A diet rich in certain antioxidants, such as vitamins C and E, may help prevent Alzheimer¿s disease, according to the results of two new studies. Scientists have known for some time that certain proteins accumulate in the brains of Alzheimer¿s patients, leading to nerve cell damage. Exactly what causes the toxic plaques to form has not been established, but researchers posit that so-called free radicals¿highly reactive, naturally occurring molecules that damage cellular structures¿play a role. If so, it would stand to reason that antioxidants, which have the ability to bind and inactivate these destructive radicals, can combat the plaques. The new findings, published today in the Journal of the American Medical Association, may strengthen that case.
In the first study, Marianne Engelhart of the Erasmus Medical Center in Rotterdam, the Netherlands, and her colleagues observed more than 5,000 Dutch subjects ages 55 and older. The team recorded the dietary habits of the participants at the onset of the study and repeatedly examined them for signs of dementia in the years that followed. Out of the original test group, 197 individuals developed Alzheimer¿s. Comparing the types of foods eaten by patients with and without the disorder, the investigators found that smokers who consistently dined on foods rich in vitamins C and E were less likely to fall victim to the disease than were smokers who did not have high-antioxidant diets. Nonsmokers did not exhibit this pattern. The team notes that smoking may itself increase the production of free radicals, and thus spur Alzheimer¿s progression. If so, antioxidants may help offset that additional risk by reducing the smoker¿s larger load of free radicals.
In the second study, Martha Morris of Rush-Presbyterian St. Luke¿s Medical Center in Chicago and her colleagues examined 815 of the city¿s residents, all ages 65 and older. They found that dietary vitamin E intake was associated with a reduced risk of developing Alzheimer¿s, but only in patients lacking the APOE E4 gene variant associated with the disease. Notably, for subjects in that subset who ranked in the top fifth of vitamin E intake, risk of the disease was 67 percent lower than that of participants in the bottom fifth. Neither team observed a positive effect from vitamin supplements.
"These two studies do not provide the final answer as to whether antioxidant vitamins are truly protective against [Alzheimer¿s]," Daniel J. Foley of the National Institute of Aging in Bethesda, MD., and Lon R. White of the Pacific Health Research Institute in Hawaii, write in accompanying editorial. "Nonetheless, the idea that vitamin E and vitamin C might have beneficial effects on the underlying AD process makes sense." Studies tracking a greater number of people for a longer period of time may produce more telling results.