Several recent large-scale research reviews have provided the best evidence yet that chocolate, derived from the seeds of the cocoa tree (Theobroma cacao), is good for your heart.
In one review, in the British journal BMJ in August, researchers analyzed data from seven observational studies, which included more than 100,000 people. Those who ate the most chocolate had a 37 percent lower risk of heart disease, compared to those eating the least, after controlling for weight, physical activity, education and other dietary factors that could influence the results. They were also 29 percent less likely to have a stroke.
In a second review, in the European Journal of Clinical Nutrition in August, Harvard researchers looked at 10 clinical studies from the last decade, with a total of 320 people. Consuming dark chocolate or cocoa products for 2 to 12 weeks modestly lowered cholesterol. And another review of clinical trials, in BMC Medicine, found that cocoa-rich products had a small blood-pressure-lowering effect in people with hypertension and prehypertension.
Behind the benefits
Chocolate’s health benefits are largely attributed to polyphenol compounds called flavonoids—the same family of substances that are in tea, red wine, grape juice and other plant foods—which have antioxidant, anti-inflammatory and anti-clotting properties. In particular, flavonoids increase production of nitric oxide, which helps relax and dilate blood vessels, and this may help lower blood pressure and have other cardiovascular effects. Cocoa flavonoids may also inhibit cholesterol absorption as well as oxidation of LDL (“bad”) cholesterol, making it less harmful.
But before you reach for a chocolate bar, there are some caveats. First, not all studies have had positive results. And many—including all of those in the recent BMJ analysis—are observational studies, meaning that they don’t prove cause and effect (that chocolate, rather than something else about chocolate eaters, is responsible for the benefits seen).
Moreover, no one knows what type or amount of chocolate is optimal. Studies have used different formulations (with widely varying flavonoid levels) and intakes (from tiny daily amounts to impractically large quantities); some have not distinguished between milk and dark chocolate. Chocolate may affect people differently, too, depending on a variety of factors.
Keep in mind also that the chocolate confections that Americans love most are loaded with sugar, fat and calories (235 in a typical 1.5-ounce bar). Many have caramel, nougat and other unhealthy fillings and ingredients. Eat too much of any kind of chocolate and you can gain weight, which would likely cancel out the heart benefits.
• Not all chocolate is created equal. Processing of cocoa beans into commercial chocolate candy greatly reduces flavonoid levels. In fact, a main manufacturing objective is to remove these compounds because they have a bitter taste. Some companies use—or claim to use—methods that better preserve the heart-healthy compounds.
• Dark chocolate generally has more flavonoids than milk chocolate, but it’s hard to know how much a particular bar has. The percent cocoa (or cacao) listed on a label is not a reliable indicator of flavonoid content, and a bar that is, say, 70 percent cocoa from one manufacturer is not necessarily better than one that is 60 percent from another manufacturer. In addition to processing, the type of cocoa beans used and the manufacturer’s “recipe” also play a significant role in determining final flavonoid content. At the very least, the darker the chocolate, as indicated by a higher percent of cocoa solids, the less room there is for sugar.
• Though chocolate is high in saturated fat (from cocoa butter), this is mostly stearic acid, which has a neutral effect on blood cholesterol. On the other hand, milk chocolate has added fats that are not good for your heart, as well as more added sugar than dark chocolate. Milk chocolate has twice as much sugar as the darkest chocolate.
• Cocoa powder is highest in cocoa solids and has the most flavonoids—though “Dutch” (or alkali) processing destroys them. If you use cocoa powder, look for unsweetened natural versions. Next highest in flavonoids is unsweetened baking chocolate.
• Chocolate contains small amounts of caffeine—about 20 milligrams in an ounce of dark chocolate, and 6 milligrams in milk chocolate (compared to about 100 to 150 milligrams in a cup of coffee).
• It’s not clear whether adding milk to cocoa interferes with the absorption of flavonoids. A 2009 study in the American Journal of Clinical Nutrition, for instance, found reduced flavonoid absorption when people drank cocoa made with milk compared to cocoa made with water. Still, other studies have found no effect of milk on cocoa flavonoids and no difference in blood antioxidant levels. It’s possible that milk interferes with some, but not all, cocoa flavonoids. Some studies that found no milk interactions used cocoa with much higher flavonoid levels than those in commercial cocoa, which could make any flavonoid-reducing effect of the milk less apparent.
Chocolate may provide some heart-health benefits, especially if you eat it in place of other snacks or desserts that are high in calories and saturated fat. Choose the darkest chocolate that you like. Cocoa beans or some variation, such as cacao, chocolate liquor or cocoa mass, should be the first ingredient, not sugar. But even if it’s rich in flavonoids, think of chocolate as a treat, not a health food, because of its hefty calories. Fruits and vegetables are a better source of flavonoids on a daily basis—they have fewer calories and an abundance of vitamins and minerals, along with other healthy plant compounds and fiber.