The study's authors did not strictly define the type and severity of eye disease. (CBC)

Taking a combination of folic acid and B vitamins may help to prevent a common form of vision loss in older women, according to a new study.

Age-related macular degeneration is a degenerative disease of the macula, a small area at the centre of the retina. The overgrowth of blood vessels into the retina can lead to central vision loss, preventing sufferers from seeing fine details, recognizing faces, or reading and driving.

It is a leading cause of vision loss in older Americans, and more than a third of Canadians between the ages of 55 and 74 develop AMD, according to the AMD Canada website.

In Monday's issue of the Archives of Internal Medicine, William Christen, of Brigham and Women's Hospital and Harvard Medical School in Boston, and his colleagues reported the results of their randomized double-blind clinical trial involving more than 5,000 women aged 40 and older.

"Other than avoiding cigarette smoking, this is the first suggestion from a randomized trial of a possible way to reduce early stage AMD," said Christen, who led the research.

The findings should also apply to men, he said.

In the study, participants who took a combination of vitamin B6, vitamin B12 and folic acid reduced their risk of macular degeneration by more than a third after seven years, compared with women who took placebos.

The strengths of the study were its random design and long follow-up, said Allen Taylor, director of the Laboratory for Nutrition and Vision Research at Tufts University in Boston.

Because the results were based on a study for heart disease, the study's authors did not strictly define the type and severity of eye disease, added Taylor, who does similar research but was not involved in this study.

The team found:

• 55 cases of AMD among women taking the vitamins, compared with 82 cases in the placebo group.
• 26 cases of more significant vision loss (resulting in a visual acuity of 20/30 or worse) among those in the vitamin group, compared with 44 among those taking the sugar pills.

The researchers speculated that folic acid and B vitamins may help by lowering levels of homocysteine, an amino acid that can damage the lining of blood vessels and is linked with heart disease risk.

Blood vessel size

The beneficial effect began to emerge about two years into the follow-up and lasted throughout the trial.

Earlier studies concluded that the supplements were not helpful for cardiovascular disease, but it could be that the small blood vessels in the eye respond better than the body's large blood vessels, the researchers said.

The vitamins could also work through antioxidant effects

Christen advised that it's too soon to recommend taking B vitamins to prevent age-related vision loss.

People who already have the disease could talk to their doctors about taking over-the-counter supplements that include vitamins C, E and zinc, which research suggests slows the disease.

Foods that are rich in B vitamins and folic acid include: meat, poultry, fortified cereals, beans, nuts, leafy vegetables, spinach, and peas.

Folate is a B vitamin that the body uses to make healthy new cells. The synthetic version, folic acid, is used to fortify grain products such as white flour.

The research was funded by the U.S. National Institutes of Health.

BASF Corp. and Cognis Corp. provided the vitamins and placebos but had no other involvement in the study. Some of the researchers said they had received funding from pharmaceutical and nutritional supplement makers.

With files from Associated Press