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Harvard Study: Dark Chocolate Can Help Lower Your Blood Pressure

It also helps lower risk of diabetes, heart disease

spinner image Dark Chocolate is Good for You
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More good news for chocolate lovers: A new Harvard study finds that eating a small square of dark chocolate daily can help lower blood pressure for people with hypertension.

The study joins the growing research into the heart-healthy benefits of flavonoids, compounds in unsweetened chocolate that cause dilation of the blood vessels. The Harvard study was announced today in Atlanta at the American Heart Association's science session on cardiovascular disease.

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Defining Dark Chocolate


How much cocoa should it have to be healthy?

The U.S. Food and Drug Administration defines the categories of chocolate based on their content of cacao, or cocoa solids. The higher the percentage of cocoa solids, the more heart-healthy flavonoids the chocolate contains. To choose the healthiest dark chocolate, check the label: It should say the chocolate contains 60 to 70 percent cacao. These chocolates are often called bittersweet or extra bittersweet; they contain a small amount of sugar for flavor and a healthy amount of flavonoids. Here, then, is dark truth about chocolate:

Unsweetened chocolate: 100 percent cacao.

Bittersweet chocolate: 35 to 99 percent cacao; must contain at least 35 percent unsweetened chocolate and less than 12 percent milk solids; the broadest category, it can include products called bittersweet, semisweet, dark, extra dark or extra bittersweet.

Sweet chocolate: 15 to 34 percent cacao; must contain at least 15 percent unsweetened chocolate and less than 12 percent milk solids; sometimes also called dark chocolate, although it has a lower percentage of cocoa solids than bittersweet.

Milk chocolate: Contains at least 10 percent unsweetened chocolate, 12 percent milk solids, 3.39 percent milk fat.

The study analyzed 24 chocolate studies involving 1,106 people. It found that dark chocolate, the kind that contains at least 50 to 70 percent cocoa, lowered blood pressure in all participants, but most notably in those with hypertension. Eric Ding of Harvard Medical School and Brigham and Women's Hospital, a coauthor of the study, says researchers also found that chocolate increased insulin sensitivity, good for lowering diabetes risk.

Dark chocolate also appears to affect cholesterol. The Harvard researchers found some evidence for a small decrease in LDL (bad) cholesterol and a significant increase in HDL (good) cholesterol. Triglycerides, however, were unchanged.

As the researchers write, there is "rather strong evidence" that cocoa consumption improves several important cardiovascular risk factors "and likely reduces the risk of cardiovascular disease."

Research touting chocolate's health benefits has become increasingly popular in the past decade. While tea, fruits and vegetables also contain these heart-healthy compounds, "flavonoids are notably abundant in the cocoa solids of the cocoa bean," the study's authors write.

Chocolate with a higher proportion of cocoa solids — like unsweetened or dark chocolate — will contain more flavonoids. Dark chocolate, for example, contains from 46 to 61 mg of catechin, a type of flavonoid, in 100 grams (about one ounce), while milk chocolate contains only 15 to 16 mg, the study notes.

Obviously, encouraging people to eat dark chocolate for its health benefits is appealing advice, and older Americans have taken it to heart. Men and women age 55 and over now make up the bulk of dark chocolate consumers, according to the latest figures from market research firm Mintel.

In a May 2008 survey of consumers who bought chocolate for themselves in the past year, two-thirds of those 55-plus said they chose dark chocolate. Among those 65 and older, the preference for dark was even higher — nearly 75 percent. But Ding and his team caution that commercial processing plus the added sugar in the average dark chocolate bar can counteract a big chunk of its benefits.

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Other studies have suggested that "modern manufacturing of chocolate may induce losses of more than 80 percent of the original flavonoids from the cocoa beans," the researchers report, and the added sugar can contribute to weight gain, which can increase a person's risk of cardiovascular disease and diabetes.

The best advice is moderation — plus choosing chocolate with the lowest amount of sugar and the highest amount of cocoa. For those who want their little square of dark chocolate to pack the highest concentration of flavonoids, Ding recommends choosing brands that are "at least 70 percent cocoa."

Whether eating a little dark chocolate every day is a good long-term strategy for cardiovascular health, Ding says it's too soon to tell. "More research is needed," he says, to be sure the weight gain risk doesn't outweigh the benefits to your heart.

Candy Sagon writes about health and nutrition for the AARP Bulletin.

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