Nutrients found to cut macular degeneration risk

CHICAGO (Reuters) - Taking vitamin D and eating fish -- especially those high in omega-3 fatty acids -- may reduce the risk of the most common cause of blindness among the elderly, researchers said on Monday.

Doctors do not know how to prevent age-related macular degeneration, the leading cause of blindness after age 60, but two studies in the Archives of Ophthalmology suggest nutrient-based treatments may help.

Age-related macular degeneration or AMD occurs when the macula, an area at the back of the retina, breaks down over time. The central vision of the eye becomes blurred.

Researchers evaluated 4,519 people aged 60 to 80 between 1992 and 1998 who took part in a trial sponsored by the National Institutes of Health's National Eye Institute.

First, patients were assessed for signs of macular degeneration and, if they had it, researchers determined how far it had progressed. Patients also completed a food questionnaire that measured intake of certain vitamins, minerals and other essential nutrients such as fatty acids.

One type of omega-3 fatty acid called docosahexaenoic acid or DHA -- commonly found in fatty fish such as salmon and tuna -- is believed to play an important role in the normal function of the retina.

Of the total, 1,115 patients had no symptoms of disease at the outset, while 658 people had a severe form of the disease. When their diets were evaluated, the researchers found that people who ate more fish -- more than two medium servings per week or more than one serving of broiled or baked fish -- were least likely to have the disease.

The study confirms prior research suggesting omega-3 fatty acids help ward off macular degeneration. The authors believe fatty acids may promote cell survival and bolster blood vessel function, reduce inflammation and maintain energy balance.

A second team of researchers analyzed data from 7,752 people taking part in a large national study between 1988 and 1994. Eleven percent of the patients had AMD.

The researchers found that vitamin D was associated with reduced risk of early AMD, but not advanced AMD.

When participants were split into five groups based on level of vitamin D in the blood, those in the highest group had a 40 percent lower risk of early AMD than those in the lowest group.

"The study provides evidence that vitamin D may protect against AMD," the researchers wrote.

They suggested Vitamin D may cut the risk of early age-related macular degeneration by reducing inflammation or preventing blood vessel growth in the retina.

The authors said there was not enough evidence to say how much fish or vitamin D people need, but the findings suggest the effect is worth more study, especially in the light of an aging U.S. population.

Omega-3 fatty acids have been shown to reduce the risk of heart disease, and researchers are now studying whether they can slow the progression of Alzheimer's disease.

Macular degeneration is the leading cause of blindness in older adults in the United States and the developed world, affecting about 25 million to 30 million people.