Chocolate and cocoa: health effects reviewed
What it found
Cocoa and chocolate contain substances that may help blood pressure, blood sugar, cholesterol and gut bacteria, but the authors say most human evidence is still limited.
Many findings come from lab tests and animal studies, not people.
What they found
Studies in people
Weight and blood fats
A meta-analysis found no overall effect of cocoa or dark chocolate on weight, BMI or waist circumference, but a subgroup analysis showed reduced weight and BMI with 30 g or more per day for 4 to 8 weeks. Another meta-analysis found that dark chocolate or cocoa lowered total and LDL cholesterol in the short term but had no effect on HDL or triglycerides. A study in normal weight obese women eating 100 g of dark chocolate daily for one week found a rise in HDL cholesterol and a drop in the LDL/HDL ratio and abdomen circumference.
Studies in people and animals
Heart and blood vessels
A meta-analysis of randomized trials found that chocolate and cocoa increased flow-mediated vasodilatation and reduced systolic and diastolic blood pressure and serum insulin levels. A Swedish study linked chocolate eaten 3 to 4 times a week or more with lower risk of heart attack and ischemic heart disease, but other large studies found no link with heart failure, atrial fibrillation or coronary heart disease.
Blood sugar control
Cocoa and its flavonols may improve blood sugar control by slowing carbohydrate digestion and absorption in the gut and by improving insulin sensitivity. Some human studies linked higher chocolate intake with lower risk of type 2 diabetes, but a meta-analysis suggested the protective effect peaked at 2 servings a week and disappeared above 6 servings a week. A 4-week trial found that dark chocolate with negligible polyphenols raised fasting insulin and insulin resistance, while polyphenol-rich chocolate did not.
Cancer
Results on cancer are mixed. Early studies suggested excess chocolate intake might be a predisposing factor for colorectal and breast cancer. Lab studies found cocoa inhibited cancer cell growth, and animal studies found cocoa procyanidins reduced lung carcinomas, thyroid adenomas, mammary and pancreatic tumors, and colon aberrant crypt foci in rats and mice.
Gut bacteria
In rats, a cocoa diet for 6 weeks reduced Bacteroides, Clostridium and Staphylococcus and lowered intestinal immunoglobulin A. In pigs, cocoa increased Lactobacillus and Bifidobacterium in the gut. A human study found that 494 mg of cocoa flavonoids a day for 4 weeks significantly affected the growth of gut bacteria.
Brain and mood
In healthy volunteers, eating 100 g of dark chocolate increased glucose uptake in several brain areas. A study in elderly people linked chocolate intake with lower risk of cognitive decline over 48 months, but a longer follow-up found no link. The paper also mentions chocolate addiction affecting 40% of women and 15% of men in Western countries, and that eating carbohydrates can increase brain serotonin, producing energy and pleasure.
What the authors conclude
“In conclusion, further translational studies need to evaluate all possible effects related to consuming chocolate and to verify in humans the effects hitherto demonstrated only in vitro and on animals.”
Also in their conclusions
- They say cocoa and chocolate act as functional foods because both carry substances that contribute to beneficial health effects.
- They stress that several studies evaluated the health-promoting properties of cocoa and not of chocolate itself, and that the role of chocolate on human health cannot be completely compared to that of cocoa because processing reduces polyphenols.
- They conclude that further translational studies are needed to evaluate all possible effects of consuming chocolate and to verify in humans the effects so far shown only in lab tests and animals, and to suggest how best to consume chocolate in the daily diet.
How it was done
Interest in chocolate has grown because of its possible effects on blood pressure, insulin, blood vessels, oxidation, gut bacteria, blood sugar and fat metabolism. The authors wanted to review the main evidence on cocoa and chocolate and their possible effects on human health.
They reviewed published studies on cocoa and chocolate, including lab tests, animal experiments and human studies. These covered heart and blood vessel effects, blood sugar control, cancer, obesity and blood fats, gut bacteria, the immune system, the brain, mood and sexual function.
What it can’t tell you
- Many of the findings come from lab tests and animal studies, which cannot show what happens in people.
- The human studies are mostly observational, so they can show links but not cause and effect.
- The authors note that confounders such as other diet components, lifestyle, exact chocolate consumption and chocolate composition strongly limit the strength of the evidence.
Who paid
- Conflicts
- The authors declare no conflict of interest.
- Authors work at
- University of Bari Aldo Moro, Italy
The paper
- Title
- Chocolate, "Food of the Gods": History, Science, and Human Health
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Cite
- Montagna MT, Diella G, Triggiano F, et al (2019). Chocolate, "Food of the Gods": History, Science, and Human Health. International journal of environmental research and public health. doi:10.3390/ijerph16244960Free full textPubMed 31817669DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error