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In 2010, the first controlled trial was published examining how the brain responds to grape juice. It helped aged rats, but what about people? Concord grape juice supplementation improves memory function in older adults with mild cognitive impairment, or so says the title. The problem is that the study was funded by Welch’s, and though the authors claim they have no financial interest in the outcome, that seems disingenuous. I mean, do they think Welch’s would ever fund them again if they found grape juice wasn’t good for you? And indeed, that title is a bit of industry spin. I’m sure that’s what they wanted to find.

Older adults with memory decline, but not dementia, were randomized into a placebo-controlled, double-blind trial with Concord grape juice versus a same calorie, same sugar, similarly looking/tasting grape-Kool-Aid type drink. So that’s a solid study design, and look, berries have those wonderful polyphenol phytonutrients, which have anti-inflammatory and antioxidant properties, so it certainly could help brain function and it did seem to help with verbal learning. The chances you’d get such notable results just by chance is like 1 in 25, whereas the higher recall scores are considered not statistically significant––since even if there wasn’t an effect, you might get those kinds of results by chance 1 in every 8 or 10 times you’d run the experiment. And by convention, we really like at least 1 in 20, so a p-value of 0.05 or less––especially if we’re looking at multiple outcomes, which increases the likelihood that something will pop up as a fluke. Bottom line is that we’re less confident in these memory outcomes, so I imagine if this hadn’t had industry funding, it would be titled more accurately: Concord grape juice supplementation improves verbal learning in older adults with mild cognitive impairment—which is still an important finding. And, we have the Welch’s corporation to thank for it. Without industry funding, a study like this might never get done.

The findings suggest that drinking grape juice is superior to drinking grape Kool-Aid, not necessarily for memory, but maybe for helping with learning. When the study was repeated, though, it did seem to help one measure of memory, but found no benefit for verbal learning––even when using the exact same test as before, which calls the previous results into question. So, we’re left uncertain about what effects, if any, grape juice has on the aging brain.

What about the brains of middle-aged mothers? The Welch’s-funded researchers noted significant improvements in one measure of memory and driving performance, as measured in some fancy driving simulator, suggesting on grape juice you might be able to stop a dozen yards earlier on the highway than if you had instead been drinking grape Kool-Aid. I do like how they tried to translate the cognitive effects into more meaningful metrics, but it’s important to acknowledge, as they did, that no effects were found for the majority of cognitive consequences. And when you study 20 different outcomes, the odds are pretty good that you’d just get a statistically significant result or two by chance.

The latest study involved a single dose given to young adults, average age 21: a cup of purple grape juice or white grape juice to which flavor and color had been added to disguise it. In this way, we could see if there’s something special about those deep purple polyphenol pigments in concord grape juice, and, got the same kind of results: two cognitive measures just achieving statistical significance. But that’s out of seven different outcomes. So instead of 0.05 as the cut-off for significance, we’d really like to see closer to 0.007, and none hit that. Maybe it’s because they didn’t use the whole food, like in that blueberry study I profiled before.

There was a study that looked at actual grape consumption, by utilizing freeze-dried grape powder to capture the whole food instead of just the juice, versus a sugar-matched placebo. They used PET scans to track changes in brain metabolism associated with early Alzheimer’s in a group of older adults already suffering from mild cognitive decline. Although the changes couldn’t be picked up on neuropsych testing, in those early-stage Alzheimer regions, the placebo group continued to worsen, but the grape group was spared such decline, suggesting a protective effect of grapes. Here that is in graph form, showing the significant difference, or even better, brain mapping pictures. Here’s one of the placebo brains. The red areas indicate locations where brain metabolism declined after eating six months of placebo grapes. Compare that level of decline to a brain that ate six months of actual grapes.

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