Eating grapes daily can help protect the brain against early decline associated with Alzheimer's disease, show results of a pilot study involving people with early memory decline.
Alzheimer's disease is a brain disease that results in a slow decline of memory and cognitive skills.
"The study examines the impact of grapes as a whole fruit versus isolated compounds and the results suggest that regular intake of grapes may provide a protective effect against early decline associated with Alzheimer's disease," said lead investigator of the study Daniel Silverman from University of California Los Angeles, US.
"This pilot study contributes to the growing evidence that supports a beneficial role for grapes in neurologic and cardiovascular health, however more clinical studies with larger groups of subjects are needed to confirm the effects observed here," Silverman added.
The study results, published in Experimental Gerontology, showed a grape-enriched diet protected against the decline of metabolic activity.
Low metabolic activity in these areas of the brain is a hallmark of early stage Alzheimer's disease.
Additionally, those consuming a grape-enriched diet also exhibited increased metabolism in other areas of the brain that correlated with individual improvements in attention and working memory performance, compared to those on the non-grape diet.
In the study, participants with early memory decline were randomly selected to receive either whole grape powder -- equivalent to just a little over two cups of grapes per day -- or a polyphenol-free placebo powder matched for flavour and appearance.
Cognitive performance was measured at baseline and six months later. Changes in brain metabolism, assessed by brain scans, were also measured at baseline and six months later.
The results showed that consuming grapes preserved healthy metabolic activity in the regions of the brain that are affected by the earliest stages of Alzheimer's disease, where metabolic decline takes hold.
Participants who did not consume grapes exhibited significant metabolic decline in these critical regions.
Grape polyphenols help promote antioxidant and anti-inflammatory activities.
Previous research had shown that grapes may help support brain health by working in multiple ways - from reducing oxidative stress in the brain to promoting healthy blood flow in the brain to helping maintain levels of a key brain chemical that promotes memory to exerting anti-inflammatory effects.