Cocoa Flavanols Simply Explained

1. What It Is About

Cocoa flavanols belong to the flavonoids, a large group of plant substances. Such substances are formed by plants themselves; they are not vitamins. In the cocoa bean they occur in different forms: small building blocks such as epicatechin and catechin and larger chains made from them, which are called procyanidins. Raw cocoa contains the most of them. During roasting, alkalising and the production of chocolate a large part is lost. Therefore dark chocolate and pure cocoa extracts differ in how much of these substances they actually contain.

For understanding the studies it is important: cocoa flavanols are not a single substance but a mixture. The small building blocks reach the blood quickly. The larger chains are hardly absorbed and end up in the colon, where they are processed by the gut bacteria. There they can trigger other processes than the small forms. In studies, therefore, it is usually measured how much of the small building blocks arrives in the blood or how well an artery can dilate.

2. What Studies Show

The blood vessels are the best studied. In a study with 16 people with coronary artery disease the participants drank a beverage with high cocoa flavanols or a comparison beverage with otherwise identical composition for 30 days. With the flavanol-rich beverage the artery in the upper arm could dilate significantly better, which shows that the vessel wall functions better 5. The group was small, and whether this results in fewer heart attacks was not examined.

A study with 22 healthy people compared a beverage with high and one with low cocoa flavanols over four weeks. With high cocoa flavanols bacteria species considered beneficial increased in the stool while others decreased. At the same time an inflammation marker in the blood and blood lipid levels decreased. How closely the increase in beneficial bacteria and the decrease in the inflammation marker are connected could only be partly explained 1.

Cognitive performance was examined in older people. 90 older participants drank a beverage with high, medium or low cocoa flavanols for eight weeks. In the two groups with more cocoa flavanols tasks in which numbers and letters had to be connected in a certain order were solved faster, and word fluency was better. A short general memory test, however, showed no differences 3.

In another study with 60 older people over 30 days cerebral blood flow responded better during a task, and the participants became faster in a test with letters and numbers 6.

Regarding blood pressure and glucose metabolism 19 people with high blood pressure and impaired glucose metabolism received dark chocolate with many plant substances or white chocolate without for 15 days. In the group with the dark chocolate blood pressure decreased and several measures of insulin action improved. The chocolate, however, also contained other plant substances, so the effect cannot be attributed to the cocoa flavanols alone 2.

3. What Remains Unclear

Most studies last only weeks to months. Almost always an intermediate value is measured, for example how well an artery dilates, and not whether people become ill less often. The large COSMOS study 4 tested cocoa extract and a multivitamin separately. For the primary endpoint it found no clear reduction in cardiovascular events for the cocoa extract. This finding applies to the tested cocoa extract and not to cocoa flavanols alone. The lower number of cardiovascular deaths was an additional finding there.

Complicating factors include the differences between the studies: some tested dark chocolate, others pure extracts. The amounts used varied widely. Chocolate can hardly be blinded due to taste and texture. In addition chocolate always brought further substances, so it remains open which share of the observations is attributable to the cocoa flavanols. How differently individual people respond to the same amount is also still open.

4. What This Means in Everyday Life

Anyone wishing to classify the study situation can separate two things: the short-term measured changes in blood vessels, inflammation markers and metabolic values, for which there are several indicative studies, and the question whether this results in fewer heart attacks, strokes or dementia cases. For the second point the answer is still outstanding.

The amounts used in the studies were in some cases clearly above what is achievable through normal nutrition. Dark chocolate usually contains less of them than the extracts studied. Chocolate also brings sugar and fat, which were not the focus in the studies.

The next points to clarify are whether the observed short-term changes persist with longer intake, whether they also occur in people with existing diseases and which substance in the cocoa mixture plays which role.

All details with study numbers and sources: Detailed Page on Cocoa Flavanols. For children: Cocoa Flavanols for Children.