Dark Chocolate and Your Arteries

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Dark Chocolate. Lew Robertson/Digital Vision/Getty Images

For over a decade evidence has been accumulating that eating dark chocolate can have a beneficial effect on cardiovascular health. These benefits may include a reduction in heart attacks and stroke.

A study published in 2011 in the British Medical Journal attempted to summarize the effect of chocolate on heart health. Investigators performed a meta analysis of seven prior studies that had enrolled over 100,000 participants.

They found that participants who consumed the highest amounts of chocolate had a 29% reduction in strokes, and a 37% reduction in cardiovascular disease, compared to participants who consumed very low amounts of chocolate. In this analysis, it was not clear whether dark chocolate offered more benefit than milk chocolate.

In the intervening years, however, it has become clearer that dark chocolate is more beneficial to cardiovascular health than milk chocolate. This is thought to be because dark chocolate contains far more flavenols than milk chocolate. Flavenols relax arteries, thus reducing blood pressure and stress on the arteries, by producing nitric oxide in the arterial walls.

The Latest on Dark Chocolate

In March of 2014, in the Federation of American Societies for Experimental Biology Journal, investigators from The Netherlands studied both the acute and chronic effects of consuming dark chocolate on arterial health.

Shortly after eating 70 grams (about 2.5 ounces) of dark chocolate, research subjects had significantly reduced blood pressures.

Research subjects then ate 70 grams of dark chocolate each day for four weeks. Subsequent measurements showed, as expected, the same relaxation in the arterial walls and the reduced blood pressures that were seen after acute ingestion of chocolate.

In addition, the chronic ingestion of dark chocolate produced a significant reduction in markers of inflammation, suggesting that the process of atherosclerosis was being inhibited. (Atherosclerosis leads to the plaques that cause coronary artery disease (CAD), strokes, and peripheral artery disease (PAD)).

The good news is that these beneficial changes occurred with regular dark chocolate to the same extent as they occurred with “flavanol-enriched” types of dark chocolate. This is good news because the flavenol-enriched dark chocolate products cost a lot more - and (most people think) they don’t taste nearly as good as the regular dark chocolate.

Dark Chocolate and Claudication

Claudication is the medical name for the leg pain or leg cramps experienced during exercise by many patients with PAD. In July, 2014, investigators from Rome reported in the Journal of the American Heart Association that eating dark chocolate improves claudication in patients who suffer from this symptom. Specifically, after eating dark chocolate, these patients were able to walk significantly farther without symptoms than they were before consuming the chocolate.

 This reduction in claudication was seen only after eating dark chocolate - there was no benefit in these patients after eating milk chocolate.

The Bottom Line

Evidence continues to build that eating chocolate (in particular, dark chocolate) tends to improve vascular health. The beneficial effects are most likely explained by the flavanols present in dark chocolate (which are also present in milk chocolate, but to a much lesser extent). It appears that regular dark chocolate has all the flavanols necessary to achieve a maximum effect, and that eating flavanol-enhanced dark chocolate (or, for that matter, "extra doses" of regular dark chocolate) is not necessary to get all the benefits.

Eating dark chocolate has both immediate effects (relaxing arteries, reducing blood pressure, improving the ability to walk without claudication in people with PAD), and chronic effects (reducing markers of inflammation, and potentially slowing atherosclerosis.)

However, because dark chocolate is loaded with calories (about 500 calories for every 100 grams - or about 3.5 oz - of dark chocolate), the panels of experts who produce clinical guidelines are exceedingly reluctant to recommend that we all begin consuming dark chocolate. They’re afraid we’ll all get fat, thus contributing to the obesity epidemic, and entirely wiping out any of the benefits we might gain from the chocolate itself.

The experts have a point. If you are considering adding dark chocolate to your efforts to prevent cardiovascular disease, keep in mind the inherent trade-off between the benefits of dark chocolate and the detriment of added calories, and limit yourself to no more than a couple of ounces of dark chocolate a day.

References:

Buitrago-Lopez A., Sanderson J, , Johnson L, et al. Chocolate consumption and cardiometabolic disorders: systematic review and meta-analysis. BMJ, 2011; 343 (aug26 1): d4488 DOI: 10.1136/bmj.d4488

Esser D, Mars M, Oosterink E, et al. Dark chocolate consumption improves leukocyte adhesion factors and vascular function in overweight men. FASEB J 2014; 28:1464–1473. Abstract

Loffredo L, Perri L, Catasca E, et al. Dark chocolate acutely improves walking autonomy in patients with peripheral artery disease. J Am Heart Assoc 2014; DOI:10.1161/JAHA.114.001072. Available at: http://jaha.ahajournals.org.

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