TUESDAY, June 25, 2002 (HealthDayNews) -- Remembering to eat foods with plenty of antioxidants now could help prevent memory loss later in life.
Two studies that looked at the effect of diet on memory in thousands of people found that antioxidants in food appear to shield the brain from Alzheimer's disease. One study saw the effect from both vitamin C and vitamin E, while the other detected it in vitamin E alone.
However, neither found that vitamin supplements could protect the brain from the degenerative disease, which affects 360,000 Americans each year and some 4 million overall in this country. Foods that are rich in antioxidants include citrus fruits, leafy green vegetables, vegetable oils and nuts.
Earlier work in animals has suggested that antioxidants -- chemicals that mop up renegade oxygen molecules that can harm cells -- may protect the brain from degeneration and even improve mental function. However, the new work, appearing in tomorrow's issue of the Journal of the American Medical Association, is the first to show such an effect in people.
"These studies are the first to provide evidence for a direct link between dietary antioxidant intake and Alzheimer's disease," says Martha Clare Morris, an epidemiologist at Rush-Presbyterian-St. Luke's Medical Center in Chicago and a co-author of one of the papers. Morris' group found that people 65 or over who consumed the most vitamin E in food -- though not supplements -- had about a 70 percent lower risk of developing Alzheimer's than those who ate the least.
People in the top fifth of vitamin E intake consumed an average of 11.4 international units a day of the nutrient, according to their responses on a diet survey. That's about half the government's recommended intake, and about twice the figure for those in the lowest quintile. The subjects were followed for an average of about four years.
Morris' group also found the protective effect of vitamin E on memory appears to be limited to people who don't have a gene called apolipoprotein E4 (ApoE4). This gene has been strongly linked to Alzheimer's, and about a third of the 815 volunteers in her study carried one.
The second study, by researchers in the Netherlands, looked at antioxidant intake and dementia risk in nearly 5,400 Dutch men and women followed for up to about a decade. During that time, 197 developed dementia, of which 146 cases were diagnosed as Alzheimer's.
High intake of vitamins C and E was associated with a lower risk of Alzheimer's -- 43 percent lower for those in the top third of consumption compared with those in the bottom third.
However, the effect was limited to the 20 percent of the volunteers who were current smokers. For them, two other antioxidants, flavonoids and beta carotene, were also protective. On the other hand, nonsmokers in the Chicago study did see a benefit from eating foods with plenty of vitamin E.
Also unlike the Chicago study, the Dutch researchers found that eating lots of vitamin E could reduce the risk of Alzheimer's even in people with the ApoE4 gene.
Dementia experts say the two studies have many important consistencies -- and several puzzling differences. As a result, "we're still in a state of not being able to state conclusively that antioxidants may reduce the risk of Alzheimer's disease," says Daniel Foley, an epidemiologist at the National Institute on Aging, which helped fund both projects.
Foley, co-author of an editorial accompanying the journal articles, says it's possible the two studies haven't identified an effect of antioxidants at all. People who eat lots of these compounds are also highly likely to be otherwise healthy, fit and well. "You may be picking up some other, unmeasured effect," Foley says. In other words, more research is needed to either cement the connection or dispel it.
William Thies, vice president for medical and scientific affairs for the
Alzheimer's Association, calls the studies "interesting" and says they confirm earlier data. However, "they don't really prove anything, they just show relationships," Thies adds.
Several trials are now under way to see if vitamin E can prevent or delay Alzheimer's. Thies says results from these studies are a year or two away. "I think we will get an answer to this question," he says. "But if these vitamins really do have an effect, it will be a relatively small one."
What To Do
For more on Alzheimer's disease, try the Alzheimer's Association. You can also try the National Institute on Aging. To learn more about antioxidants, visit the National Institutes of Health.
