Cocoa powder is derived from the cocoa bean, which is the seed of cacao tree (Theobroma cacao), a plant that is indigenous to the Americas’ equatorial regions. Cacao is minimally processed, whereas cocoa has been further processed (roasted, alkalized) for palatability.^[8][1]

Cocoa is a rich source of antioxidants and has a higher flavonoid concentration and total antioxidant capacity than other flavonoid-containing sources such as red wine, green tea, and black tea.^[30][31][17]

A large body of evidence shows that cocoa has small and somewhat consistent benefits in cardiovascular disease, in which it benefits certain outcomes such as blood pressure, HOMA-IR, and LDL-C.^{[2][1][3][5][8][27][25][28]}

Beyond cardiovascular disease, the benefits of cocoa are much less consistent. For example, the benefits of cocoa on cognitive function in older adults are inconsistent.^[32][33] In exercise, although cocoa likely increases nitric oxide, cocoa did not improve exercise time-trial performance and time to exhaustion (though the results were of borderline statistical significance) in a 2021 meta-analysis of 4 randomized controlled trials.^[34]

Seven meta-analyses of randomized controlled trials (RCTs) examined adverse events from consumption of cocoa or chocolate, but the researchers did not find an increase in adverse events.^{[2][5][17][8][27][25][28]}

The variable sugar, saturated fat, and calorie content of chocolate could be drawbacks. For instance, a bar of dark chocolate that weighs 100 grams can contain approximately 500 calories, which can lead to an excess consumption of calories and weight gain. However, large meta-analysis of RCTs have shown no negative effects of cocoa on markers of anthropometrics (e.g., body weight, BMI, and waist circumference), glycemic control, or blood lipids.^[2] In fact, cocoa is often associated with beneficial effects on various markers of glycemic control or blood lipids.^{[2][5][17][8][27][25][28]} Furthermore, in a 2019 meta-analysis of 35 RCTs, there was no overall effect of cocoa on anthropometrics, but in subgroup analyses, there were reductions in body weight and BMI at cocoa/dark chocolate doses that exceeded a dosage of 30 grams per day and for durations of more than 4 weeks.^[26]

In pregnancy, polyphenol consumption that exceeded 125 mg per day might increase fetal complications.^[20][21][22] Cocoa is a source of polyphenols, but the density varies. In one study, 10 grams (0.35 oz; 1 square in some chocolate bars) of 99% dark chocolate contained 65 mg of polyphenols,^[23], but in another study, 10 grams of 83% dark chocolate contained 180 mg of polyphenols.^[24] Therefore, consumption of cocoa in pregnancy is cautioned.

Ingestion of chocolate can provoke migraine headaches in some people.^[35][36][37] In particular, chocolate was one of the most common food triggers for migraine in one cross-sectional study.^[38] However, the research on cocoa and migraines is inconsistent, as one cohort study showed that common migraine triggers such as caffeine and chocolate were associated with a reduced risk of migraine.^[39]

A majority of studies have found that the heavy metal content of chocolate was within the acceptable limits in a variety of countries.^{[40][41][42][43][44][45][46][47][48][49]} A few studies have reported heavy metals at levels that exceeded the acceptable limits in a minority of the cocoa products examined.^[50][51][52]

Plants such as the cacao tree (which is the source of cocoa) produce various flavonoids (a type of polyphenol) as byproducts of their metabolism. In these plants, flavonoids have roles in pigmentation, flavor, growth, reproduction, and pathogen resistance.^[53][4] In humans, the flavonoids in cocoa likely increase the activation of nitric oxide (NO) and exert antioxidant and anti-inflammatory effects. These mechanisms potentially explain how cocoa improves endothelial function, reduces platelet aggregation and blood pressure, and improves glycemic control and blood lipids.^{[54][2][17][25][1]}

Specifically, cocoa may lower the activity of enzymes that break down arginine, thereby increasing the conversion of arginine to NO. Nitric oxide can cause a relaxation of the smooth muscle in blood vessels, thereby decreasing blood pressure, and NO can also decrease the aggregation of platelets, which reduces the formation of blood clots.^{[55][56][57][54][58][8]} This increased blood flow might be how cocoa exerts cognitive benefits (though this benefit seems unlikely).^[59][60] In addition, cocoa’s polyphenols have antioxidant effects that reduce inflammatory factors. These polyphenols may also inhibit angiotensin-converting enzymes (ACE), thereby decreasing blood pressure.^{[61][54][62][2][25][1]} Cocoa also contains other active substances, such as magnesium, potassium, and theobromine, all of which may have their own effects on lowering blood pressure.^{[25][54][63][64]}

Despite its sugar content, chocolate may decrease insulin resistance via NO because insulin sensitivity is partly dependent on insulin-mediated NO release. Furthermore, dark chocolate can improve beta-cell function (i.e., insulin secretion).^[65][66][54] Additionally, there are various hypotheses as to why cocoa might have beneficial effects on glycemic control, and many of them center around slowing the digestion and absorption of carbohydrates in the intestinal tract, increasing glucose metabolism, and reducing glucose synthesis.^[5][8]

Cocoa might have beneficial effects on blood lipids due to its fatty acid composition, even though much of the fat (butter) has been removed in cocoa powder. Cocoa butter is composed of 33% monounsaturated fat and 33% of the saturated fat stearic acid, and stearic acid may have a beneficial effect on blood lipids.^[67][54][8] The procyanidins (another class of flavonoids) in chocolate may also inhibit the absorption of cholesterol and reduce the expression of LDL-C receptors.^[68][69][70] In addition, cocoa might reduce cholesterol synthesis, reduce lipid synthesis, and increase lipid metabolism.^[8][71][72]