The largest US-wide clinical trial to study high-dose resveratrol long-term in people with mild to moderate Alzheimer's disease has found that a biomarker that declines when the disease progresses was stabilized in people who took the purified form of resveratrol, which is a naturally occurring compound found in foods like red grapes, raspberries, dark chocolate and some red wines.
Principal investigator R Scott Turner said that the results are very interesting, but cautioned that the findings cannot be used to recommend resveratrol as it is a single study with findings that call for further research to interpret properly.
In the study, patients who were treated with increasing doses of resveratrol over 12 months showed little or no change in amyloid-beta40 (Abeta40) levels in blood and cerebrospinal fluid.
In contrast, those taking a placebo had a decrease in the levels of Abeta40 compared with their levels at the beginning of the study.
A decrease in Abeta40 is seen as dementia worsens and Alzheimer's disease progresses; still, researchers can't conclude from this study that the effects of resveratrol treatment are beneficial, Turner explains.
He added that it does appear that resveratrol was able to penetrate the blood brain barrier, which is an important observation. Resveratrol was measured in both blood and cerebrospinal fluid.
Turner says the study also found that resveratrol was safe and well tolerated. The most common side effects experienced by participants were gastrointestinal-related, including nausea and diarrhea. Also, patients taking resveratrol experienced weight loss while those on placebo gained weight.
One outcome in particular was confounding, Turner notes.
The researchers obtained brain MRI scans on participants before and after the study, and found that resveratrol-treated patients lost more brain volume than the placebo-treated group.
The study is published online in Neurology.