Chocolate, often in the form of confectionart, cookies or cakes, has long been considered harmful to health, due to the presence of notable quantities of sugars and saturated fat from the cocoa butter base inherent to cocoa. However, dark cocoa powder and foods made with Theobroma cacao also contain a diverse array of phenolic phytochemicals with potential healthful qualities.
Various flavonoids like quercetin, luteolin and apigenin have been quantified, along with epicatechin and catechin.1 Additionally, complexes of 2-12 connected catechins, also known as oligomeric procyanidins (OPCs), have been described.2 Also present in cocoa are the methylxanthines theophylline, caffeine and theobromine, the latter two comprising about 99 per cent of the methylxanthine content of cocoa.3 Recent analytical and in vitro antioxidant studies report that a serving of hot cocoa (two tablespoons of non-alkaline processed cocoa—the process of alkalization destroys many of the procyanidins) has about double the phenolic content and antioxidant activity of a serving of green tea or red wine.4
The first evidence suggesting cocoa could operate as an antioxidant in humans appeared in 1996, where a single 35g serving of defatted cocoa given to 12 young men produced an increase in the resistance of LDL cholesterol from being oxidized outside the body.5 A study published four years later administered to 30 young male and female subjects a single serving of one of the following distilled water-based beverages: 18.75g procyanidin-enriched cocoa powder (containing 897mg total epicatechin and oligomeric procyanidins plus 17mg caffeine and 285 mg theobromine) and 12.5g sucrose; 17mg caffeine and 12.5g sucrose (theobromine content was not controlled for); or plain distilled water.6
Those 10 subjects receiving the cocoa beverage displayed significant reductions in blood platelet activation, suggesting a reduced risk to thromboembolic events like stroke or aneurysm.
Additional human studies have sweetened the evidence base for cocoa phenolics and foods containing them. One investigation with 13 male and female middle-aged subjects with systolic hypertension employed a randomised, crossover design with a 100g dark and white chocolate bar. Both bars contained 480kcal and equal amounts of cocoa butter and sugar, with the dark bar also containing 500mg cocoa phenolics, the white bar being devoid of such.7 Subjects consumed one type of bar for 14 days, with blood pressure being measured daily, stopped bar consumption for seven days, and then crossed over to the other colour bar for another 14 days. Only during the dark bar period did both systolic and diastolic blood pressure significantly decline, evidenced by the tenth day of consumption, which reverted back to pre-dark-bar pressures by the second day after cessation.
These observed blood pressure-lowering effects might be ascribed to the ability of cocoa-derived OPCs to inhibit the action of angiotensin I converting enzyme (ACE).8 When ACE is activated, it induces the production of a potent blood vessel constricting/blood pressure-elevating agent called angiotensin II.
Cocoa powder-containing food consumption with a meal has also been shown to boost insulin release after the meal, which may counteract the apparent cardioprotective effects of cocoa-containing products, independent of their effect on blood glucose elevations.9 This effect, if sustained with chronic cocoa product ingestion, could have untoward effects among those with insulin-regulated disorders such as metabolic syndrome, hypertension and diabetes. On the other hand, the recent in vitro finding that cocoa-derived phenolics block the activation of a cellular messenger, one that mediates, in part, insulin resistance in humans, portrays a potentially favourable effect.10,11
The question remains whether chronic ingestion of cocoa phenolic-rich foods can influence markers of cardiovascular function and integrity, in both health and disease states. Dark chocolate could someday emerge as truly being a gift both from—and for—the heart.
1. S?nchez-Rabaneda F, et al. Liquid chromatographic/electrospray ionization tandem mass spectrometric study of the phenolic composition of cocoa (Theobroma cacao). J Mass Spectrom 2003;38:35-42.
2. Porter LJ, et al. Cacao procyanidins - major flavonoids and identification of some minor metabolites. Phytochemistry 1991;30:1657-63.
3. Matissek R. Evaluation of xanthine derivatives in chocolate: nutritional and chemical aspects. Z Lebensm Unters Forsch A 1997;205:175-84.
4. Lee KW, et al. Cocoa has more phenolic phytochemicals and a higher antioxidant capacity than teas and red wine. J Agric Food Chem 2003;51:7292-5.
5. Kondo, K. Inhibition of LDL oxidation by cocoa. Lancet 1996;348:1514.
6. Rein D, et al. Cocoa inhibits platelet activation and function. Am J Clin Nutr 2000;72:30-5.
7. Taubert D, et al. Chocolate and blood pressure in elderly individuals with isolated systolic hypertension. JAMA 2003;290:1029-30.
8. Actis-Goretta L, et al. Inhibition of angiotensin converting enzyme (ACE) activity by flavan-3-ols and procyanidins. FEBS Lett 2003;555:597-600.
9. Brand-Miller J, et al. Cocoa powder increases postprandial insulinemia in lean young adults. J Nutr 2003;133:3149-52.
10. Mackenzie GG, et al. Epicatechin, catechin, and dimeric procyanidins inhibit PMA-induced NF-kappa B activation at multiple steps in Jurkat T cells. FASEB J DOI: 10.1096/fj.03-0402fje. Published online November 20, 2003.
11. Tripathy D, et al. Elevation of free fatty acids induces inflammation and impairs vascular reactivity in healthy subjects. Diabetes 2003;2882-7