Two new studies offer tantalizing evidence that chemicals in green and yellow vegetables may protect against heart disease and the most common cause of blindness in the elderly.
But much more research will be needed to determine which of the antioxidant chemicals may be protective, in what quantities, over what periods of time and in what types of people, said researchers not involved in the work.The compounds, called carotenoids, are the colorful pigments that make squash yellow and spinach green.
Beta carotene is the best-known carotenoid, but it accounts for only about 25 percent of the carotenoids that the blood absorbs from food, and others are just beginning to be explored, researchers said.
In one new study, of 1,899 men with high blood cholesterol, those with high levels of carotenoids had 36 percent fewer heart attacks and deaths over 13 years than men with low levels of carotenoids in their blood.
"When we looked at men who never smoked, the protective effect was much greater," wrote Dr. Dexter Morris in Wednesday's issue of the Journal of the American Medical Association.
Nonsmokers with the highest blood levels of carotenoids had 70 percent fewer heart attacks than nonsmokers with the lowest levels, said researchers, led by Dr. Morris of the University of North Carolina, Chapel Hill.
In the other study, Harvard researchers compared 356 people who had developed a visual disorder called age-related macular degeneration with 500 similar people who were free of the condition. People who consumed the most dark green, leafy vegetables were 43 percent less likely to have developed AMD than people who had consumed the least, researchers said.
Those findings also are in Wednesday's JAMA and were being presented Tuesday at the AMA's Science Reporters Conference in Seattle.
"Increasing the consumption of foods rich in certain carotenoids, in particular dark green, leafy vegetables, may decrease the risk of developing advanced or exudative AMD, the most visually disabling form of macular degeneration among older people," said researchers, led by Dr. Johanna M. Seddon of the Massachusetts Eye and Ear Infirmary and Harvard Medical School
AMD causes vision loss in an estimated 13.1 million Americans and accounts for up to a third of the 900,000 U.S. cases of blindness, according to Prevent Blindness America.
Exudative AMD is a sub-type of the disease, in which tiny blood vessels grow under an area of the retina, causing scarring and hemorrhaging that block vision.