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Lori J. Shanks
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Taking a combination of vitamins B6 and B12 and folic acid appears
to decrease the risk of age-related macular degeneration in women,
according to a report in the February 23 issue of Archives of Internal Medicine, one of the JAMA/Archives
journals. Age-related macular degeneration (AMD) is a leading cause of
vision loss in older Americans, according to background information in
the article. Treatment options exist for those with severe cases of the
disease, but the only known prevention method is to avoid smoking.
Recent studies have drawn a connection between AMD 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.
William G. Christen, Sc.D., of Brigham and Women's Hospital and
Harvard Medical School, Boston, and colleagues 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 AMD 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 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 percent lower risk
of any AMD and a 41 percent lower risk of visually significant AMD.
"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 AMD 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 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."
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,
they note.
Source: JAMA and Archives Journals
Original article: William G. Christen, Robert J. Glynn, Emily Y. Chew, Christine M. Albert, JoAnn E. Manson (2009). Folic Acid, Pyridoxine, and Cyanocobalamin Combination Treatment and Age-Related Macular Degeneration in Women: The Women's Antioxidant and Folic Acid Cardiovascular Study. Arch Intern Med. 2009;169(4):335-341.
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