The likelihood that a person develops high blood pressure (hypertension) increases continuously with age.^[1] This is noteworthy because hypertension is well established as playing a causal role in the development of cardiovascular disease (CVD).

A large number of studies looking at the effect of cocoa on blood pressure have been conducted, with a 2017 meta-analysis noting that cocoa leads to a small reduction in blood pressure.^[3] Observational evidence has also found that eating a moderate amount of chocolate is associated with a lower risk of cardiovascular disease.^[4] However, there has yet to be any clinical trial examining the effect of cocoa on cardiovascular disease outcomes.

This randomized controlled trial examined the effect of cocoa extract on CVD events among 21,442 people (mean age of 72) without previous cardiovascular disease or cancer. The participants were assigned to take a supplement containing cocoa extract or a placebo daily. The cocoa extract supplement provided a daily dosage of 500 mg of flavanols (also known as flavan-3-ols), 80 mg of which were the subtype (–)-epicatechin, as well as roughly 50 mg of theobromine and 15 mg of caffeine.

The primary outcome was a composite of total CVD events, which included myocardial infarction, stroke, coronary revascularization, cardiovascular mortality, carotid artery surgery, peripheral artery surgery, and unstable angina requiring hospitalization. The latter three events were added after the start of the study due to lower than anticipated rates of CVD events. The secondary outcomes included CVD mortality, a combination of CVD events and all-cause mortality, each of the individual CVD events, and the original composite of CVD events (without the three that were added later). Other secondary outcomes included invasive cancer (excluding melanoma), breast cancer, colorectal cancer, and lung cancer. The median follow-up period was 3.6 years.

Cocoa extract reduced the incidence of CVD mortality (a secondary outcome) by 27% (absolute risk reduction of 0.07%), major CVD events (an unplanned outcome measure) by 16% (absolute risk reduction of 0.12%), and had no effect on total cardiovascular events (the primary outcome). Other outcomes were not significantly different between groups.

Incidence of CVD mortality between groups

This study received funding from Mars, a chocolate company.

This trial provides some evidence that cocoa extract can reduce the risk of dying from cardiovascular disease. Still, this is currently the only randomized controlled trial looking at such an outcome, and there are important points to consider about its findings. The fact that CVD mortality was decreased, while total CVD events — the primary outcome — were not, is somewhat concerning. On the other hand, it’s possible that the very low rates of total CVD events in this trial (1.08% in the cocoa group and 1.2% in the placebo group) meant that it was underpowered to detect significant differences between groups. Additionally, it’s possible that cocoa primarily affects the more life-threatening types of CVD events.

The mechanism behind cocoa’s potential cardiovascular benefits are not known with certainty. Several studies suggest that cocoa supplementation can increase nitric oxide levels.^[5][6][7] Nitric oxide has a number of beneficial effects on the vascular system, most notably inducing vasodilation, which perhaps explains why cocoa has been found to lower blood pressure and improve markers of vascular function.^[8] Exactly how cocoa increases nitric oxide levels is hard to say, but some in vitro research suggests it could be at least partly the result of (–)-epicatechin increasing the activity of endothelial nitric oxide synthase (eNOS), an enzyme that synthesizes nitric oxide.^[9][10][11]

The most biologically active component of cocoa is generally believed to be (–)-epicatechin. This study delivered 80 mg of (–)-epicatechin via a supplement. As seen in the table below, getting 80 mg of epicatechin from any one food would be difficult, but may be more feasible if a variety of the food sources are incorporated into the diet. For example, eating 1 ounce of dark chocolate, 2 medium-sized apples, 6 ounces of blackberries, and drinking 1 cup (8 ounces) of green tea would provide about 80 mg of (–)-epicatechin.

Common food sources of (–)-epicatechin

Food source	(–)-Epicatechin per 100 grams/mL of food	Amount of food needed to obtain 80 mg of (–)-epicatechin	Notes
Cocoa powder	158 to 196 mg	40 to 50 grams	(–)-Epicatechin content lower in alkalized cocoa
Dark chocolate	71 to 84 mg	95 to 113 grams	—
Milk chocolate	10.9 to 14.6 mg	548 to 800 grams	—
Red wine	3.8 mg	2.18 liters (74 ounces)	—
Red wine (Cabernet Sauvignon)	10.7 mg	0.75 liters (26.5 ounces)	—
Green tea	8.3 mg	0.96 liters (32 ounces)	—
Black tea	2.1 mg	3.76 liters (127 ounces)	—
Apple (Fuji)	5.7 mg	1.4 kg (3.1 pounds)	Higher amounts in skin than flesh
Blackberries	11.5 mg	0.7 kg (24.6 ounces)	—

References: Bhagwat and Haytowitz. 2016 https://doi.org/10.15482/USDA.ADC/1324465 | Neveu et al. 2010 Database, doi: 10.1093/database/bap024http://phenol-explorer.eu