According to a report in the Archives of Internal Medicine, taking a combination of vitamins B6 and B12 and folic acid appears to decrease the risk of age-related macular degeneration in women.
Age-related macular degeneration is a leading cause of vision loss in older Americans, affecting 28 percent of people aged 75 and older. Macular degeneration affects the macula, the part of the eye that allows you to see fine detail. Treatment options exist for those with severe cases of macular degeneration, but the only known prevention method is to avoid smoking. Recent studies have drawn a connection between macular degeneration and blood levels of homocysteine, an amino acid. High levels of homocysteine are associated with dysfunction of the blood vessel lining, whereas treatment with vitamin B6, vitamin B12 and folic acid appears to reduce homocysteine levels and may reverse this blood vessel dysfunction.
The researchers conducted a randomized, double blind clinical trial involving 5,442 women age 40 and older who already had heart disease or at least three risk factors. Of these, 5,205 did not have macular degeneration at the beginning of the study. In April 1998, these women were randomly assigned to take a placebo or a combination of folic acid (2.5 milligrams per day), pyridoxine hydrochloride (vitamin B6, 50 milligrams per day) and cyanocobalamin (vitamin B12, 1 milligram per day). Participants continued the therapy through July 2005 and were tracked for the development of macular degeneration through November 2005.
Over an average of 7.3 years of treatment and follow-up, 137 new cases of macular degeneration were documented, including 70 cases that were visually significant (resulting in a visual acuity of 20/30 or worse). Of these, 55 macular degeneration 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 macular degeneration, 44 cases of which were visually significant. Women taking the supplements had a 34 percent lower risk of any macular degeneration and a 41 percent lower risk of visually significant macular degeneration. “The beneficial effect of treatment began to emerge at approximately two years of follow-up and persisted throughout the trial,” the authors write.
“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 macular degeneration prevention,” the authors write. Because they apply to the early stages of disease development, they appear to represent the first identified way, other than not smoking, to reduce the risk of macular degeneration in individuals at an average risk. “From a public health perspective, this is particularly important because persons with early macular degeneration are at increased risk of developing advanced macular degeneration, the leading cause of severe, irreversible vision loss in older Americans.”
Beyond lowering homocysteine levels, potential mechanisms for the effectiveness of B vitamins and folic acid in preventing macular degeneration include antioxidant effects and improved function of blood vessels in the eye, they note.
References:
1. American Medical Association. Arch Intern Med. 2009;169[4]:335-341.
