevention is key,” said Dr Shao. “The results of this study suggest that B vitamins could be combined with other supplemental nutrients including the antioxidants, vitamins C and E and carotenoids beta-carotene and lutein, which have also been shown to lower the risk of AMD.
“These supplements in turn, can be added to other preventive measures, including avoiding smoking and excessive sun exposure to provide even further protection.”
Source: Archives in Internal Medicine2009, Volume 169, Issue 4, Pages 335-341“Folic Acid, Pyridoxine, and Cyanocobalamin Combination Treatment and Age-Related Macular Degeneration in Women: The Women's Antioxidant and Folic Acid Cardiovascular Study”Authors: W.G. Christen, R.J. Glynn, E.Y. Chew, C.M. Albert, J.E. Manson