A recent article (1) discusses how cocoa contributes to heart health. This article is an interesting review, discussing 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 it is believed 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 his need to take nitroglycerin as a medication later in life for his angina.
The author then discusses how the processing of cocoa affects the flavonoids during the drying, fermentation and roasting phases of processing. What is missing is the discussion of the use of alkali to produce Dutched cocoa, which gives Dutched cocoa an even greater potassium content, as discussed here.
There is a discussion of two populations studied for their cocoa intake. The Kuna of Panama have been studied because of their migration into an urban life. The other group studied was a group of Dutch.
Both studies show a lower blood pressure among cocoa consumers. In the case of the Kuna, those who did not migrate consumed over 5 cups of cocoa daily compared to their urban counterparts who did not consume cocoa. In the case of the Dutch study, the cocoa consumers got 4 gm/da and the lowest group 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. The four general properties being studied to determine the mechanism of action of flavonoids are: the anti-oxidant properties, the anti-inflammatory properties, the reduction of platelet aggregation, and vascular relaxation.
Many of the studies on anti-oxidant activity of flavonoids were done in the test tube instead of in the cell. Because the test tube measurements of anti-oxidant level have been shown to lack correlation with cellular anti-oxidant activity, these studies are no longer relevant.
The emphasis today is on developing valid cellular anti-oxidant studies. TBARS is emerging as one of the promising cellular anti-oxidant tests. It measures the peroxidation of lipids in the cell. Cocoa liquor polyphenols have been observed to reduce TBARS. But until the cellular tests are developed more, the value of these tests will be difficult to know.
Effects of flavonoids on inflammation are also in the early stages of study. Flavonol fractions are being tested to determine how they affect cytokine responses. LDL oxidation is also in the early stage of study. LDL, oxidized LDL and apo B were shown to be reduced by flavonols from cocoa.
Cocoa in laboratory tests was found to reduce platelet adhesion by reducing the activation of a platelet glycoprotein involved in aggregation. When human subjects were fed cocoa for 4 weeks, the cocoa lowered P-selectin in their platelets and reduced aggregation of their platelets.
Several studies have shown increased vasodilatation from flavonoids. The vasodilatation is believed to be related to an increase in nitric oxide synthase. The result is an increase in nitric oxide (NO), which is an intermediary that activates potassium channels in vascular endothelium and smooth muscle. Activation of these channels is well known to lead to 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 the details of their action are known at the molecular level. More details are needed for flavonoids, 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 may have additional healthy effects. 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.