NEW YORK (Reuters Health) - Diets rich in vitamin C and E may delay the onset of memory-robbing Alzheimer's disease , two studies in the June 26th issue of The Journal of the American Medical Association suggest.Compounds called free radicals that are released during normal cell processes can be harmful to body tissues, leading to so-called oxidative damage or stress. Experts have linked oxidative stress to several illnesses, including cancer, heart disease and Alzheimer's disease.
Since antioxidants--including vitamins C and E--can neutralize free radicals, some experts believe these nutrients could help delay the onset of Alzheimer's disease.
In the first study, lead author Dr. Marianne J. Engelhart of the Erasmus Medical Center in Rotterdam, the Netherlands, and colleagues reviewed dietary information for 5,395 men and women at least 55 years old who were free of dementia.
After 6 years, 146 people in the group were diagnosed with Alzheimer's disease, the researchers report.
Engelhart's team found that those with the highest intake of vitamin C and vitamin E from food appeared to be the least likely to develop Alzheimer's disease. Smokers who consumed the most beta-carotene and flavonoids--two types of antioxidant nutrients--also appeared to cut their Alzheimer's risk.
However, whether the findings reflect a "causal association" between dietary consumption of antioxidants and a reduction in a person's risk of Alzheimer's disease "remains to be elucidated," the authors conclude.
In the second study, lead author Dr. Martha Clare Morris of the Rush Institute for Healthy Aging in Chicago, Illinois, and colleagues also aimed to identify any relationship between dietary consumption of antioxidants and risk of developing Alzheimer's disease.
Morris and colleagues studied 815 men and women aged 65 and older. After 3.9 years, 131 were diagnosed with Alzheimer's.
They found that those with the highest dietary intake of vitamin E had the lowest risk of developing Alzheimer's disease. But people who carried a gene known to increase Alzheimer's risk did not see any benefit from vitamin E consumption.
Neither of the studies showed any reduction in the risk of developing Alzheimer's among people who took dietary supplements like daily vitamin pills that contained antioxidants. A benefit only appeared when the nutrients were consumed in food.
This finding, in itself, suggests that perhaps some other component of food slows progression of Alzheimer's disease, Daniel J. Foley of the National Institute on Aging in Bethesda, Maryland and Dr. Lon R. White of Pacific Health Research Institute in Honolulu, Hawaii, explain in an accompanying editorial.
Nonetheless, "the similarity of the results (of the two studies)...provides persuasive support for the idea that antioxidant vitamins (in food) may have a beneficial impact on the development of Alzheimer's disease," Foley and White write.
"However, both studies have limitations and caveats that may undermine their validity," the editorialists add.
SOURCE: The Journal of the American Medical Association 2002;287:3223-