However, it doesn't prove that the juices can definitely help dodge Alzheimer's, the most common form of mental decline in older adults. Scientists do not yet have iron-clad recommendations to prevent Alzheimer's.
The finding was presented in Washington, at the Alzheimer's Association International Conference on Prevention of Dementia. The researchers included Amy Borenstein, PhD, MPH, an epidemiology professor at the University of South Florida.
"These findings suggest that something as simple as incorporating more fruit and vegetable juices into our diet may have a significant impact on our brain health," says Borenstein, in a news release.
The results came from the Kame Project, a long-term study of more than 1,800 Japanese- Americans in the Seattle area. When the study started in 1992-1994, no participants had dementia. They were about 71 years old, on average.
At the beginning of the study, participants completed surveys about the foods and drinks they typically consumed. Smoking, alcohol, daily calories, physical activity, body mass index (BMI), vitamin supplements, and other health problems (such as diabetes and cancer) were also noted.
Food Survey Results
The group was followed through 2001. During that time, 81 cases of probable Alzheimer's disease were diagnosed in participants who had completed the food surveys.
The most frequent juice drinkers were the least likely to have developed Alzheimer's. Those who reported drinking fruit or vegetable juices at least three times per week were 73% less likely to have developed Alzheimer's as those who drank juice less than once a week.
Those who drank juice once or twice a week also had a possible advantage, but the effect wasn't strong enough to know for sure.
"Certain polyphenols abundant in fruit and vegetable juices may play an important role in delaying Alzheimer's onset," say Borenstein and colleagues.
Animal studies have found that a number of polyphenols from juices may protect brain cells against oxidation more than vitamin E and C, say the researchers. "These results may lead to a new avenue of inquiry in the prevention of Alzheimer's disease," they write.
Borenstein and colleagues did not report any ties to commercial interests (such as juice companies). No particular juices were singled out. Juices were not directly tested for any health benefits. It's always possible that self-reported food surveys may be inaccurate, or that participants' habits changed over time.