Prospective randomized double-blinded longitudinal pilot study of effect of grapes on cerebral function.

Objectives Natural compounds in grapes such as resveratrol have known antioxidant and anti-inflammatory properties. Some studies have shown a potential role for grapes or wine in slowing cognitive decline. Effects of grapes on regional cerebral metabolism remain to be systematically assessed.

Methods A prospective, placebo-controlled, double-blinded design was employed. Subjects with mild decline in cognition were enrolled and provided informed consent and HIPAA releases (n=13). Assessment by neuropsychologic testing and FDG PET were obtained at baseline and again at 6-month follow-up. Subjects were randomized to consume an active grape formulation (lyophilized whole freeze-dried grapes, 36g PO BID, reconstituted in water) or a placebo formulation matched in appearance, volume, and content of fructose and glucose, but free of polyphenols. Longitudinal changes within each arm, and differences between randomized arms were statistically assessed.

Results Over the 6 months of the study, subjects in the placebo arm underwent significant decline in metabolism of right posterior medial temporal cortex (p=0.005), right posterior cingulate cortex (p=0.001) and left superior lateral cortex (p=0.04), while no significant decline in metabolism was observed for any region in the active formulation. In direct comparison of differences between randomized arms, right superior parietal cortex (p=0.03) and left inferior anterior temporal cortex (p=0.1) were the regions whose changes differed most significantly, as did the mean value of their changes (p=0.003). This mean change value correlated with improvements in neuropsychological performance in attention/working memory (WAIS-IIIDSp) within the active formulation group (p=0.04).

Conclusions In a double-blinded placebo-controlled longitudinal pilot study, twice daily consumption of table grapes was associated with significant alteration of longitudinal changes in cerebral metabolism, which in turn were correlated with improvements in attention/working memory performance.