A recent article (1) discusses how cocoa contributes to heart health. This article is an interesting review. It discusses the history, as well as the proposed biological actions of cocoa. The biological actions it focuses on are the actions of the flavonoids present in cocoa.
Because of the belief that cocoa acts to induce nitric oxide, the writer first discusses the history of nitroglycerin. She includes its use by Alfred Nobel as an explosive. An interesting twist she relates is Alfred Nobel's need to take nitroglycerin as a medication later in life for his angina.
Then the author discusses how the processing of cocoa affects the flavonoids during the drying, fermentation and roasting phases of processing. However, a discussion of the use of alkali to produce Dutched cocoa is missing. Alkali processing gives Dutched cocoa an even greater potassium content, as discussed here.
There is a discussion of two populations studied for their cocoa intake. The author discusses the Kuna of Panama because of their migration into an urban life. The other group she discusses is a group of Dutch.
Both studies show a lower blood pressure among cocoa consumers. In the case of the Kuna, those who consumed over 5 cups of cocoa daily had lower blood pressure. In comparison, their urban counterparts did not consume cocoa. Similarly in the Dutch study, the cocoa consumers getting 4 gm/da lowered their blood pressure. And the lowest group of cocoa consumers took in no cocoa.
Flavonoids In Cocoa
Without considering other substances present in cocoa, the emphasis then turns to the flavonoids in cocoa. The flavonoids in cocoa are plentiful. Because flavonoids are present in other foods associated with good heart health, flavonoids are the subject of much research today.
Generally, there are four main properties that determine the mechanism of action of flavonoids. Specifically, the four properties are anti-oxidant properties, anti-inflammatory properties, reduction of platelet aggregation, and vascular relaxation.
Many studies report the anti-oxidant activity of flavonoids. However, these studies were test tube studies instead of cellular studies. Because the test tube measurements of anti-oxidant level lack correlation with cellular anti-oxidant activity, these studies are no longer relevant to how the cell fights free radicals.
Subsequently, investigators today are developing valid cellular anti-oxidant studies. For example, TBARS assay is emerging as one of the promising cellular anti-oxidant tests. It measures the peroxidation of lipids in the cell. Several studies show that cocoa liquor polyphenols reduce TBARS. But until researchers develop the cellular tests more, the value of these tests will be difficult to know.
Also, the effects of flavonoids on inflammation are in the early stages of study. Testing of flavonol fractions are determining how they affect cytokine responses. Likewise, LDL oxidation is in the early stage of study. Some studies show LDL, oxidized LDL and apo B to be reduced by flavonols from cocoa.
Likewise, platelet adhesion studies are in their early stages. Previously, in laboratory tests, cocoa reduced platelet adhesion. In a subsequent study, humans consumed cocoa for 4 weeks. Consequently, this reduced the activation of a platelet glycoprotein involved in aggregation. Specifically, cocoa lowered P-selectin in the subjects' platelets. And this reduced aggregation of their platelets.
Several studies show increased vasodilatation from flavonoids. Investigators believe the vasodilatation to be related to an increase in nitric oxide synthase. The result is an increase in nitric oxide (NO). Nitric oxide is an intermediary that activates potassium channels in vascular endothelium and smooth muscle. Activation of these channels results in vascular relaxation.
The mechanism of vasodilatation for flavonoids appears similar to the effect of polyunsaturated fats (PUFAs), discussed here. PUFAs also activate potassium channels. In the case of PUFAs, multiple publications detail the mechanisms of their action at the molecular level. Flavonoids do not have as many details as PUFAs. But a clearer picture is beginning to emerge.
As with PUFAs, flavonoids partially make up for a poorer potassium sodium ratio by allowing activation of potassium channels at a lower level of potassium in the cell. Flavonoids are an excellent adjunct to an adequate potassium sodium ratio. And they may have additional healthy effects yet to be discovered. Cocoa, along with a number of other foods, is a great source of flavonoids and potassium. If the cocoa is Dutched, it is an even better source of potassium.
1. Cocoa and heart health: a historical review of the science. Pucciarelli DL. Nutrients. 2013 Sep 26;5(10):3854-70. doi: 10.3390/nu5103854.