B-Complex Vitamin Supplements Reduce Risk of Macular Degeneration

Large supplemental amounts of three B-complex vitamins can significantly lower the risk of age-related macular degeneration (AMD) in women, according to a study by researchers at the Harvard Medical School.

AMD is the most common cause of blindness in seniors and is very difficult to treat. Smoking tobacco and low dietary intake of several nutrients, including lutein, zeaxanthin, and docosahexaenoic acid (an omega-3 fat) have previously been linked to a greater risk of AMD.

William G. Christen, ScD, and his colleagues asked 5,205 women to take either a combination of three B vitamins or placebos daily for an average of seven years. All of the women were at least 40 years of age, and they had been diagnosed with either cardiovascular disease or having at least three risk factors for cardiovascular disease.

The supplements contained 2,500 mcg (2.5 mg) of folic acid, 50 mg of vitamin B6, and 1,000 mcg (1 mg) of vitamin B12.

The researchers noted that the protective effect of the B vitamins appeared after two years and continued through the end of the study. Women taking the vitamin supplements had a 34 percent lower risk of developing AMD and a 41 percent lower risk of "visually significant" AMD.

In raw numbers, 55 women in the B-vitamin group developed some form of AMD, compared with 82 in the placebo group. In the B-vitamin group, 26 of the women developed a severe form of AMD, compared with 44 cases in the placebo group.

Christen noted the importance of the finding: "From a public health perspective, this is particularly important because persons with early AMD are at an increased risk of developing advanced AMD, the leading cause of irreversible vision loss in older Americans."

The researchers wrote that the B vitamins lower homocysteine levels, which might help maintain the integrity of blood vessels in the eyes.

In a separate study, researchers from Australia reported that relatively high blood levels of lutein, zeaxanthin, and lycopene were associated with a 33 percent lower risk of retinopathy, a type of eye disease in people with type-2 diabetes.

References: Christen WG, Glynn RJ, Chew EY, et al. Folic acid, pyridoxine, and cyanocobalamin combination treatment and age-related macular degeneration in women. Archives of Internal Medicine, 2009;169:335-341. Brazionis L, Rowley K, Itsiopoulos C, et al. Plasma carotenoids and diabetic retinopathy. British Journal of Nutrition, 2009;101:270-277.