Seven meta-analyses of randomized controlled trials (RCTs) have examined the effects of cocoa (compared to placebo or white chocolate as a control) on cardiovascular health and found somewhat consistent small benefits of cocoa on blood pressure, glycemic control (e.g., HOMA-IR), and blood lipids (e.g., LDL-C).[1][2][3][4][5][6] For example, a 2024 meta-analysis of 31 RCTs and 1,986 total participants reported improved blood pressure (improved by approximately 2 mmHg), LDL-C, total cholesterol, and fasting blood glucose, but not other markers of glycemic control or blood lipids or anthropometrics (body weight, BMI, waist circumference), and the quality of evidence was ranked as moderate.[1]
An additional 6 meta-analyses of RCTs have examined cocoa’s effects on blood pressure or endothelial function specifically and reported improvements to blood pressure, arterial stiffness, and blood flow.[7][8][9][10][11] For example, in a 2017 Cochrane review, systolic blood pressure (SBP) and diastolic blood pressure (DBP) were reduced by 1.8 mmHg, and the evidence quality was moderate. When only participants with hypertension were analyzed, there were larger improvements to SBP and DBP (4 mmHg and 2 mmHg, respectively).[12] In other studies, the effects were also found to be greater in adults over age 65, compared to adults over 45,[8] and at higher dosages (more than 36 grams per day).[9]
To put these decreases in blood pressure into context, in the Framingham Heart Study, a decrease of 2 mmHg in diastolic blood pressure corresponded to a 6% reduction in the risk of coronary heart disease. Also, structured exercise of more than 150 min per week has been associated with blood pressure reductions of 3/1.5 mmHg, and the DASH dietary pattern has reduced blood pressure by 5.5/3 mmHg.[8]
There are an additional 2 meta-analyses of RCTs in which the effects of cocoa on blood lipids were examined; they reported improvements to LDL-C and total cholesterol.[13][14] However, in one of the meta-analyses, a subgroup analysis of only high-quality trials showed no effect.[13]
In one meta-analysis of cocoa and body composition[15] and one meta-analysis of cocoa and oxidative stress and inflammation, there were generally no effects, except for a moderate decrease in MDA (high-quality evidence) and a large increase in nitric oxide (low-quality evidence).[16][17]
Additionally, a large body of observational studies has reported associations between dark chocolate consumption and improved cardiovascular disease. In 13 meta-analyses, dark chocolate consumption reduced the risk of cardiovascular diseases, including type 2 diabetes, congestive heart failure, heart attack, and stroke, but not atrial fibrillation. The risks were reduced by 10% to 45% when the participants consumed either a moderate amount or the highest amount of dark chocolate, compared to nonconsumers. The dosage that reduced the risk the most was approximately 2 to 10 grams a day (or 3 servings a week) in some studies.[18][19][20][21][22][23][24][25][26][27][28][29][30][18]