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Is dark chocolate good for your heart?

What you hear: “Dark chocolate is a superfood that protects your heart, so eating it daily is good for you.”

What the studies found

A Cochrane review of 35 trials (about 1,800 mostly healthy people, 2 to 18 weeks) found flavanol-rich cocoa lowered blood pressure by under 2 mmHg on average, a small effect. The large COSMOS trial gave 21,442 older adults a cocoa extract supplement or placebo for a median 3.6 years and found no significant drop in total heart events, though deaths from heart disease were 27% lower, a secondary finding. That trial used a concentrated capsule, not chocolate bars, which also bring sugar, fat and calories. In 2022 testing of 28 dark chocolate bars, Consumer Reports found lead and cadmium in all of them, and 23 would put an adult over its chosen safety level at one ounce a day.

Take care: Heavy metals in dark chocolate are of most concern for pregnant people and young children; chocolate is also calorie-dense.

What you could do

Enjoy a small square of dark chocolate as a treat, vary brands, and don't count on it to protect your heart.

See it in the habit library, with what it means for your own longevity score.

Not medical advice. General information from published studies, not a diagnosis or a treatment plan. Talk with your doctor before starting a supplement or changing a medicine, especially if you are pregnant, take other medicines or have a health condition.

How we judged it

Partly true: Some truth, but oversold as usually said. We judge the claim as it is usually said online, not the habit itself. Trials assign people at random, so they can show cause; observed studies follow people and show a link, not proof. Last checked: October 2026.

The studies, in their own words

1. Ried et al. Cochrane Database Syst Rev 2017

   Mean difference systolic blood pressure (SBP) (95% confidence interval (CI): -1.76 (-3.09 to -0.43) mmHg, P = 0.009, n = 40 treatment comparisons, 1804 participants

2. Sesso et al. Am J Clin Nutr 2022 (COSMOS)

   During a median follow-up of 3.6 y, 410 participants taking cocoa extract and 456 taking placebo had confirmed total cardiovascular events (HR: 0.90; 95% CI: 0.78, 1.02; P = 0.11).

3. Sesso et al. Am J Clin Nutr 2022 (COSMOS)

   Cocoa extract supplementation did not significantly reduce total cardiovascular events among older adults but reduced CVD death by 27%.

4. Consumer Reports 2022/2023

   For 23 of the bars, eating just an ounce a day would put an adult over a level that public health authorities and CR’s experts say may be harmful for at least one of those heavy metals.

5. Consumer Reports 2022/2023

   The danger is greatest for pregnant people and young children because the metals can cause developmental problems

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