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What Is the Evidence That Cocoa Flavanols Improve Health?

The COSMOS trial and other studies lead to the conclusion that cocoa flavanols improve health.

An ongoing argument often surfaces around Valentine’s Day, Easter and Halloween. You’ll see a number of feature pieces suggesting that chocolate is actually good for you. These stories are frequently counterbalanced by others pointing out that chocolate is high in sugar and fat, and therefore also pretty high in calories. Consequently, they say, chocolate is not good for you at all. In truth, though the question is really about the plant compounds in chocolate. Is there real evidence that cocoa flavanols improve health? There is quite a bit of research on this topic, but results from a really important study seem pretty definitive.

COSMOS Trial Reveals How Much Cocoa Flavanols Improve Health:

Nutrition nerds have been waiting for the results of a large dietary supplement trial called COSMOS. (That stands for COcoa Supplement and Multivitamin Outcomes Study.) Now the researchers who conducted the trial have analyzed the main data and published their conclusions. The results are very encouraging (American Journal of Clinical Nutrition, March 16, 2022).

This study was a really big randomized double-blind placebo-controlled trial. That is the gold standard for research. This experiment involved 21,442 Americans over more than three years. The investigators are among the most respected nutrition researchers in the world, affiliated with Harvard University.

I (Terry) participated as a subject in this study. We volunteers knew that we had a 50/50 chance of taking a standard multivitamin or a placebo, and likewise a 50/50 chance of taking a high-dose (500 mg) cocoa flavanol supplement or placebo. The researchers wanted to know whether cocoa flavanols would help protect people from cardiovascular complications. They also wondered whether people taking vitamins would have a lower likelihood of being diagnosed with cancer.

The Cardiovascular Benefits of Cocoa Flavanols:

For the trial, 10,719 participants took cocoa flavanol capsules, while 10,723 took look-alike placebo pills. During about three and a half years, 410 of those on actual cocoa extract experienced angina, a heart attack, stroke, revascularization, artery surgery or death from one of these problems. There were 456 such events among those taking placebo pills. That’s a 10 percent difference. It’s not nothing, but it’s not much to write home about. It is not statistically significant.

That conglomeration of events was the main, or primary, outcome that the researchers reviewed. However, they also took a look at a “secondary” outcome, death from cardiovascular causes. This is where things get interesting. People taking the cocoa extract supplements were 27 percent less likely to die from heart disease, stroke or other cardiovascular catastrophes during the study.

Even more impressive, when the scientists calculated risk just for people who actually took the pills every day as intended, cocoa flavanols reduced death from cardiovascular causes by a solid 39 percent. That seems important to us. We don’t know of any medications that healthy people would take to reduce their risk of dying from cardiovascular problems by that much.

Multivitamins Did Not Reduce the Risk of Cancer:

The investigators also designed COSMOS to reveal if multivitamins could help protect participants from cancer. This part was perhaps a disappointment for multivitamin fans (American Journal of Clinical Nutrition, March 16, 2022). There was no real difference between the multivitamin takers and those on placebo. Those taking multivitamins did have a 38 percent reduced risk of lung cancer, however. Moreover, the researchers did not note any safety concerns for either supplement.

This summary of the COSMOS results so far comes from the AAAS EurekAlert press release and the online publications in the American Journal of Clinical Nutrition. In addition, I (Terry) referred to an email summary that the COSMOS investigators provided the study volunteers. What you have just read is independent of CocoaVia marketing.

A few years ago, a doctor scolded us for accepting “advertising” (in public radio, we call it “underwriting”) from a supplement maker. Here is that exchange.

Do Cocoa Flavanols Improve Health or Harm It?

Q. As a physician, I’m concerned about the ethics of advertising supplements. Some of these products are touted to support brain and heart health. There is no evidence behind such claims. You’ve said cocoa flavanols improve health, and you should be ashamed of yourselves.

A. There are certainly products being advertised that are not supported by clinical trials. We definitely share your concerns about them. We disagree about cocoa flavanols, however.

When it comes to CocoaVia, the underwriter on our syndicated radio show, there is a substantial body of research. Cocoa flavanols can lower blood pressure modestly (Cochrane Database of Systematic Reviews, April 25, 2017).  They may do this by making blood vessels more flexible (Journal of Agricultural and Food Chemistry, online Aug. 12, 2019).  In addition, cocoa flavanols can reduce markers of inflammation (Frontiers in Immunology, April 24, 2019).

Mars Edge provided the cocoa flavanol extract (and the placebo) for the COSMOS study mentioned above and below. (The company did not design the study or participate in data collection or analysis.) Although these capsules were made specifically for the study, the cocoa extract and the dose is essentially similar to that provided by CocoaVia Cardio Health products.

Cocoa Flavanols and the Brain:

As for cognitive function, researchers have done fewer studies.

However, a systematic review of 12 studies found

a positive effect of cocoa polyphenols on memory and executive function” (Plant Foods for Human Nutrition, Jan. 13, 2020).

In addition, Harvard researchers are currently conducting a large placebo-controlled study to see whether cocoa flavanols improve health. The COcoa Supplement and Multivitamin Outcomes Study (COSMOS) has enrolled more than 18,000 older individuals who will take either cocoa flavanols or placebo plus multivitamin or placebo for four years. Beyond cardiovascular outcomes and cancer, the researchers are also collecting information on cognitive function, macular degeneration and cataracts. As the study is still underway, we shall have to wait several years for the scientists to finish collecting and analyzing all the data before we will know what it can tell us about cocoa flavanols and the aging brain.

Obviously, that was all we knew back then. But now we know that cocoa flavanols can, in fact, reduce our risk of dying from cardiovascular causes. That’s a pretty strong indication that cocoa flavanols improve health. We still need to wait for further analysis to learn their results on whether cocoa flavanols also protect memory and brain power. Other studies have already demonstrated benefits for specific cognitive functions.

Where Can You Find Cocoa Flavanols?

We’ve already mentioned the calories in chocolate candy. The compounds themselves do not provide many calories, but candy certainly can. Moreover, not all chocolate candy is rich in cocoa flavanols. When we are looking for a good source of these compounds, we start with CocoaVia. Yes, they do underwrite our radio show. But they also provide the highest amount of cocoa flavanols per serving (500 mg) with very low levels of the toxic element cadmium. Much as we love it, chocolate really doesn’t come close.

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About the Author
Terry Graedon, PhD, is a medical anthropologist and co-host of The People’s Pharmacy radio show, co-author of The People’s Pharmacy syndicated newspaper columns and numerous books, and co-founder of The People’s Pharmacy website. Terry taught in the Duke University School of Nursing and was an adjunct assistant professor in the Department of Anthropology. She is a Fellow of the Society of Applied Anthropology. Terry is one of the country's leading authorities on the science behind folk remedies..
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  • Sesso HD et al, "Effect of cocoa flavanol supplementation for prevention of cardiovascular disease events: The COSMOS randomized clinical trial." American Journal of Clinical Nutrition, March 16, 2022. https://doi.org/10.1093/ajcn/nqac055
  • Sesso HD et al, "Multivitamins in the prevention of cancer and cardiovascular disease: The COSMOS randomized clinical trial." American Journal of Clinical Nutrition, March 16, 2022. https://doi.org/10.1093/ajcn/nqac056
  • Ried K et al, "Effect of cocoa on blood pressure." Cochrane Database of Systematic Reviews, April 25, 2017. DOI: 10.1002/14651858.CD008893.pub3
  • Grone M et al, "Cocoa flavanols improve endothelial functional integrity in healthy young and elderly subjects." Journal of Agricultural and Food Chemistry, online Aug. 12, 2019. DOI: 10.1021/acs.jafc.9b02251
  • Ruiz-Léon AM et al, "Clinical advances in immunonutrition and atherosclerosis: A review." Frontiers in Immunology, April 24, 2019. DOI: 10.3389/fimmu.2019.00837
  • Barrera-Reyes PK et al, "Effects of cocoa-derived polyphenols on cognitive function in humans. Systematic review and analysis of methodological aspects." Plant Foods for Human Nutrition, Jan. 13, 2020. DOI: 10.1007/s11130-019-00779-x
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