A new study shows people who drank fruit and vegetable juices more than three times a week were 76 percent less likely to develop Alzheimer's disease than those who drank juices less than once a week.
Researchers say the results suggest that a class of antioxidants found in fruit and vegetable juices called polyphenols may have a protective effect on the brain and help fight dementia and Alzheimer's disease.
Polyphenols are found in fruits and vegetables, primarily in the skins and peels, and are abundant in juices, teas, and wine.
Juice Fights Alzheimer's Disease
In the study, published in The American Journal of Medicine, researchers followed nearly 2,000 Japanese-American adults from King County, Wash., for 10 years. The participants were aged 65 or older and were free of signs of Alzheimer's or dementia at the start of the study. Self-reported dietary information was obtained from 1,589 of the adults. The average age of this group was 72 years at the start of the study.
Previous studies show Japanese adults living in Japan have a lower incidence of Alzheimer's disease. But Japanese people living in the U.S. have higher rates of the disease, which suggests that environmental factors such as diet and lifestyle may play an important role in the development of Alzheimer's disease.
After adjusting for possible confounding factors, like smoking, educational status, and physical activity, the researchers found people who drank fruit and vegetable juices more than three times a week had a 76 percent lower risk of probable Alzheimer's disease compared with those who drank juice less than once a week. Drinking fruit or vegetable juice once or twice a week was associated with a 16 percent lower risk.
In addition, the study showed the protective benefits of juice appeared to be particularly enhanced in people who had a genetic marker linked to an increased risk of Alzheimer's disease known as apolipoprotein E C%-4 allele.
They also found no relationship between dietary intake of vitamins C and E, beta carotene, or tea and the risk for Alzheimer's disease.
Researchers say these results are only preliminary and more study is needed to confirm the relationship between polyphenols and Alzheimer's disease. Other recent studies looking at diet and supplement use with risk for Alzheimer's disease have not been consistent.
They say the next step will be to determine which fruit and vegetables juices might provide the biggest protective benefits.
"We don't know if it is a specific type of juice [that reduces risk]. That information was not collected in the current study," says researcher Qi Dai, M.D., Ph.D., of Vanderbilt School of Medicine, in a news release.
This study was supported by the National Institute on Aging.
SOURCES: Dai, Q., The American Journal of Medicine, September 2006; vol. 119: pp 751-759. News release, The American Journal of Medicine. News release, Vanderbilt University Medical Center.
By Jennifer Warner
Reviewed by Louise Chang, M.D