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Dark Chocolate and Cocoa for Blood Pressure: What the Evidence Shows

Can dark chocolate or cocoa lower blood pressure? Learn what a Cochrane review and a large trial found, how much people use, and the downsides to weigh.

Edited by Anmar ArabPublished 23 October 2026, 7 min read
On this page
  1. Quick answer
  2. What the research says
  3. How to use it
  4. Possible side effects and interactions
  5. Who should be careful
  6. When to see a doctor
  7. Frequently asked questions

Quick answer

Cocoa beans are rich in plant compounds called flavanols, which is why dark chocolate and cocoa are often described as heart-friendly.

  • There is a small, real effect on blood pressure. A Cochrane review of 35 trials found that flavanol-rich cocoa products lowered blood pressure by about 2 mmHg on average over a few weeks.
  • The effect looks larger in people with high blood pressure, at roughly 4 mmHg for the top (systolic) number, and was not significant in people with normal blood pressure.
  • Chocolate is not a treatment. The effect is small and the studies lasted only weeks.
  • A large trial of a cocoa extract supplement, not chocolate, did not significantly reduce overall heart attacks and strokes, although deaths from cardiovascular causes were lower.
  • Watch the extras. Chocolate brings sugar, fat and calories, a little caffeine, and some bars contain measurable lead and cadmium.

What the research says

The Cochrane review (2017). Ried and colleagues pooled 35 randomised trials covering 40 comparisons and 1,804 mostly healthy adults. Participants had flavanol-rich chocolate or cocoa for 2 to 18 weeks (about 9 weeks on average). Compared with a low-flavanol or flavanol-free control:

  • systolic blood pressure (the top number) fell by an average of 1.76 mmHg
  • diastolic blood pressure (the bottom number) also fell by an average of 1.76 mmHg

When the reviewers split people by their starting blood pressure, those with high blood pressure saw a drop of about 4 mmHg in systolic pressure. People with slightly raised blood pressure showed a trend towards lower readings that was not statistically significant, and people with normal blood pressure showed no significant change. The reviewers rated the overall evidence as moderate quality, mainly because results varied a lot between trials. They also found that the effect shrank when trials with authors linked to industry were left out, which hints at some reporting bias. Their conclusion was that flavanol-rich cocoa has a small blood pressure-lowering effect in the short term, and that longer trials are needed.

The EFSA opinion. The European Food Safety Authority (EFSA) assessed cocoa flavanols and accepted a narrower claim: that they help maintain the normal widening of blood vessels, which supports normal blood flow. EFSA said this needs 200 mg of cocoa flavanols a day, which could come from 2.5 g of high-flavanol cocoa powder or 10 g of high-flavanol dark chocolate. This claim is about blood vessel function, not about treating high blood pressure.

The COSMOS trial. This large US trial gave 21,442 older adults either a daily cocoa extract supplement or a placebo, for a median of 3.6 years. According to a summary from Brigham and Women's Hospital, the supplement did not significantly reduce total cardiovascular events such as heart attacks and strokes. Deaths from cardiovascular causes were 27% lower in the cocoa group, a promising secondary finding that needs confirming. The trial used capsules, not chocolate, so its results cannot be assumed to apply to eating chocolate.

What this means in practice. The Cochrane authors describe an average drop of about 2 mmHg as small, and the trials did not look at long-term outcomes such as heart attacks or strokes. Cocoa may be a small, pleasant addition to a healthy diet, but it is not a substitute for proven approaches.

How to use it

If you enjoy chocolate and want to choose it with heart health in mind:

  • Think small amounts. The EFSA assessment linked the vessel-function effect to about 10 g of high-flavanol dark chocolate or 2.5 g of high-flavanol cocoa powder a day.
  • Swap rather than add. Use dark chocolate in place of other sweet snacks, not on top of them, to avoid adding calories and sugar.
  • Look for stated flavanol content where possible. Most chocolate does not list flavanols, so the word "dark" alone does not tell you how much you are getting.
  • Consider unsweetened cocoa powder stirred into milk, yoghurt or porridge.
  • Pick brands that tested lower for heavy metals, or keep chocolate occasional, as Harvard Health suggests (see below).

Keep taking any prescribed medicine exactly as directed.

Safety note: Chocolate or cocoa is not a replacement for blood pressure medicine. Never stop or reduce a prescribed treatment without speaking to your doctor first.

Possible side effects and interactions

Digestive upset. In the Cochrane review, side effects were generally mild. Stomach complaints and nausea were reported by about 1% of people eating cocoa products, compared with 0.4% of controls. In COSMOS, nausea was more common in the cocoa extract group.

Sugar, fat and calories. Even dark chocolate is energy-dense, and regular large portions can work against weight and blood sugar goals.

Caffeine. MedlinePlus lists dark chocolate at about 10 mg of caffeine per ounce (28 g) and unsweetened baking chocolate at about 58 mg per ounce. This is modest, but it adds to caffeine from other sources.

Lead and cadmium. In a 2022 Consumer Reports test described by Harvard Health Publishing, 23 of 28 dark chocolate bars would have exceeded a California safety limit for lead, cadmium or both if a person ate one ounce a day. Long-term exposure to these metals is linked to health problems, including heart disease. Harvard suggests choosing brands that tested lower or eating dark chocolate only occasionally.

Interactions. MedlinePlus notes that many medicines interact with caffeine. If you take regular medicines and plan to eat large amounts of chocolate or cocoa, ask a pharmacist whether this matters for you.

Who should be careful

  • People with high blood pressure that is not controlled by medicine, or with a fast or irregular heartbeat, are among those MedlinePlus advises to limit caffeine.
  • People with acid reflux or stomach ulcers, who may also be advised to limit caffeine.
  • Pregnant women, who are advised to keep total caffeine under 200 mg a day.
  • Children, for whom there are no caffeine guidelines; the American Academy of Pediatrics discourages caffeine for them.
  • People managing diabetes or their weight, because of the sugar and calories.
  • People with anxiety or sleep problems, whom MedlinePlus lists among those who may need to limit caffeine.

When to see a doctor

Have your blood pressure checked regularly rather than relying on how you feel. See a doctor if your home or pharmacy readings are repeatedly above the target you have been given, or if you have never had your blood pressure measured.

Seek emergency help immediately if your blood pressure is 180/120 mmHg or higher and you have any of the following:

  • chest pain
  • shortness of breath
  • numbness, tingling or loss of feeling in the face, arm or leg, often on one side
  • trouble speaking or walking
  • changes in vision

Other warning signs with a very high reading include a severe headache, confusion, blurred vision, nausea and vomiting, or a seizure. If you have a very high reading without symptoms, rest for a few minutes and check again; if it is still very high, get medical care promptly.

Frequently asked questions

How much dark chocolate should I eat for blood pressure?

There is no recommended dose for lowering blood pressure. EFSA linked a blood vessel benefit to 200 mg of cocoa flavanols a day, which it said could come from about 10 g of high-flavanol dark chocolate. Most chocolate does not state its flavanol content, so if you enjoy it, keep portions small and treat it as part of a balanced diet rather than as a remedy.

Can cocoa replace my blood pressure tablets?

No. The average effect in trials was small, about 2 mmHg, and the studies lasted only weeks. Keep taking your medicine as prescribed and talk to your doctor before making any change.

Are cocoa flavanol supplements better than chocolate?

Supplements can provide more flavanols without the sugar and fat. However, the large COSMOS trial did not show a significant reduction in overall heart attacks and strokes, so supplements are not proven to prevent heart disease. Discuss them with your doctor or pharmacist first, especially if you take other medicines.

References

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