Many animals, especially dogs and cats, cannot tolerate theobromine which is an alkaloid from the cacao plant. Studies of humans, however, have found many beneficial health effects of theobromine, caffeine as well as flavonoids found in cocoa (Martinez-Pinilla et al., 2015).
A new study published in Journal of Applied Physiology examined whether cocoa extract can improve heart health in individuals exercising in hypoxic conditions. Hypoxia (i.e. low atmospheric oxygen) reduces the amount of oxygen that can be delivered to the brain and muscle tissues. In this study, trained male cyclists (average 30 years old) were instructed to consume cocoa extract (containing 100 mg epicatechin, 23 mg catechin, 119 mg theobromine, 17 mg caffeine) or a placebo for 7 days. The researchers found that simply consuming cocoa extract for 7 days improved blood vessel function, which they measured by determining how well blood vessels dilate in response to changes in blood flow (i.e. flow-mediated vasodilation). Under hypoxic conditions (mimicking 3000 meters, 14.3% oxygen), oxidative stress resulting from exercise increases and oxygen delivery to the brain and muscles decreases. Interestingly, at both rest and following exercise, cocoa extract helped improve oxygen delivery to the brain, but not the muscles. In addition, cocoa extract helped reduce exercise-induced oxidative stress under hypoxic conditions although it did not improve exercise performance.
Martinez-Pinilla E, Onatibia-Astibia A, Franco R. The relevance of theobromine for the beneficial effects of cocoa consumption. Frontiers in Pharmacology. 6:30, 2015. doi: 10.3389/fphar.2015.00030