Cocoa and dark chocolate: what the evidence says about blood pressure and the brain

Cocoa beans are the fermented, dried seeds of the cacao tree. Ground and partly defatted, they become cocoa powder; mixed with cocoa butter and sugar, they become chocolate. The compounds researchers care about are flavanols (mainly epicatechin and its relatives), and processing changes how much survives. The trials on this page mostly used specially made high-flavanol cocoa drinks, bars or capsules, so their doses are not the same as a square of a supermarket bar.

Cocoa also brings two stimulants. USDA lists unsweetened cocoa powder at about 230 mg of caffeine and 2,057 mg of theobromine per 100 grams, and 70 to 85% dark chocolate at about 80 mg of caffeine and 802 mg of theobromine per 100 grams USDA; USDA. A tablespoon or two of cocoa powder in a drink is therefore a modest caffeine source, well below FDA's 400 mg a day figure for most adultsFDA.

The 2017 Cochrane review pooled 35 randomized trials that gave people 30 to 1,218 mg of flavanols a day (in 1.4 to 105 grams of cocoa products) for at least two weeks. Compared with flavanol-free or low-flavanol products, cocoa lowered systolic and diastolic blood pressure by about 1.8 mmHg each Ried 2017. The reviewers rated this moderate-quality evidence and pointed out several limits: the results varied between trials in ways they could not explain, unblinded trials tended to show larger effects, and leaving out trials with industry-employed authors shrank the effect a little Ried 2017.

In people with high blood pressure, systolic pressure fell by about 4 mmHg, while in people with normal pressure there was no significant change; the test for that difference was borderline, so it is a lead rather than a finding Ried 2017. Either way, a couple of points is a modest change, well short of what a blood pressure medicine does. Cocoa is not a reason to change or stop a prescription.

COSMOS was the first large test of whether cocoa flavanols change hard outcomes. It randomly assigned 21,442 US adults (women 65 and older, men 60 and older) to a cocoa extract capsule providing 500 mg flavanols a day, including 80 mg epicatechin, or placebo. After a median of 3.6 years, 410 people on cocoa extract and 456 on placebo had a cardiovascular event, a difference that was not statistically significant Sesso 2022. Death from cardiovascular causes, a secondary outcome, was 27% lower in the cocoa group, and an analysis limited to people who kept taking their pills also favored cocoa. The authors concluded that more research is needed Sesso 2022.

Two COSMOS sub-studies looked at the brain. COSMOS-Mind followed 2,262 adults with a mean age of 73 for three years and found that cocoa extract had no effect on global cognition Baker 2023. COSMOS-Web tested memory online in 3,562 older adults; the main one-year result was not significant, but memory improved among people whose usual diet was lower in quality or in flavanols Brickman 2023. That pattern fits the idea that flavanols matter most when a diet lacks them, but it comes from a subgroup, and the study was funded in part by a chocolate maker Brickman 2023.

Smaller trials of regular cocoa or dark chocolate in a 2026 meta-analysis showed modest gains on some timed tests of attention and processing speed, mostly at 500 mg flavanols a day or more for eight weeks or longerArabpour 2026. That is a sign worth following, not a reason to eat chocolate for focus.

Labels rarely state flavanol content, and alkalized ("Dutch-processed") cocoa generally keeps less of it, so the trial doses cannot be matched reliably from a supermarket shelf. A reasonable kitchen approach is plain unsweetened cocoa in place of sweeter snacks, rather than extra chocolate on top of the usual diet.

Unsweetened cocoa powder is easy to find in grocery stores; online, iHerb lists unsweetened cocoa powders if you want to compare products.

Cacao can pick up lead and cadmium from soil and processing. A study of 72 US cocoa products bought between 2014 and 2022 found that 43% exceeded California's strict Prop 65 daily limit for lead and 35% for cadmium per serving, while 97% were below FDA's interim reference level for lead Hands 2024. Median levels were below even the Prop 65 limits; the authors judged that a single serving of most products was unlikely to pose an appreciable risk, but that several servings a day, or certain products, could add up. Products labeled organic were more likely to have higher lead and cadmium Hands 2024. Varying brands and keeping portions moderate are sensible, especially for children and during pregnancy.