Cacao and Mood: The Science of Chocolate

Note: this is a short launch draft. It's being expanded into a full piece, and every figure in it gets read back against the source before that happens.

Chocolate is the one polyphenol food people want to be good for them, so it collects more generous headlines than the evidence earns. I'll separate the two.

What's established

Cocoa flavanols, the polyphenols in cacao, have one effect that's been measured many times: a small drop in blood pressure. The 2017 Cochrane review of 35 trials found about 1.8 mmHg off systolic and diastolic pressure, more in people whose pressure was already high. That's a real result, it's modest, and it comes from doses higher than a typical bar supplies. I've written it up separately.

What's claimed

The mood and brain claims rest on a much thinner base. Cocoa contains small amounts of theobromine and caffeine, both mild stimulants, and some trials report better performance on attention tasks in the hours after a high-flavanol cocoa drink. Longer trials in older adults have looked at memory and processing speed with mixed results, and the ones that found effects used research-grade cocoa extracts, not chocolate.

The "chocolate makes you happy" finding is mostly about the experience of eating chocolate, which is real but isn't a polyphenol effect. Sugar, fat, and the fact that you like it do a lot of that work.

How to think about it

Dark chocolate with a high cocoa percentage is a reasonable thing to eat if you enjoy it. The higher the percentage, the more flavanols and the less sugar. Cocoa powder that hasn't been "Dutch processed" keeps more of its flavanols than alkalized cocoa does. Beyond that, I'd stop at "pleasant and probably a little good for your blood pressure". The brain story might turn out to be true. It hasn't yet.