How cacao helps heart and blood vessels function better
More endurance athletes than you'd think use phenol-rich cacao as an effective performance enhancer. A Japanese animal study, published recently in PLoS One, shows how cacao works. The flavan-3-ols in cacao boost the activity of nitrogen monoxide or NO in the blood vessels, and as a result improve the blood's ability to transport oxygen and nutrients to the muscles. The ergogenic effect of cacao probably reaches its maximum 1-2 hours after intake.


Cacao is an NO-booster. If you give people a couple of grams of phenol-rich cacao every day their blood pressure goes down. The phenols in cacao boost the synthesis of NO in the blood vessels, as a result of which the vessels become wider and more supple. Researchers at the Shibaura Institute of Technology in Japan attempted to work out exactly how cacao phenols do this by performing experiments on rats.The Japanese gave the rats 10 mg cacao-derived flavan-3-ols per kg or ordinary water with no active ingredients. The most important flavonoid compounds in the extract were (+)-catechin and (-)-epicatechin. The human equivalent of this dose is about 100-150 mg.

Red blood cells
After intake, the number of red blood cells circulating in the capillaries started to increase, and an hour after intake the blood flow was still increasing.

The cacao phenols activated the enzyme that separates NO from L-arginine, the researchers observed 60 minutes after administration. At that point the concentration of nitrate and nitrite had increased: a sign of increased NO synthesis.

Almost immediately after the cacao phenols had entered the bloodstream the lab animals' heart rate and blood pressure rose, and the effect was sustained for about one hour.

The researchers believe that in this way the phenols imitate the effect of physical exertion. If the heart pumps blood through the arteries intensively for a short period, the blood vessel walls react by producing more NO.
And so...
The performance-enhancing effect of cacao is probably optimal if athletes ingest it 1-2 hours before a training session or competition. Once an hour has passed blood pressure and heart rate return to normal but the cardiovascular system is ready for physical exertion. The extra supple blood vessels are capable of transporting more oxygen and nutrients to the muscles and removing more waste products. In addition, supple blood vessels reduce the burden on the heart muscle.

PLoS One. 2014 Apr 16;9(4):e94853.