Flashback Friday: Dark Chocolate and Artery Function

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.

Chocolate: beauty, or the beast, or both? Although cocoa itself is frequently found in foods like “chocolate which can contain high levels of fat and sugar,” the cocoa powder itself “may have beneficial effects in a number of chronic disease conditions, including [heart] disease.”

Flow-mediated dilation, measured in the main artery of the arm, which is about the same caliber as our coronary arteries, is considered one of the best measures of arterial function—a predictor of cardiovascular mortality. A little bit of cocoa doesn’t do anything. But a little more, or a lot more, gives one a significant boost in arterial function within hours of consumption. How much does it take? Not much—just a teaspoon of natural cocoa powder, which would be like a tablespoon or more of Dutch cocoa.

Now, makes you a little suspicious that the author works in Hershey, Pennsylvania, at the Hershey Medical Center, and, indeed, has accepted money from our largest chocolate manufacturer’s Center for Health and Nutrition, conveniently located near the intersection of Chocolate and Cocoa Avenues.

Putting together all of the best available science, though—dozens of randomized controlled trials—arterial function was significantly improved within hours, and after weeks and months of chronic cocoa consumption. It’s always difficult to tease out fact from fiction when such powerful financial interests are involved. “Many [of these] studies were funded by industry” as well, “and [as] in all areas of research evidence suggests that industry funding is associated with pro-industry conclusions.” But, even after removing “those studies funded by industry,” they found the same protective effect.

The reason they measure arterial function in the arm, rather than where you really need it—the coronary arteries of the heart—is that that would require an angiogram, which is a little more invasive. But if you were able to find people already scheduled for an angiogram anyway… Here we go.

Double-blind randomized trial finds that dark chocolate actually opens up coronary arteries themselves. And, when they did what’s called a cold-pressor test, where they plunge your hand into a bucket of ice water—which normally causes your arteries to constrict—but, after dark chocolate, they dilated. Dark chocolate may also improve blood flow to the heart of our kidneys.

“Because chocolate also contains fat and sugar,” though, we have to be careful. “Furthermore, most chocolate products are manufactured with milk, a compound known to influence antioxidant…capacity in [our blood].” Even if milk chocolate had the same flavonoid phytonutrient content as dark chocolate, “the antioxidant effect of cocoa is potentially [weakened] in the [blood]” when milk is consumed.

So, not only are there triple the antioxidants in dark, compared to milk, chocolate, but the milk actively works against the effects in the human body. So, eat dark chocolate, and get a nice spike in the antioxidant power of our bloodstream within an hour. Milk chocolate—nothing. And, if you eat that same dark chocolate with a cup of milk, the benefit is suppressed. The “[a]ddition of milk”—either in our stomach, or in the chocolate itself—”inhibits the [within-body] antioxidant activity of chocolate and the absorption into the bloodstream of [one of the target phytonutrients].”

Sugar isn’t good for us, either. Sugar impairs arterial function. One bottle of soda’s worth of sugar can temporarily cripple arterial function. That’s why sugar-free cocoa improves arterial function better than the same amount of cocoa with sugar added. So, “[e]liminating sugar…appears to amplify the beneficial effects of cocoa.”

Bottom line: “Although the positive effects of chocolate and cocoa products seem apparent, precautions exist” when we’re talking about the calories, fat, and sugar in chocolate. Cocoa powder, then, offers the best of both worlds. “Although [not as tasty], cocoa-based products with little or no sugar or…fat are certainly preferred.” And, you can make them tasty, as I note in my healthy chocolate milkshake recipe, and my healthy chocolate ice cream video.

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Images thanks to Bob.Fornal via flickr and Bronayur via Wikimedia