Lee Swanson Research Update

B Vitamins May Prevent Blindness in Females

March 2009

A combination of folic acid and vitamins B-6 and B-12 may reduce the risk of age-related macular degeneration (AMD) by 34%, according to a new study.

In addition, the combined B-vitamin supplements were associated with a 41% reduced risk of visually significant AMD, according to findings of a randomized, 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.

Research built 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 B-6 and B-12 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% 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 B-6 (50 mg per day) and vitamin B-12 (1 mg per day).

Over the course of 7.3 years of intervention and follow-up, the researchers documented 137 new cases of AMD, of which 70 cases were visually significant.

The combined B-vitamin supplement was associated with a 34% lower risk of any AMD and a 41% 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.

The results of the study apply to the early stages of disease development. "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," researchers said.

Commenting on the potential mechanism, Christen and his co-workers noted that, beyond lowering homocysteine levels, other modes of action include antioxidant effects and improved function of blood vessels in the eye.

Archives in Internal Medicine 169(4):335-341, 2009.

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