Everyone knows that aerobic exercise is good for the body, but is it always as good for the brain?  And more to the point, is it any better than eating lots of chocolate?

For a recent study published in the prestigious journal Nature Neuroscience, a group of researchers from Columbia University and NYU gave a large daily dose of flavanols extracted from cocoa powder to a small number of 50-to-69-year-old year old subjects who then reported improved memory and enhanced blood flow in a part of the brain, the hippocampus, that is responsible for memory formation. Notably, the team had half of their healthy, but sedentary subjects take part in a four-days-per-week exercise program, but found that the workouts had no beneficial effects on memory or cognition.

The headlines read, "To Improve a Memory, Consider Chocolate."

But if this sounds too good to be true, it probably because it is.

Two things about this study tend to undermine my confidence in its results: First, that the older people reportedly did not appear to benefit at all from exercising. This finding is not only inconsistent with the broad literature on this topic but was also a surprising failure by these scientists to replicate their own previous findings. Second, cocoa flavanols have been extensively investigated in both humans and animals and consistently found to produce no significant health benefits. Both the FDA and European Food Safety Authority have refused to approve any health claims made about these chemicals.

Chocolate is an excellent example of how difficult it is to differentiate food from drug. The cocoa powder used to produce chocolate is in fact rich in flavanols—and many other potentially psychoactive chemicals. Although the amount and types of flavanols depend on how the cocoa powder was processed and manufactured, a given powder may contain up to 10% its weight in flavanols. Overall, chocolate is not a great source of these flavanols. While expensive dark chocolate may contain anywhere from 45-80% cocoa powder, the chocolate found in the average candy bar has only about five to seven percent cocoa powder.

And how much chocolate would a person need to eat in order to achieve the results reported in this study? The subjects consumed a specially prepared commercial product that contained about one gram of flavanols, every day, for three months; 100 grams of standard cocoa powder, on the other hand, typically contains about 100 milligrams of flavanols. 

These values suggest that you might need to eat about one kilogram of pure unrefined cocoa powder—or about 44 pounds of chocolate candy every day. (Other, lower estimates suggest a minimum of seven full-size pure dark chocolate bars.) Therefore, in spite of the significant hype surrounding this report in the popular press, I would not recommend that anyone attempt to replicate this study at home. (Also, I should mention that flavanols are also found in many fruits and vegetables.)

Which leads me to the next most important question to answer: Is chocolate better than marijuana for the aging brain? My money is on cannabis-enriched chocolate bars. . .

© Gary L. Wenk, Ph.D., author of Your Brain on Food, 2nd Ed. 2014 (Oxford University Press)

TED talk on Healthy brain aging.

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