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Epidemiological studies indicate that populations consuming higher levels of fruits and vegetables are healthier and have lower risk for various diseases, such as cardiovascular disease, cancer and mental disorders. Most likely the health benefits of fruits and vegetables are attributed to their high levels of flavonoids, such as flavanols. Plant rich is flavanols include red wine, black and green tea, many fruits and especially cocoa. In plants flavanols are present as the monomers epicatechin and catechin or oligomers, called procyanidins. Flavanol rich foods have cardio-protective effects. The mechanism by which flavanols act as cardio-protective agents is not well defined. The aim of this review is to discuss the bioavailability, antioxidant properties and bioactivity of flavanols in improving of cardiovascular health.
As opposed to other flavonoids, which naturally consist as glycosides, flavanols are present in food as aglycones, or as polymers or bound to gallic acid. Studies have shown that flavanols and procyanidins are stable during gastric transit. After absorption the flavanols are mainly methylated and glucuronidated or are bound to sulphate. Cacao may have different levels of flavonoids, depending on variety, climate and time of harvest. After harvesting, the cacao beans are subject to fermentation and roasting, which also changes the composition of flavonoids. Depending on the process, as much as 90 percent of flavonoids can be lost. Milk proteins also reduced the antioxidant activity of cacao.
In vitro studies have confirmed the strong antioxidant activity of cocoa flavanols and procyanidins. Flavanols act as antioxidant by donating hydrogen (from the hydroxyl group), thereby neutralizing free radicals, and by chelating metal ions. Cacao has even stronger antioxidant properties than other flavanol rich foods such as red wine, blueberries, garlic and tea. In vivo studies have also confirmed the antioxidant properties of cacao flavanols. Long term feeding studies have shown that cacao increases the antioxidant capacity of the plasma and reduces the oxidation of low density lipoproteins.
Flavanols also have an influence on inflammation, platelet aggregation and endothelial changes caused by nitric oxide. Diseases such as hypertension, hypercholesterolemia, atherosclerosis and heart failure activate pro-inflammatory enzyme systems, which produce free radicals, resulting in reduced nitric oxide levels and oxidation of low density lipoproteins. Flavanols have been shown to stimulate nitric oxide production and to reduce the activities of inflammatory enzymes after intake of ethanol. NF-B transcription factors regulate the expression of genes involved in inflammation and cell proliferation. Studies have shown that epicatechin, catechin and some procyanidins dimers regulate these NF-B transcription factors.
Platelets play an important role in the formation of infarction and stroke. Studies have shown that cacao can help to prevent the aggregation of platelets. Flavanols neutralizes superoxide anions, which are released by platelets and enhance platelet aggregation.
The study concluded that there are many studies that confirm that flavanols and procyanidins from cacao act as antioxidants in vivo. These phytochemicals have an influence on cardiovascular health and platelet aggregation.
Source: CL Keen, RR Holt, PI Oteiza, CG Fraga and HH Schmitz . Dietary Polyphenols and Health: Proceedings of the 1ste International Conference on Polyphenols and Health. American Journal of Clinical Nutrition, Vol. 81, No. 1, 298S-303S, January 2005
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