A study of more than 5,000 men and women found that people who consumed very high amounts of dark green, yellow, and red vegetables actually appear to reduce their risk of dementia by about 25%, according to study co-author Monique M.B. Breteler, with the Erasmus Medical Center in Rotterdam, Netherlands.
But while most scientists and researchers agree that eating a healthy diet can protect the heart and bones, Breteler tells WebMD it is "too soon" to say that antioxidants found in those vegetables actually do protect against Alzheimer's disease.
If antioxidants do prove to protect against Alzheimer's disease, it is probably because they reduce what is called "oxidative stress" in cells. Consumption of some foods, such as foods high in fat, increases the oxidative stress by producing free radicals.
Free radicals have been associated with other bad effects of aging -- from skin problems to declining eyesight, according to Robert P. Friedland, MD, chief of the neurogeriatrics laboratory at Case Western Reserve University School of Medicine. "We think the free radicals are doing the same thing in the brain." So while high fat diets increase production of free radicals, antioxidants "scavenge for free radicals and thus may reduce oxidative stress," he says.
Friedland tells WebMD that Breteler is probably on the right track, so much so that he thinks it is time to make some general recommendations about preventing Alzheimer's disease. Age and genetics cannot be altered by lifestyle, Friedland says, but he offers a "to-do" list for those who want to improve their chances of maintaining a healthy brain.
He suggests that you:
- Eat a diet high in antioxidants.
- Eat fish.
- Take vitamin E.
- Take B vitamins.
- Take folic acid.
- Be mentally and physically active throughout life.
- Avoid head injuries.
Bill Thies, PhD, vice president of medical and scientific affairs for the Alzheimer's Association, says that although Friedland's recommendations are probably useful and that he agrees with all of them, he wants to "be very clear that the association is not making any recommendations about ways to prevent Alzheimer's. All of the studies thus far are observational studies, and we cannot make recommendations based on observation alone."
Breteler, too, insists on caution. She says that she and others at the Erasmus Medical Center just "observed what appears to be a relationship," but can't really say that there is a cause and effect relationship.
They studied the dietary patterns of more than 5,000 people without dementia who volunteered to participate in the Rotterdam study, which looks at many aspects of aging. Breteler has been following this group of people since 1990 and, in that time, 146 people developed Alzheimer's disease and another 29 have dementia caused by stroke.
Breteler says the protective effect of antioxidants was "more pronounced among smokers and among those who are carriers of the Alzheimer's gene." She also says the antioxidants beta-carotene, vitamin C, and vitamin E appear to be equally protective but "flavonoids and/or fruit do not appear to be effective."
Grace J. Petot, MS, RD, assistant professor at Case Western Reserve University, tells WebMD that Breteler's results confirm some earlier studies that point to antioxidants as a way to lower risk of dementia. For example, she says that she followed a group of people who carry the Alzheimer's gene and found that "vegetables, especially dark leafy vegetables, appear to be protective."
Although Breteler was reluctant to say how many servings of dietary antioxidants are "high consumption," Petot says "adding about one and a half servings daily was protective in other studies." Petot says that "the current dietary recommendations are for five servings of fruits and vegetables -- and no one really eats five servings."
For more information from WebMD, visit our Disease and Conditions Alzheimer's page.