What Is the Evidence That Cocoa Flavanols Improve Health?

An ongoing argument often surfaces around certain holidays, especially 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? Many readers would like to know.

Do Cocoa Flavanols Improve Health, or Is That Claim Hooey?

Q. I’ve been hearing that cocoa flavanols are good for you. Can you tell me more about the benefits and any risks?

A. The flavanols found in cocoa have several beneficial activities in humans. Among other effects, they help keep blood platelets from clumping together to form clots (Frontiers in Pharmacology, March 12, 2024).  This should reduce cardiovascular risk.

In addition, cocoa flavanols help protect blood vessels from constriction related to stress (Food & Function, Nov. 25, 2024).  There is also evidence that cocoa flavanols, along with compounds from red berries, can modulate gut microbiota in a positive direction (Nutrients, May 13, 2023).

The main drawback is in finding a source that provides cocoa flavanols without excess calories. A review by ConsumerLab.com shows that flavanol levels vary widely both in dark chocolate and supplements. CocoaVia Brain Health Memory+ is among the site’s top picks. It provides a robust and reliable source of cocoa flavanols without sugar or fat and with minimal heavy metal contamination. We also appreciate CocoaVia’s support of our People’s Pharmacy newsletter and podcast.

How Cocoa Flavanols Improve Health After a High-Fat Meal and Stress:

Results from a really important study, the COSMOS trial, seem pretty definitive about the health benefits of cocoa flavanols for long-term intake. (Read on for more details about that one.) That study used cocoa flavanols supplied by Mars that are very similar to the CocoaVia capsules we just mentioned.

Moreover, a different study shows that even young, healthy people could benefit in the short-term from cocoa flavanols if they make some dubious food choices.The latest research comes from a British study published in the journal Food & Function (Nov. 18, 2024). This randomized, counterbalanced, double-blinded, crossover, postprandial intervention study examined the impact of a high-flavanol beverage on vascular function.

The young healthy volunteers had to consume a high-fat meal consisting of two butter croissants with 10 grams of salted butter, one and a half slices of cheddar cheese and 8 and ½ ounces of whole milk containing either  high-flavanol or low-flavanol cocoa powder. After an hour and a half, the subjects completed an 8-minute mental stress test. It involved a mathematical task that kept increasing in speed accompanied by a loud aversive buzzer after an incorrect response and after every 10 answers.

The stress test produced increases in heart rate and blood pressure. The fatty foods reduced blood vessel function that lasted for at least an hour and a half after the meal. But the high-flavanol cocoa beverage actually mitigated the decline in vascular function. The researchers had anticipated that cocoa flavanols improve health in part by increasing oxygenation in the brain. They did not confirm this effect.

The authors conclude, however, that

“flavonoid-rich foods have the potential to acutely protect endothelial function against poor food choices, such as high-fat snacks, during episodes of stress in young healthy adults.”

For the purposes of the study, the researchers utilized a special high-flavanol cocoa (Natural Acticoa) from the Swiss chocolate manufacturer Barry Callebaut. This product is designed for companies that make chocolate products. As a result, it might be hard to find, but cocoa flavanols are not. We recommend CocoaVia as the most accessible and reliable concentrated source of cocoa flavanols. Disclosure: CocoaVia sponsors our radio shows and podcasts. That doesn’t change our assessment that it is a great low-calorie source for flavanols.

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.