Chocolate: Cardiovascular Superstar?

Photo Credit: Lisa Morgan

As if we needed more reasons to indulge, a number of recent studies are confirming what our hearts have always known: chocolate can be very good for you!

Based on his studies of the island-dwelling Kuna - who drink up to 40 cups per week of flavanol-rich cocoa and have a 10% lower risk of stroke, heart failure, cancer and diabetes than people who live on mainland Panama - Dr. Norman Hollenberg of Harvard Medical School and Brigham and Women's Hospital, believes epicatechin, a flavanol found in cocoa (and tea and wine), is so protective, it should be classified as a vitamin.

Hollenburg's research, published in the March 2007 issue of the International Journal of Medical Sciences, revealed that compared to the cocoa-loving Kuna islanders, among those living on the Panama mainland, relative risk of death from heart disease was 1,280% higher and death from cancer was 630% higher.

The link between cocoa flavanols and cardiovascular health is likely due in part to their improving blood flow by increasing production of nitric oxide, a molecule secreted by the lining of our blood vessels (the endothelium) to signal surrounding muscle to relax.

In research published in the Journal of Cardiovascular Pharmacology, ((Heiss C, Finis D, et al., February 2007), eleven healthy male smokers, with smoking-related losses in endothelial function resulting in impaired blood flow, drank three cups each day of a flavanol-rich cocoa drink (306 mg flavanol/cup). Within two days, the men showed measurable improvement in blood vessel function. After seven days, impairment of blood flow in these smokers was almost reversed. However, the improvement disappeared within one week of discontinuing the cocoa treatment, prompting researchers to recommend daily consumption of flavanol-rich cocoa.

Cocoa also appears to protect LDL cholesterol from oxidation (only after LDL has been oxidized or damaged by free radicals does it promote atherosclerosis) and increase levels of cardioprotective HDL cholesterol.

Japanese researchers divided 25 subjects with normal and mildly elevated cholesterol into two groups, one of which was given a drink containing 12g of sugar each day while the other group received a mixture of 26g cocoa powder and 12g of sugar each day for 12 weeks. (The cocoa drink contained 377 mg epicatechin, 135 mg catechin, 158 mg procyanidin B2, and 96.1 mg procyanidin C1 per 100g.) Blood samples were collected at the start and end of the trial, and levels of HDL and LDL, as well as LDL's ability to resist oxidation were measured. Compounds in the urine that indicate oxidative stress (free radical damage) were also measured.

After 12 weeks, changes in LDL's susceptibility to oxidation, expressed as lag time (the amount of time after exposure to free radicals before LDL is damaged), were noted. In the sugar only group, LDL became more susceptible to oxidation - a 19.8% reduction in lag time was recorded compared to baseline. In the cocoa group, LDL was protected by a 9.4% prolongation in lag time.

In addition, levels of protective HDL cholesterol increased 23.4% in the cocoa group compared to a 5.1% increase in the sugar-only group.

Cocoa drinkers also experienced an eight-fold increase in catechin excretion, a ten-fold increase in epicatechin excretion, and a significant 24% reduction in the urinary oxidative stress marker, dityrosine. Those drinking cocoa did not experience weight gain or increases in blood pressure or heart rate, and no adverse events were reported.

Confirming blood-pressure lowering effects seen in the Zutphen Elderly Study (Buijsse B, Feskens EJ, et al., Archives of Internal Medicine, 2006) in which older men with the highest cocoa intake had an average 3.7 mm Hg lower systolic and 2.1 mm Hg lower diastolic blood pressure compared to men drinking the least cocoa, a meta-analysis of 5 studies, also published in the Archives of Internal Medicine (Taubert D, Roesen R, et al., April 2007), indicates that cocoa lowers blood pressure as much as beta-blockers or ACE-inhibitors.

Researchers from the University Hospital of Cologne pooled data from 5 randomized controlled trials involving a total of 173 participants on the blood pressure-lowering effects of cocoa, and another 5 involving 343 subjects and looking at green and black tea.

In the cocoa studies, 87 were assigned to consume cocoa, and 86 served as controls. One third (34%) of the participants had high blood pressure. After an average follow-up of two weeks, both systolic and diastolic blood pressure dropped in the cocoa-consuming groups. Compared to controls, the cocoa drinkers experienced an average decrease of 4.7 mm Hg in systolic blood pressure and a drop of 2.8 mm Hg in diastolic blood pressure.

Hypertension is defined as having a systolic and diastolic BP greater than 140 and 90 mm Hg. "At the population level, a reduction of 4 to 5 mm Hg in systolic blood pressure [the top number, when the heart contracts] and 2 to 3 mm Hg in diastolic blood pressure [the bottom number, when the heart relaxes] would be expected to substantially reduce the risk of stroke (by about 20%), coronary heart disease (by 10%), and all-cause mortality (by 8%)," said the study's authors.

No such benefits were reported for the 343 individuals in the 5 tea studies (171 drinking tea, and 172 controls), an outcome researchers think is due to the difference in the polyphenols found tea and cocoa. While both are rich in polyphenols, black and green tea contain more flavan-3-ols, while cocoa contains more procyanids.

Practical Tips: Enjoy catechin-rich cocoa to your heart's content. Polyphenol-rich foods, including cocoa, green tea and red wine, are good for you. Remember, however, that unlike that consumed by the Kuna islanders, cocoa in our culture is typically delivered with lots of cardio-compromising sugar and fat. For a sophisticated cocoa true to your heart, try mixing unsweetened organic cocoa powder with low-fat milk, a dash of vanilla or cinnamon, and a spoonful of honey.

One other tip: The more bitter your cocoa, the more likely it is to contain a healthy serving of flavanols. Flavanols, including catechins, are sometimes removed from commercial cocoas because they tend to have a somewhat bitter taste.

Lara Pizzorno

Bayard V, Chamorro F, Motta J, Hollenberg NK. Does flavanol intake influence mortality from nitric oxide-dependent processes? Ischemic heart disease, stroke, diabetes mellitus, and cancer in Panama. Int J Med Sci. 2007 Mar;4:53-58. PMID: 17299579

Heiss C, Finis D, Kleinbongard R, Hoffmann A, Rassaf T, Kelm M, Sies H. Sustained increase in flow-mediated dilation after daily intake of high-flavanol cocoa drink over 1 week. J Cardio Pharm. 2007 Feb;49(2):74-80. PMID: 17299579

Baba S, Osakabe N, Kato Y, Natsume M, Yasuda A, Kido T, Fukuda K, Muto Y, Kondo K. Continuous intake of polyphenolic compounds containing cocoa powder reduces LDL oxidative susceptibility and has beneficial effects on plasma HDL-cholesterol concentrations in humans. Am J Clin Nutr. 2007 Mar;85(3):709-17. PMID: 17344491

Taubert D, Roesen R, Schomig E. Effect of cocoa and tea intake on blood pressure: a meta-analysis. Arch Intern Med. 2007 Apr 9;167(7):626-34. PMID: 17420419

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