Lead researcher Dr. Qi Dai of Vanderbilt University and colleagues tracked the fruit and vegetable juice consumption of 1,836 dementia-free Seattle-area volunteers over a period of 10 years. They evaluated their cognitive function at two-year intervals.

After controlling for such potentially confounding factors as smoking, education, physical activity and fat intake, the investigators found that those who drank fruit or vegetable juices more than three times a week were 76 percent less likely to develop Alzheimer's than those who consumed juice less than once a week.

Their findings are published in the American Journal of Medicine.

The study did not say which kinds of juices were best at lowering Alzheimer's risk. However, earlier research suggests that red and orange fruit and vegetables, as well as berries, are rich sources of antioxidants.

The latest study adds to the mounting evidence that diet plays an important role in the development and onset of the disease.

Earlier research has shown that a diet rich in fruit, vegetables, whole grains, fish and a little red wine -- the so-called "Mediterranean" diet -- can lower the risk of Alzheimer's by 40 percent.

Turmeric, the main ingredient in curry, has been credited with improving mental function and warding off dementia. Regular consumption of green tea also appears to dramatically lower the risk of age-related dementia.

Previous studies have pointed to polyphenols -- antioxidants contained in fruit juices -- suggesting they may disrupt the biological processes that lead to Alzheimer's. Antioxidants appear to neutralize the effect of free radicals, which attack healthy cells.

Alzheimer's disease is the most common cause of dementia among older people, according to the National Institutes of Health. It is marked by the progressive and irreversible decline of certain cognitive functions, including memory, time and space orientation, abstract thinking, the ability make mathematical calculations, language and communication skills, and the performance of routine tasks.

The United States will see a 44 percent increase in individuals with Alzheimer