Polyphenols are plant-derived compounds found in foods like grapes, apples, blueberries, green tea, and cocoa, and have gained a lot of popularity due to their antioxidant action. Antioxidants fight free radicals, which can do major damage to all the cells in our bodies and to our DNA.

Previous work has suggested that the polyphenols in grapes may be linked to reduced risk for cognitive decline. The current study shows how the mechanism behind this phenomenon may actually work: by reducing levels of the dangerous amyloid-beta (Aβ) peptides that are high in the brains of Alzheimer’s patients.

'Since naturally occurring polyphenols …have negligible adverse events even after prolonged periods of treatment, this new finding holds significant promise as a preventive method or treatment, and is being tested…in Alzheimer's disease patients.'

For five months, the researchers gave grape seed polyphenol extract to mice who were genetically engineered to develop Alzheimer’s disease with high levels of Aβ "neurotoxins." After this time, they compared levels of Aβ peptide in the brains of mice who had received the extract to those who had not. The mice who had gotten the grape seed extract had significantly reduced levels of one type of peptide, Aβ*56, compared to controls.

Author Giulio Maria Pasinetti says the findings can likely be applied to humans: "Since naturally occurring polyphenols are also generally commercially available as nutritional supplements and have negligible adverse events even after prolonged periods of treatment, this new finding holds significant promise as a preventive method or treatment, and is being tested…in Alzheimer's disease patients."

However, finding a biomarker to help researchers predict who is more likely to develop Alzheimer’s will also be necessary: "It will be critical to identify subjects who are at high risk of developing Alzheimer's disease, so that we can initiate treatments very early and possibly even in asymptomatic patients," said Pasinetti.

It is unclear whether the treatment may be used in patients who already have the disease, but the team is hopeful that it will. While researchers are exploring the role of grape seed polyphenols in Alzheimer’s prevention, it probably won’t hurt to add a few red grapes to your diet or have a glass of red wine every now and again.

The study was carried out by researchers at the Mount Sinai School of Medicine, and published online in the July 15, 2011 issue of the Journal of Alzheimer's Disease.