Above: Cocoa beans and powder (image © istockphoto.com/joannawnuk)

What if you could make your brain work better by eating dark chocolate or drinking hot cocoa? Well, it might be possible, thanks to flavanols! Cocoa beans, which are the main ingredient in chocolate, contain lots of these compounds. And researchers have found that consuming foods rich in flavanols is linked to more efficient blood flow, which can lead to improved brain function.

Did you know? Compounds called flavanols give unprocessed cocoa a very strong smell and taste. When making chocolate, cocoa beans are fermented, alkalized, and roasted to improve the flavour.In one British study, volunteers who drank a cocoa beverage high in flavanols had increased blood flow to their grey matter. Grey matter is on the inside of your brain and the outside of your spinal cord. It controls movement, learning, memory, emotions, and language. After it processes information, grey matter hands the results over to white matter, which is found on the outside of your brain and the inside of your spinal cord. While grey matter processes information, white matter is responsible for transmitting it to different parts of your body. So it’s not surprising that a group of Japanese researchers found that people with more grey matter have better cognitive function. In other words, they think better.

When it is processing information, grey matter needs a constant supply of oxygen. Altogether, your brain uses about 20 per cent of all the oxygen in your blood. But all of the thinking that goes on inside your grey matter means that it needs a bigger share of that oxygen. The brain and spinal cord are made up of about 40 per cent grey matter and sixty per cent white matter. Yet the grey matter consumes 94 per cent of the oxygen in your brain!

In particular, grey matter contains large numbers of neurons (brain cells) with unmyelinated axons. These are thin extensions that transmit information between neurons. But unlike the axons in white matter, unmyelinated axons are not surrounded by myelin. This fatty protein substance provides insulation and helps boosts the strength of the long-distance signals sent from the white matter to various parts of your body. And because myelin has a high percentage of fats (70%) compared to proteins (30%), it requires little to no oxygen. As a result, the unmyelinated axons in your grey matter need more blood flow than the myelinated axons in your white matter.

Did you know? Even dark chocolate has relatively low levels of flavanols. But it's still healthier because it's lower in fats and sugars than milk chocolate.As they try to find ways of increasing oxygen supply to the brain, researchers have focused on flavanols. How do flavanols help deliver the oxygen that your grey matter needs? Flavanols contain methylxanthines. These chemicals cause the airways of the lungs to dilate (open up) and constricted (tightened) blood vessels to relax. As a result, blood pumps more efficiently and more oxygen can get to where it’s needed.

Diagram of a neuron, showing the axon extending out of the cell body as well as myelin surrounding the axon (Wikimedia Commons). Click image to enlarge

For example, in a recent study on whether eating chocolate can improve cognitive function, 37 adults were given 900 milligrams of flavanols every day for three months. Researchers found that the participants had increased blood flow to the hippocampus. That's the region of the brain responsible for learning and memory. The hippocampus also contains a lot of the grey matter to perform these essential tasks. Tests have also shown that people who consume more flavanols are better at recognizing visual patterns and taking memory tests.

So does this mean you can go ahead and treat yourself as much chocolate as you want? Sorry, but not even the authors of these studies go that far! That’s because most flavanols are lost during the chocolate-making process. To to achieve the effect seen in the last study (900 miligrams of flavanols), you would have to consume ten bars of dark chocolate daily! Milk chocolate has even less flavanols (about 14 milligrams per bar), since most of the cocoa is replaced by milk and sugar. Small amounts of flavanols are found in vegetables, legumes, tea, red wine. Fruits such as oranges, berries, pomegranates, and apples also contain traces of the compounds.

Did you know? Cocoa butter is a fat found in chocolate that contains oleic acid, a “good” type of monounsaturated fat also found in olive oil.Nonetheless, these studies suggest that consuming large quantities of cocoa flavanols might help prevent memory loss and improve brain function in older people. This is a particularly exciting possibility as countries around the world face the challenge of caring for ageing populations. In particular, researchers hope to use medications containing flavanols to treat neurodegenerative diseases like Parkinson’s and Alzheimer’s.

Even without the benefits of flavanols, chocolate would still be a rich and delicious treat to enjoy on any occasion. So don’t forget to add it to your list of yummy study snacks. It might just give your brain the boost it needs to stay energized through those long study sessions!

Learn more!

News articles on the health benefits (and problems) associated with chocolate, including as a source of flavanols:

Cocoa antioxidant sweetens cognition in elderly (2014)
Bethany Brookshire, ScienceNews

Heart Health Benefits of Chocolate (2012)
Cleveland Clinic

The Problem with Chocolate (2007)
Tara Parker-Pope, New York Times

Scientific articles on the health benefits of flavanols:

Cerebral blood flow response to flavanol-rich cocoa in healthy elderly humans (2008)
F. A. Sorond, L. A. Lipsitz, N. K. Hollenberg & N. D. FIsher, Neuropsychiatric disease and treatment 4

Does flavanol intake influence mortality from nitric oxide-dependent processes? Ischemic heart disease, stroke, diabetes mellitus, and cancer in Panama (2007)
V. Bayard, F. Chamorro, J. Motta & N. K. Hollenberg, International Journal of Medical Sciences 4

Scientific articles on research related to grey matter and white matter:

Spatial navigational strategies correlate with gray matter in the hippocampus of healthy older adults tested in a virtual maze (2013)
K. Konishi & V. Bohbot, Frontiers in Aging Neuroscience

Correlation between gray/white matter volume and cognition in healthy elderly people (2011)
Y. Taki et al., Brain and cognition 75
Link to abstract. Registration or subscription required to view full text.

Variation with age in the volumes of grey and white matter in the cerebral hemispheres of man: measurements with an image analyser (1980)
A. K. H. Miller, R. L. Alston & J. A. N. Corsellis, Neuropathology and Applied Neurobiology 6
Link to abstract. Registration or subscription required to view full text.

Ninh Khuong

Ninh is completing her third year of undergrad in Biochemistry at Mount Allison University, NB. She was a Let's Talk Science volunteer for two years before she became an outreach coordinator. She also writes for The Argosy, 7Mondays, and The CHMA. Aside from writing and volunteering for Let's Talk Science, she enjoys swimming, running, writing poetry, painting, cooking, traveling, and playing the piano.

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