The Heart Health Benefits of Cocoa vs. Chocolate

Michael Greger M.D. FACLM · October 21, 2026 ·

The massive COSMOS trial with more than 20,000 study participants found that eating the equivalent of one and a half tablespoons of natural cocoa powder a day can significantly reduce cardiovascular mortality risk.

Discuss

Transcript

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

In 2011, a study on the “acute effect of dark chocolate” was published, randomizing smokers to a small bar of dark chocolate or milk chocolate. The milk chocolate failed to offer any significant benefit, but within two hours of having dark chocolate, there was a significant improvement in artery dysfunction. As you can see the smokers started out with only half the artery function of nonsmokers, but after the dark chocolate, nearly achieved the normal artery function of non-smokers.

This gave researchers the idea to test dark chocolate in other populations with artery dysfunction, resulting in the 2014 publication of—spoiler alert—“Dark Chocolate Acutely Improves Walking Autonomy in Patients with Peripheral Artery Disease.”

The study had the same set up. Peripheral artery disease patients ate a bar of dark chocolate or milk chocolate, then, two hours later, were put on a treadmill to see how long they could walk before the pain in their calves became too great. The researchers found that “dark but not milk chocolate acutely improves walking autonomy.” The dark chocolate group was only able to last about 17 more seconds, though, walking about a dozen extra yards. So, the bittersweet truth is that we should not expect chocoholics to be running marathons anytime soon. But that was just after a single bar. What if they kept it up?

There have been 17 randomized, controlled trials putting dark chocolate to the test for improving artery function, and, overall, a meta-analysis found beneficial effects for both acute and chronic dark chocolate consumption.

One of the problems with publishing research on chocolate is that the press jumps on it, oversimplifying and sensationalizing the message, and then the money starts rolling in from candy companies and the message gets muddied even more. As a result, an important idea is lost in all the frenzy: The flavanol phytonutrients in cocoa appear to be beneficial, improving blood flow throughout our body, but the sugar, fat, and excess calories in chocolate aren’t good for us. However, natural-cocoa–powder can be considered a health food.

So, adding cocoa to a smoothie or oatmeal, for example, would be health-promoting. Try to use unprocessed, un-Dutched cocoa. The beneficial flavanols are what give cocoa its bitterness, so manufacturers try to process cocoa with alkali to destroy them on purpose. When it comes to cocoa, bitter is better.

Natural cocoa was pitted against highly alkalinized cocoa in a study of older individuals. Compared to darker Dutched cocoa, lighter natural cocoa not only led to significant improvements in measures of oxidate stress and other lab tests on their blood, but also significant benefits for physical performance, frailty indicators, and quality of life. The natural cocoa group beat out the alkalized cocoa group in every single one of five tests of upper and lower body strength and function. It was time to test out cocoa for peripheral artery disease, and here we go with another spoiler.

The COCOA-PAD study randomized men and women suffering from peripheral artery disease to either three tablespoons of cocoa powder or placebo every day for six months in a double-blind trial. The primary outcome was walking performance assessed by measuring their six-minute walk distance. Participants are asked to cover as much distance as possible walking up and down a hundred-foot hallway for six minutes. Even just 12 meters is considered a meaningful change by that metric, and 34 meters a large meaningful change. The cocoa group beat out the placebo group by about 43 meters.

The cocoa did more than just improve blood flow. Researchers took biopsies from the calf muscles of participants and found improved mitochondrial activity in the muscles of the cocoa group compared to the placebo group. Mitochondria are the little power plants in our cells. This is consistent with a study in which biopsies from the quads of people before and after three months of dark chocolate and cocoa revealed improved mitochondrial structure.

The apparent increases in mitochondrial function, after eating just half a bar of dark chocolate a day for three months, were assumed to be the mechanism by which sedentary subjects around fifty years old improved their exercise capacity. “Overall,” the accompanying editorial to the COCOA-PAD study concluded, “the muscle biopsy findings bolster the concept that cocoa may have persistent protective effects in patients with peripheral artery disease.”

Cardiologist commentators concluded that pilot studies like COCOA-PAD are insufficient to “advocate widespread prescription of cocoa to peripheral artery disease patients.” Though they concede the “neglectable risk, low costs and potential benefit,” they demand “further proof.” That makes sense if we’re talking about some new drug, but what’s the downside of making your life a little more chocolatey by adding some cocoa powder to our daily diet? They stress the “‘therapeutic pleasure” of cocoa consumption must not replace established standards such as walking training, smoking cessation and vigorous optimization of cardiovascular risk.” I agree, but who said anything about replacing? We can do all of the above. That’s the wonderful thing about dietary approaches to disease.

If cocoa flavanols are so artery-friendly, might they be able to save lives? In my book How Not To Hurt, in the section Preventing death-by-chocolate, I explore the COSMOS, trial, that remarkably randomized more than 20,000 people to a cocoa extract or placebo to see what cocoa flavanols can do. Though it was funded by candy bar giant Mars, the study found that years of cocoa supplementation did not reduce the risk of bone fractures, or have any effect on cognitive function, or reduce the risk of diabetes, or high blood pressure, or macular degeneration. What it could do, though, is apparently reduce the risk of cardiovascular death by 27 percent. And it may be even greater than that if adherence is taken into account.

If we only consider those who claimed compliance with taking the pills (or, even better, those with elevated cocoa flavanol levels in their urine, which helps prove they were actually taking them), cardiovascular mortality—and, indeed, overall risk of dying from any cause—appeared to be cut by as much as half. Now, by segmenting the study participants this way, you lose the benefit of randomization (since those who are more compliant with taking pills may also happen to be the type of people who eat more healthfully or exercise more), but those are quite extraordinary numbers and helped convince me to cocoa my groats. (I add some with defrosted frozen cherries for a morning-time chocolate-covered cherry sensation.) The extract dose used in the study corresponds to eating as little as one and a half tablespoons of natural cocoa powder a day.

Please consider volunteering to help out on the site.

Sources

Acknowledgements

Motion graphics by Avo Media

Topics

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

In 2011, a study on the “acute effect of dark chocolate” was published, randomizing smokers to a small bar of dark chocolate or milk chocolate. The milk chocolate failed to offer any significant benefit, but within two hours of having dark chocolate, there was a significant improvement in artery dysfunction. As you can see the smokers started out with only half the artery function of nonsmokers, but after the dark chocolate, nearly achieved the normal artery function of non-smokers.

This gave researchers the idea to test dark chocolate in other populations with artery dysfunction, resulting in the 2014 publication of—spoiler alert—“Dark Chocolate Acutely Improves Walking Autonomy in Patients with Peripheral Artery Disease.”

The study had the same set up. Peripheral artery disease patients ate a bar of dark chocolate or milk chocolate, then, two hours later, were put on a treadmill to see how long they could walk before the pain in their calves became too great. The researchers found that “dark but not milk chocolate acutely improves walking autonomy.” The dark chocolate group was only able to last about 17 more seconds, though, walking about a dozen extra yards. So, the bittersweet truth is that we should not expect chocoholics to be running marathons anytime soon. But that was just after a single bar. What if they kept it up?

There have been 17 randomized, controlled trials putting dark chocolate to the test for improving artery function, and, overall, a meta-analysis found beneficial effects for both acute and chronic dark chocolate consumption.

One of the problems with publishing research on chocolate is that the press jumps on it, oversimplifying and sensationalizing the message, and then the money starts rolling in from candy companies and the message gets muddied even more. As a result, an important idea is lost in all the frenzy: The flavanol phytonutrients in cocoa appear to be beneficial, improving blood flow throughout our body, but the sugar, fat, and excess calories in chocolate aren’t good for us. However, natural-cocoa–powder can be considered a health food.

So, adding cocoa to a smoothie or oatmeal, for example, would be health-promoting. Try to use unprocessed, un-Dutched cocoa. The beneficial flavanols are what give cocoa its bitterness, so manufacturers try to process cocoa with alkali to destroy them on purpose. When it comes to cocoa, bitter is better.

Natural cocoa was pitted against highly alkalinized cocoa in a study of older individuals. Compared to darker Dutched cocoa, lighter natural cocoa not only led to significant improvements in measures of oxidate stress and other lab tests on their blood, but also significant benefits for physical performance, frailty indicators, and quality of life. The natural cocoa group beat out the alkalized cocoa group in every single one of five tests of upper and lower body strength and function. It was time to test out cocoa for peripheral artery disease, and here we go with another spoiler.

The COCOA-PAD study randomized men and women suffering from peripheral artery disease to either three tablespoons of cocoa powder or placebo every day for six months in a double-blind trial. The primary outcome was walking performance assessed by measuring their six-minute walk distance. Participants are asked to cover as much distance as possible walking up and down a hundred-foot hallway for six minutes. Even just 12 meters is considered a meaningful change by that metric, and 34 meters a large meaningful change. The cocoa group beat out the placebo group by about 43 meters.

The cocoa did more than just improve blood flow. Researchers took biopsies from the calf muscles of participants and found improved mitochondrial activity in the muscles of the cocoa group compared to the placebo group. Mitochondria are the little power plants in our cells. This is consistent with a study in which biopsies from the quads of people before and after three months of dark chocolate and cocoa revealed improved mitochondrial structure.

The apparent increases in mitochondrial function, after eating just half a bar of dark chocolate a day for three months, were assumed to be the mechanism by which sedentary subjects around fifty years old improved their exercise capacity. “Overall,” the accompanying editorial to the COCOA-PAD study concluded, “the muscle biopsy findings bolster the concept that cocoa may have persistent protective effects in patients with peripheral artery disease.”

Cardiologist commentators concluded that pilot studies like COCOA-PAD are insufficient to “advocate widespread prescription of cocoa to peripheral artery disease patients.” Though they concede the “neglectable risk, low costs and potential benefit,” they demand “further proof.” That makes sense if we’re talking about some new drug, but what’s the downside of making your life a little more chocolatey by adding some cocoa powder to our daily diet? They stress the “‘therapeutic pleasure” of cocoa consumption must not replace established standards such as walking training, smoking cessation and vigorous optimization of cardiovascular risk.” I agree, but who said anything about replacing? We can do all of the above. That’s the wonderful thing about dietary approaches to disease.

If cocoa flavanols are so artery-friendly, might they be able to save lives? In my book How Not To Hurt, in the section Preventing death-by-chocolate, I explore the COSMOS, trial, that remarkably randomized more than 20,000 people to a cocoa extract or placebo to see what cocoa flavanols can do. Though it was funded by candy bar giant Mars, the study found that years of cocoa supplementation did not reduce the risk of bone fractures, or have any effect on cognitive function, or reduce the risk of diabetes, or high blood pressure, or macular degeneration. What it could do, though, is apparently reduce the risk of cardiovascular death by 27 percent. And it may be even greater than that if adherence is taken into account.

If we only consider those who claimed compliance with taking the pills (or, even better, those with elevated cocoa flavanol levels in their urine, which helps prove they were actually taking them), cardiovascular mortality—and, indeed, overall risk of dying from any cause—appeared to be cut by as much as half. Now, by segmenting the study participants this way, you lose the benefit of randomization (since those who are more compliant with taking pills may also happen to be the type of people who eat more healthfully or exercise more), but those are quite extraordinary numbers and helped convince me to cocoa my groats. (I add some with defrosted frozen cherries for a morning-time chocolate-covered cherry sensation.) The extract dose used in the study corresponds to eating as little as one and a half tablespoons of natural cocoa powder a day.

Please consider volunteering to help out on the site.

Motion graphics by Avo Media

Doctor's Note

Want to learn even more about cocoa and chocolate? See:

For one of my favorite breakfast recipes, see Dr. Greger in the Kitchen: Cran-Chocolate Pomegranate BROL Bowl.

Check out my new book How Not to Hurt, available now for preorders. (All proceeds received from the book are donated directly to charity.)

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