My favorite time of the morning is when I am sitting outside listening to the house finches sing their hearts out while I sip a cup of strong coffee and nibble on a piece of dark chocolate. Pura vida! What could be better? If it feels this good, it must also be good for you, right? That thought made me wonder, is there really anything to the claims that dark chocolate has beneficial effects on health?


What’s the evidence that dark chocolate is good for you?

My favorite part of breakfast
My favorite part of breakfast

Epidemiological studies have shown that people who regularly indulge in moderate amounts of dark chocolate are less likely to develop high blood pressure or heart disease or suffer strokes. The problem with epidemiological studies is that they can only demonstrate associations between things and cannot prove that one thing causes the other to happen.

There is however, a scientific observation that lends support to these epidemiological studies: dark chocolate has been shown to improve endothelial cell (the cells lining blood vessels) function among healthy volunteers, elderly individuals, postmenopausal women, hypertensive patients, and overweight patients (BMI 25-35 kg body weight). Since hypertension, heart disease and strokes are all diseases that involve blood vessels, this finding suggests dark chocolate could play a causal role in reducing those diseases.


But wait, there is more

A substance in cocoa beans, epicatechin (pronounced epi-Ka-TE-kin), has been shown to improve athletic performance—at least in mice. A paper in the Journal of Physiology in 2011 reported that mice who drank a solution of epicatechin twice a day for fifteen days increased their endurance on a treadmill test compared to control mice who only drank water. In fact, they covered about 50% more distance than the control animals! In addition, the researchers found that the muscles of all of the animals that had been given epicatechin contained new capillaries, as well as biochemical markers indicating that their ceels were making new mitochondria, the tiny organelles that generate energy. These anatomical changes are exactly what is needed for improved performance, more blood supply and greater oxygen capacity.

So what is this wonder molecule, epicatechin? It belongs to a class of molecules called flavanols that have antioxidant activity. But before you reach for your favorite antioxidant supplement, consider this. If the changes were due to antioxidation, wouldn’t you expect that any antioxidant should work? But it appears the effect was specific to epicatechin and not to other antioxidants. The authors of the mouse endurance study concluded that muscle cells likely contain specific receptors that bind epicatechin. When that happens, they say, it “induces an integrated response that includes structural and metabolic changes in skeletal and cardiac muscles resulting in greater endurance capacity.”


What about the brain?

Hippocampal anatomyA small study (37 subjects) in Nature Neuroscience showed that healthy people, ages 50 to 69, who drank a mixture high in cocoa flavanols (epicatechin being the most important) for three months performed better on a memory test than people who drank a low-flavanol mixture. Using a highly sensitive variant of functional magnetic resonance imaging (fMRI), they looked at a specific area of the brain, the dentate gyrus (DG) of the hippocampus. The hippocampus is a sea horse-shaped area in the brain where memories are made and stored. It had been known that decline in the DG function is associated with the decline in age-related memory. But how do you show a definitive cause and effect? One way is to show that DG-associated memory decline in otherwise healthy elders can be improved by interventions that enhance DG function.

Using a high-resolution variant of fMRI, the researchers mapped the precise site of age-related DG dysfunction. They also developed a cognitive task—a pattern recognition test involving the kind of skill used in remembering where you parked the car or recalling the face of someone you just met—whose function is localized to this anatomical site. Then, in a controlled randomized trial, they applied these tools (fMRI and the cognitive task test) to study the subjects who consumed either a high or low cocoa flavanol-containing diet. The high-flavanol group performed about 25 percent better than the low-flavanol group. This result is even more impressive when you learn that the high-flavanol drinkers performed like people two to three decades younger on the study’s memory task!

How can such a remarkable result be explained? Flavanols, and epicatechin, in particular, have been shown to increase blood flow. But this effect is not specific to the hippocampus; other areas of the brain also show increased blood flow. A more likely explanation, according to the authors of the study, is that epicatechin causes an increase in the number of dendrites, the tiny spines that form the connections between neurons. And, such interconnecting groups of neurons are where memories are stored.

The study is obviously small and needs repeating in a larger experiment. But the possibility that age-related memory loss can be reversed with a simple molecule like epicatechin is tantalizing. And that dark chocolate contains this blessed molecule is, well, delicious.


Does it have to be dark?

We keep referring to dark chocolate providing health benefits. What about milk chocolate, the favorite of most people in the U.S? Sorry guys, it turns out that epicatechin is destroyed by the processing involved in the manufacture of milk chocolate. If you want chocolate that is good and good for you, it has to be dark!

Featured photo credit:

Dov Michaeli, MD, PhD
Dov Michaeli, MD, PhD loves to write about the brain and human behavior as well as translate complicated basic science concepts into entertainment for the rest of us. He was a professor at the University of California San Francisco before leaving to enter the world of biotech. He served as the Chief Medical Officer of biotech companies, including Aphton Corporation. He also founded and served as the CEO of Madah Medica, an early stage biotech company developing products to improve post-surgical pain control. He is now retired and enjoys working out, following the stock market, travelling the world, and, of course, writing for TDWI.



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