Cocoa and the Brain

Cocoa….the word conjures up the beloved treat, chocolate, of which cocoa beans are the main ingredients.  Sadly, most chocolates are not healthy.  This is largely due to their added ingredients such as sugar, fat and milk ingredients.  But the healthfulness of chocolate also depends on the amount of unprocessed cocoa in the chocolate product.  Researchers are now discovering that the health benefits that come from cocoa are substantial.  New research is increasing our understanding of why this is so.

Over the past couple of decades, evidence has been accumulating regarding the health effects of a group of phytochemicals known as flavonoids.  For humans, phytochemicals are obtained by eating the plants which produce these molecules as a form of defense against competitors, pathogens and predators.  Flavonoids are known to provide protection against vascular disease and cardiovascular-related death through the enhancement of blood flow.  But research has unveiled hints that these same benefits in the blood vessels of the brain could help to reverse age-related declines in cognitive performance.  Flavonoids have shown an ability to increase the number of, and strength of, connections between neurons in the brain as well as to reduce the loss of neurons during aging.  In-depth studies are now delving more deeply into the beneficial effects of flavonoids in the brain and the mechanisms behind their actions (1).

A new study, recently published in November 2020, is shedding a brighter light on this subject.  It examined a sub-family of flavonoids known as flavanols.  Flavanols are found in high concentrations in foods such as grapes, berries, apples, red wine, cocoa and green tea.  Research had already revealed that flavanol ingestion could improve the function of arteries quite rapidly, even after a single dose, by boosting their capacity to dilate.  Some studies showed improvements in blood pressure and blood flow comparable to those of drugs.  Cocoa flavanols specifically were identified as agents that could enhance the function of blood vessels, resulting in more oxygen being delivered all around the body. (2)

Why is this important?  Every cell, tissue and organ in the human body is dependent upon oxygen, not only to function efficiently but to stay alive.  When we breathe, oxygen is taken in as a component of the air that we breathe.  It enters the lungs and makes its way into the tiny alveoli, microscopic air sacs within the lungs which are intimately linked to the smallest blood vessels of the body, known as capillaries.  Here, rapid exchange of oxygen gas can take place between the lungs and the bloodstream.   The absorbed oxygen is then carried throughout the body by the blood to be used for such important body processes as nutrient breakdown and energy production (3).

The source of the beneficial effect of flavanols on blood vessels is a gas called nitric oxide.  This gas is produced by endothelial cells, the specialized cells that line the inside walls of blood vessels.  The small size of nitric oxide molecules allows them to move rapidly through cell membranes to reach their target cells, the smooth muscles of the blood vessel walls, where they exert their positive effect on the flow of blood through these vessels.  Cocoa flavanols (mainly epicatechins and catechins) can exert their influence on multiple steps of the reactions that take place, both during the production of nitric oxide in blood vessels, and as nitric oxide exerts its dilation effect on the blood vessels.  Flavanols can modulate receptors, activate and suppress various enzymes, neutralize free radicals and control the rate and extent of oxidation reactions.  In this way, cocoa flavanols encourage optimum nitric oxide levels in blood vessels, supporting the delivery of enough oxygen to all areas and processes in the body (4).

The healthful activities of flavanols have been known for a while but little study had been performed on their impacts in the brain.  Ongoing research was suggesting that cocoa flavanols might provide benefits to cognition.  Elderly people display lower oxygen levels in the brain as do people with dementia.  Perhaps if more oxygen could be delivered to brain cells, the cognitive decline commonly seen with aging might be lessened.  Protection against neuropsychiatric disorders might also be realized.  Could the actions of flavanols be benefitting more than just the cardiovascular system? (2).


The Study (2)

This small randomized double-blind study examined 18 young, non-smoking men between the ages of 18 and 40 who had no known brain, heart, vascular or respiratory disorders.  Women were excluded to reduce any interference that might arise from hormonal fluctuations during the menstrual cycle.  Participants were asked to refrain from vigorous exercise, alcohol consumption and eating foods rich in flavonoids and other polyphenols (fruits, vegetables, cocoa, chocolate, coffee, tea, fruit juices and wine) as well as high-nitrate foods (beetroot, spinach, lettuce, rocket/arugula, celery, parsley and cabbage) for 24 hours before the study began.  They were also asked to fast for 12 hours before each study visit.

The frontal cortex of the brain is a key area involved in decision making.  Before each study intervention, the oxygenation of the frontal cortex of the brain of each participant was measured using near-infrared spectroscopy to get a baseline measurement.  Then, in two separate trials, investigators looked at what happened in the brain after the participants consumed a cocoa drink.  In the first trial, the subjects drank flavanol-rich cocoa and in the second they consumed low-flavanol cocoa.  This was a double-blind trial in which neither the participants nor the researchers knew which cocoa drink the subjects were receiving.

The drink used in the study was a mixture of unprocessed cocoa powder in water containing either a high level of cocoa flavanols (150 mg of epicatechin and 35.5 mg of catechin) or a low level of cocoa flavanols (4 mg each of epicatechin and catechin).  Both mixtures were identical in texture, consistency and taste.

Two hours after consuming the cocoa drink, the brains of the participants were challenged by a standard procedure in which participants breathed in air containing 5% carbon dioxide, a level about 100 times the concentration as that of normal air.  The usual response to this by the brain is to increase its blood flow to bring in more oxygen and eliminate the carbon dioxide.  During each trial, the oxygenation of the frontal cortex of the brain in each participant was again measured.  Next, the participants were challenged with a number of progressively complex cognitive tests.  An example of one test used is the Stroop task, a standard test of cognitive processing.  It consists of colour names written out in colours not corresponding to the one being presented.  The test-taker has to state the colour in which the word is written and ignore what the actual word is.

Fourteen out of the eighteen subjects in this study reacted to the high-flavanol drink with an approximately three times higher maximum frontal cortex oxygenation which was achieved more quickly compared with the effect of the low-flavanol drink.  The same participants solved complex cognitive tests 11% faster on average after drinking the high-flavanol mixture.  There was no measurable difference in the time needed to solve easier puzzles.

The four subjects that did not respond to the cocoa drink with either increased oxygenation or improvement on cognitive tests already had very high brain oxygenation levels at baseline.  It appears that their blood flow was already optimized, apparently leaving little room for further enhancement.

Researchers attributed the better brain oxygenation to increased dilation of the blood vessels through the production of nitric oxide in the blood vessels.  This is the first time that a relationship has been shown between the cerebrovascular effects and the cognitive effects of flavanols.  It was also noteworthy that such a significant effect appeared after a single dose of flavanols.


What we can learn from this research

Though this study was small, it provides new information on the power of flavanols.  It offers good news for people at higher risk of cognitive impairment, for instance, those with certain types of genes or a family history that suggests higher risk; those suffering from chronic conditions such as cardiovascular disease or diabetes; and smokers.  Though further research utilizing larger groups of participants is needed, this research reinforces the results of previous investigations regarding the value of flavanols for better blood flow and, in addition, it presents the potential added benefit of better cognitive function in later life (2).


Now, back to cocoa and chocolate…

Raw cocoa beans are bitter and virtually inedible with most of the bitterness coming from their flavanol content.  Traditional chocolate-making involves considerable processing of cocoa beans – grinding, fermentation, alkalization, roasting, and separation of the material into cocoa powder and cocoa butter.  The process of alkalization (also known as “dutching” to make “dutch” cocoa) is one that is often used to mellow the flavour of the chocolate.  However, this process strips away most of the flavanols.

Happily, commercial chocolate manufacturers are now starting to realize that discerning consumers are looking for healthier treats.  Some chocolate-makers have begun shifting their goals to include higher flavanols is some products, so it may be possible even now to buy truly healthy chocolate.  There are a few problems with this though (5,6);

  • Most manufacturers do not label the flavanol content of their chocolate and it may take quite a search to find one that does.
  • Even when flavanol amounts are stated, the levels offered may not be high enough to realize any health benefits. The optimal daily flavanol intake for health is still unclear.  The EFSA (European Food Safety Authority) has recommended consuming at least 200 mg of cocoa flavanols daily, which they state can be found in 2.5 grams of high-flavanol cocoa powder or 10 grams of high-flavanol dark chocolate.  More recently, however, this amount has been contested.   Many sources now believe that the actual healthy daily amount of cocoa flavanols might be as high as 900 mg.  This requires a very large amount of chocolate, between 100 and 500 gm daily, an amount that is not practical to eat every day.  The extra calories would be very high as would amounts of other added unhealthy ingredients such as sugar and fat.  Obviously, further clinical studies are necessary to identify the correct required daily dose.
  • Keep in mind that high-flavanol chocolate might take a bit of getting used to. Remember, flavanols are bitter.  It is amazing though how our taste palettes can change with enough motivation.

No worries though.  Here are some suggestions for acquiring the flavanols you need in order to gain the cardiovascular and cognitive benefits they offer (7,2,4);

  • Forget about using chocolate as your only source of flavanols.
  • There are a variety of alternative flavanol-rich foods including black grapes, apples, berries, cherries, pears, peaches, green tea, and pulses. Eating enough of many different sources of flavanol-rich foods every day can provide the levels that you are looking for.
  • Continue to enjoy chocolate in moderation when you want to. Buy chocolate labelled to be high in cocoa solids.  Unless the package states flavanol content, you will have no idea how much flavanol it contains.  That would depend on the type of cocoa used by the manufacturer and how it was processed.  But this doesn’t matter if you are eating other flavanol-rich foods.
  • It is now possible to find cocoa powders that contain as much as 10% by weight of flavanols. Even if you can’t find this type of product, non-alkalized cocoa powder is very available and still retains much of its original flavanol content.  Use it to make up some hot chocolate, adding a small amount of sugar, or a batch of Black Bean Brownies, sweetened with dates.  (Look under ”Recipes” on this website for our favourite Black Bean Brownie recipe.)  Or create a chocolate smoothie, adding in frozen bananas and plant-based milk.  These steps can give you another little extra boost of flavanol.



1  Spencer, J.P.E., Vauzour, D., Rendeiro, C.  Flavonoids and cognition: the molecular mechanisms underlying their behavioural effects.  Arch Biochem Biophys. 2009 Dec; 492(1-2):1-9. Doi:10.1016/

2  Gratton, G., Weaver, S.R., Burley, C.V., Low, K.A., Maclin, E.L., Johns, P.W., Pham, Q.S., Lucas, S.J.E., Fabiani, M., Rendeiro, C.  Dietary flavanols improve cerebral cortical oxygenation and cognition in healthy adults. Sci Rep 10, 19409 (2020).

3  Meletis, C., Wilkesa, K.  The Crucial Role of Oxygen for Health.  Journal of Restorative Medicine. Feb 15,2019; 8(1).

4  Fraga, C.,Litterio, C., Prince, P., Calabró,  V., Piotrkowski, B., Galleano, M.  Cocoa flavanols: Effects on vascular nitric oxide and blood pressure. Journal of clinical biochemistry and nutrition. 2011; 48. 63-7. 10.3164/jcbn.11-010FR.

5  Ludovici, F., Barthelmes, J., Nägele, M.P., Enseleit, F., Ferri, C., Flammer, A.J., Ruschitzka, F., Sudanol, I.  Cocoa, Blood Pressure, and Vascular Function.  Front Nutr. 2017; 4: 36.  Doi: 10.3389/fnut.2017.00036.

6  Vlachojannis, J., Erne, P., Zimmermann, B., Chrubasik-Hausmann, S.  The Impact of Cocoa Flavanols on Cardiovascular Health.  Phytother Res. 2016 Oct; 30(10): 1641-1657. Doi: 10.1002/ptr.5665.

7  Vlachojannis, J., Zimmermann, P.E.B., Chrubasik‐Hausmann, S.   The Impact of Cocoa Flavanols on Cardiovascular Health.  , Phytotherapy Research. October 2016; 30(10): 1641-1657.





Promoting a healthy adventurous lifestyle powered by plants and the strength of scientific evidence.

My name is Debra Harley (BScPhm) and I welcome you to my retirement project, this website. Over the course of a life many lessons are learned, altering deeply-rooted ideas and creating new passions.


  1. Ruth Russell on September 25, 2021 at 2:40 pm

    Great article Deb. I always learn something new when I read your articles… Many thanks for your dedication to researching food and how it affects our bodies.

    • Deb on October 4, 2021 at 9:15 pm

      Thanks so much, Ruth!

    • Deb on October 24, 2021 at 7:06 am

      Thanks, Ruth. The topic of the relationship between food and health is a fascinating one to me.

  2. Susan Rees on September 25, 2021 at 5:27 am

    Keep up the great work you’re doing. Thanks for sharing your wealth of knowledge.

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