MONDAY, June 14, 2004 (HealthDayNews) -- Bananas, oranges, and other fruits may reduce the risk of developing age-related macular degeneration, the leading cause of blindness among older people.
Scientists have found that people who ate at least three daily servings of fruit had a 36 percent lower risk of developing age-related macular degeneration (AMD) than people who ate fewer than 1.5 servings a day.
"This is the first good study that has some statistical value that documents what we've been thinking all along," said Dr. Robert Cykiert, a professor of ophthalmology at New York University School of Medicine in New York City. "It's always nice to have some statistical support for what's been observed but not proven."
More surprisingly, vegetables, vitamins and carotenoids, the compounds responsible for red, yellow and orange pigment in some fruits and vegetables, did not appear to affect the risk.
Although the findings need to be replicated, the study can still serve as a green light to eat fruit. "Fruit intake has been related to reduced cardiovascular disease and certain forms of cancer," said the study's lead author, Eunyoung Cho, an epidemiologist at Brigham and Women's Hospital and an instructor in medicine at Harvard Medical School, both in Boston. "I think it's still OK to say this is one more reason to eat fruit."
The findings appear in the June issue of The Archives of Ophthalmology.
Because there's little to be done about AMD once it sets in, researchers have been strongly focused on prevention. While some studies have found that antioxidant vitamin and mineral supplementation protects against AMD, there's been little research looking at fruit and vegetable intake in relation to the condition.
This study is the first large-scale prospective examination of diet and risk for AMD. "We looked at all antioxidant vitamins, carotenoids as well as fruits and vegetables, because they are good food sources of those nutrients," Cho explained.
In all, the study included 77,562 women who were part of the Nurses' Health Study and 40,866 men who were part of the Health Professionals Follow-up Study. All participants were at least 50 years old when they enrolled in the study and had no evidence of AMD.
Both men and women completed questionnaires about their food intake as well as vitamin and supplement use at different intervals. Women were followed for up to 18 years while men were followed for up to 12 years.
During that time, a total of 464 people (329 women and 135 men) developed early stage AMD, while 316 people (217 women and 99 men) developed neovascular (or "wet") AMD, a more severe version of the disease.
The more fruit a person ate, the less likely he or she seemed to develop neovascular AMD, although not early-stage AMD.
"But, contrary to previous studies, we didn't find any strong association between antioxidant vitamins and carotenoid intake and AMD," Cho said.
Of several fruits examined, oranges and bananas had the strongest association. "But others also had an inverse relationship and at this point we don't want to pinpoint any fruit item," Cho said.
No one knows why fruit might have this beneficial effect. However, fruit intake has been related to a reduced risk of cardiovascular disease, and neovascular AMD has been related to cardiovascular risk factors, both of which suggest that the answer may lie somewhere along this pathway.
"We need to know which component [of fruit] drives the risk, such as flavonoids, fiber, folate, potassium," Cho said. "Those are components in fruit that have been related to some health benefits, so other studies need to look at these components."
Isolating the specific components could lead to more efficient preventive measures. "Fruits contain dozens or maybe even hundreds of substances that either work separately or together to give this effect," Cykiert said. "It would be nice if we could isolate which ones work so we could put them into a vitamin."
In the meantime, Cykiert recommends that family members of his patients with macular degeneration take vitamins C and E, zinc and beta-carotene. Those nutrients have been shown to slow down macular degeneration in patients who already have it. "It seems to be a familial condition and it's not harmful to take them," he said.
More information
Visit the National Eye Institute for more on age-related macular degeneration.
