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• The perks of dark chocolate: it may be health-promoting

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The perks of dark chocolate: it may be health-promoting

If it tastes good it must be bad, so the saying goes, but delicious dark chocolate may be the exception to the rule.

The 18 July 2005 online edition of Hypertension reports that in addition to all the pleasurable sensations associated with chocolate, this sweet may also help lower blood pressure by an average of 10 percent while improving the body's sensitivity to insulin. However, this benefit applies only to dark chocolate, which is rich in flavonoids — the same antioxidant compounds found in fruits, vegetables and whole grains that are known to help lower blood pressure.

Co-author Jeffrey B. Blumberg, professor of nutrition and senior scientist at the Jean Mayer USDA Human Nutrition Research Centre on Ageing at Tufts University Boston, states that “… chocolate is not only a pleasurable food, it also fits in quite nicely with other healthy recommendations. Research found that three ounces (90 grams) of dark chocolate per day over several weeks reduced blood pressure in individuals with essential hypertension, and also seemed to provide a benefit on their insulin sensitivity."

How the study was conducted
In their study, Blumberg's team had 10 men and 10 women eat 3.5 ounces of dark chocolate every day for 15 days. All of these people had high blood pressure and none were taking blood pressure medications.

First, the researchers had five of the men and five of the women eat dark chocolate while the others ate white chocolate, which contains no flavonoids. Then after another week of no chocolate, the groups "crossed over" and ate the other chocolate.

In the 15 days they were eating dark chocolate, individuals displayed an average 11.9 mm Hg drop in their systolic blood pressure (the top number in a blood pressure reading) and a 8.5 mm Hg drop in diastolic blood pressure (the lower number). However, there was no indication of a drop in blood pressure when they ate flavonoid-free white chocolate.

Given these results, Blumberg believes that dark chocolate can be good for you. But he cautions that you can not just eat chocolate on top of your diet. “Chocolate is still a high-calorie food. You don't want to have excess calories or put on weight if you have hypertension. But as part of a healthful diet, it is something that you can enjoy and not feel you are violating the principles of a healthful diet. Further, being able to enjoy some chocolate can make it easier to stay on a healthy diet that is rich in fruits, vegetables and whole grains."

What other researchers say ….
Dr David L. Katz, associate clinical professor of public health and director of the Prevention Research Centre at Yale University School of Medicine, says that while dark chocolate may be health-promoting his own research into the benefits of chocolate noted that chocolate is rich not only in antioxidants, but also magnesium and fibre. “The predominant saturated fat in dark chocolate —stearic acid—does not raise cholesterol or harm blood vessels. Milk chocolate and white chocolate do not offer any known health benefits, and provide more calories, sugar, and potentially harmful oils than dark chocolate.

Dr Jeffrey Mechanick, director of the Metabolic Support Service at Mount Sinai School of Medicine, is hesitant to recommend dark chocolate as a health food. He says that without more definitive data on whether chocolate promotes weight gain that might outweigh its benefits he would never advise individuals with heart or diabetic conditions to eat more dark chocolate.

However, Mechanick is more lenient for people who do not have these health problems suggesting that his preference is still to indicate that dark chocolate may have some benefit because they are still unproven and there could be risks involved. And, it is not an alternative to traditional lifestyle changes or taking medications to reduce risk of heart disease or treat diabetes.

Dr Charalambos Vlachopoulos and his colleagues at the Athens Medical School in Greece, report in the American Journal of Hypertension that “Epidemiological studies suggest that high flavonoid intake confers a benefit on cardiovascular outcome ”.

Researchers in this study tested the effects of flavonoid-rich dark chocolate on blood-vessel function in 17 young, healthy volunteers over a 3-hour period after they had consumed 100 grams of a commercially available dark chocolate. Observation revealed that an artery in the arm dilated significantly more in response to an increase in blood flow, indicating that elasticity and stiffness of arteries are important determinants of cardiovascular performance and predictors of cardiovascular risk.

Vlachopoulos and his colleagues, report that “chocolate consumption also led to a significant 7-percent decrease in aortic stiffness. The predominant mechanism appears to be dilation of small and medium-sized peripheral arteries and arterioles. His research team did not detect any change in antioxidant levels, so there may be other possible explanations. The dilatory effect of chocolate under resting conditions may be attributed to improved nitric oxide bioavailability, prostacyclin increase, direct effect of chocolate in smooth muscle cells, or activation of central mechanisms.”

And so, there are many unanswered questions about chocolate: What is the optimal dose of dark chocolate? How high does the cocoa content need to be to offer health benefits? Who in the population stands to benefit from eating dark chocolate? Are the benefits of liquid cocoa and solid chocolate the same? Can people eat chocolate without gaining weight?

When all is said and done, we could consider that these answers and others will come as time goes by. But for now, is it not delicious to think that indulgence and health may both reside beneath the same yummy wrapper?

References

• Blumberg J et al. Hypertension: Journal of the American Heart Association, June 2005, http://enews.tufts.edu/, http://hnrc.tufts.edu/scientists/people/blumberg.php
• Engler MB , Engler MM , Blumberg J et al. Flavonoid-rich dark chocolate improves endothelial function and increases plasma epicatechin concentrations in healthy adults, J Am Coll Nutr. 2004 Jun; 23(3):197-204.
• Human Nutrition Research Centre on Ageing, Tufts University Boston http://hnrc.tufts.edu/publications/
• RedNOVA News "Another Reason to Eat Chocolate-Blood Preassure" http://www.rednova.com/modules/news/tools.php?tool=print&id=178534
• Research Bites into Dark Chocolate Benefits, http://www.nbc13.com/health/4740985/detail.html,
  http://www.intelihealth.com/IH/ihtIH/WSIHW000/333/7228/368712.html.

Monika Bhatia
Project Manager and Editor

29 July 2005

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