An impressive amount of new research on chocolate has appeared in medical journals in the last year. Below is the synopsis of what has been published in the period between May 2012 and August 2013 (note: the highlighted numbers below link to abstracts in PubMed).
First, just a few preliminary facts on cocoa chemistry: Cocoa, or cacao, and, hence, chocolate are some of the highest known sources of the flavanoid (flavan-3-ol) epicatechin, the major flavanoid in chocolate. The activity of cacao and chocolate is considered to be primarily due to and its condensed versions (i.e. procyanidins), as well as theobromine (the main alkaloid in cacao), and magnesium. Other interesting substances recently found in cocoa and chocolate include methylpyrazines, largely responsible for the aroma of chocolate (22972787); N-phenylpropenoyl-l-amino acids, which determine the astringent taste of cocoa (22953909); hydroxycinnamic acids (22931195); and certain amino acids and peptides, some of which possess hypoglycemic activity (23107706, 23862567). Additional health benefits may be obtained by the introduction of fiber from cocoa shells into dietary products (22735710). Other benefits may be provided by the fatty acids in chocolate. And chocolate, typically, has a significant amount of sugars and fat – although moderate consumption of chocolate has not been linked to increased weight and, in fact, seems to promote insulin sensitivity and cardiovascular health.
Therapeutic efficacy and bioactivity of cocoa and chocolate
Some of the most frequently observed benefits of chocolate occur in the cardiovascular system. Compounds in cocoa have a normalizing effect on the endothelial cells nitric oxide (NO) production, normalizing vasodilation and thus preventing high blood pressure (22985936, 22865466, 22982348, 23142352). A Cochrane meta-analysis of 20 studies on human consumption of cocoa products rich in polyphenols determined that two weeks of moderate chocolate consumption typically results in reduction of the systolic and diastolic blood pressure (22895979). Another meta-analysis showed that chocolate consumption appears to reduce the risk of stroke (22933736). Chocolate and its compounds have also been shown to improve platelet function (23136121) and cholesterol levels in both healthy individuals (23823716) and those with high cholesterol (23678635, 23823716). Interestingly, the Kuna people, who consume great amounts of cocoa drinks, are nearly free of cardiovascular diseases and hypertension (PMC3652297).
Chocolate is considered beneficial for metabolic disorder (23704807). It has been estimated that people with high blood pressure and metabolic syndrome (who are considered to be at high risk for cardiovascular disease) will benefit from the preventive benefits of chocolate at the cost of US$42/year (22653982).
In moderately hypercholesterolemic people, a fiber-rich chocolate product decreased plasma glucose, systolic and diastolic blood pressure, and markers of oxidative stress (22689050).
In overweight/obese individuals, polyphenol-rich dark chocolate decreased blood pressure and prevented the rise in fasting insulin, insulin resistance, and increased cortisol levels (22796902). In the same type of subjects, cocoa administered in the form of beverage lowered markers of inflammation and oxidative stress (22854880).
In people with type 2 diabetes, dark chocolate induced protection of the endothelial cell function after 75 g of oral glucose (23039340). Similar results have been obtained in healthy adults (22851734), and chocolate also prevented the rise of blood pressure after the dose of glucose (22851734).
Epicatechin is largely responsible for promoting vasorelaxation via NO-dependent mechanisms (23847022), while theobromine is associated with cholesterol-improving effects of cocoa (23595874). However, theobromine is also known for its diuretic effects: In the early 20th century it has been recommended as a treatment for edema. Epicatechin has been shown to stimulate cardiac angiogenesis, with the effects being almost doubled by combination with exercise (22833114).
Intriguing results have been obtained on the effects of chocolate on the brain and cognitive function. In elderly subjects with mild cognitive impairment, intake of flavanol-rich chocolate for 8 weeks improved several parameters of mental function, which was partially related to the improvement in insulin sensitivity (22892813). Flavanols contained in cocoa were also found to protect neurons (better than resveratrol or other catechins) from damage by mitochondrial toxins and HIV proteins, via modulation of brain-derived neurotrophic factor and related proteins (22886603). In rodents, flavanols have been shown to prevent cognitive decline due to normal aging, stroke, and dementia (23810791) and to reduce the negative effects of amyloid β (23554028). In nematodes, a peptide from cocoa beans prevented the formation of human-type amyloid β plaques, while in snails, epicatechin significantly enhanced memory formation (23014569). However, theobromine, which has often been touted as the potential stimulant compound in chocolate (because of its great similarity to caffeine and having binding affinity to the same receptors), has not been shown to possess caffeine’s effects on mood and vigilance (23764688). At high doses (500-1000 mg), theobromine actually had negative mood effects in healthy human individuals (23420115).
The mechanisms of chocolate’s and cocoa’s actions also involve stimulation of mitochondrial function by epicatechin (23625721, 23791569), modulation of carnitine metabolism (23637065), and tyrosine sulfation. Evidence also includes reports of cocoa reducing postprandial increase of portal vein blood pressure in cirrhosis patients (22811444), preventing onset of type 1 diabetes (23578364) and stimulating insulin secretion (23563558) in mice, suppressing pain-generating molecules in the spinal cord (23576361), reducing oxidative stress associated with chronic arthritis (22728690), suppressing inflammation (23104506, 23576361, 23637048), protecting and restoring the function of skeletal muscles in diabetics (23642227, 23870648), increasing oxygenation in renal tissue (23557792), suppressing adipogenesis (fat formation) and obesity in mice (22641065), and reducing oxidative stress in the heart. It should be noted that chocolate consumption by pregnant women increases the fetal heart rate and activity (23480746), especially if it is a girl (23662674). In some individuals, chocolate may cause migraine (22644176). Cocoa was shown to affect methylation levels in human DNA (23840361), thus altering the expression of human genes. And finally, multiple effects of chocolate on the immune system have been described.
Cocoa production is linked to some issues with biodiversity in cocoa-producing regions (23656506).
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