The health benefits of dark chocolate are widely known—especially its effect on your heart.

The health benefits of dark chocolate are widely known—especially its effect on your heart. But new research is finding that chocolate may help boost your performance. Here’s what you need to know before breaking off a square (or two). Go Dark For Your Heart Studies have found that a daily square of dark chocolate can improve your heart health thanks to its flavanols, which serve as antioxidants. One study from 2010 showed that a small dose of dark chocolate could decrease your risk of heart attack and stroke by nearly 40 percent. But it matters what type of dark chocolate you nibble on. For the heart health benefits, reach for at least 70 percent cacao, which is fairly bitter without the added fat and sugar. And don’t forget that even though dark chocolate is considered a (somewhat) healthy treat, it still packs plenty of calories. A 100-gram bar of 85 percent dark chocolate, for example, clocks in around 600 calories, 450 of which come from fat. Minimal Processing, Better Performance New research is finding that chocolate—even at lower percentages of cacao than is normally recommended—may have a performance-boosting effect. Recent U.K. research shows that epicatechin, an antioxidant found in the cacao (cocoa) bean, may have slight performance benefits. The study, while small, showed that cyclists who consumed 40 grams of dark chocolate (Dove, in this case) a day displayed slight improvements in distance compared to their performance after consuming white chocolate. White chocolate is highly processed, which means it’s lost most, if not all, of its epicatechin. “The more chocolate is processed the more antioxidant flavonols, including epicatechin, are lost,” said Monique Ryan, M.S., R.D.N., the author of Sports Nutrition for Endurance Athletes. Dove dark chocolate has high levels of epicatechin, study co-author Rishikesh Patel told Runner’s World by email. And a 2004 study in the Journal of the American College of Nutrition found it to improve blood flow in arteries. But Dove dark chocolate is relatively low in cacao—only 53 percent. Which poses the question, does cacao percentage matter when it comes to performance? Patel and colleagues are currently analyzing different levels of flavanols in chocolate to measure their effectiveness on exercise. But the results won’t be out until next year. The Takeaway The more processed the chocolate, the less of the good stuff (heart-healthy antioxidants and epicatechin) there is. So while Patel’s study found you may be able to to get a small performance benefit from the sweeter-tasting Dove dark chocolate, it’s more processed than other options that may be better for your heart, like cacao nibs. Nibs, available online and at gourmet grocery stores, are very close to the original, unprocessed bean, with a texture not unlike a coffee bean. “A higher cacao percentage will taste more bitter, so it really just depends on your taste preferences,” Ryan said. But whatever you do, choose dark over milk chocolate, which has more added sugar and fat. And while the participants of Patel’s study ate an entire 40-gram chocolate bar daily (1.4 ounces), Ryan suggests a smaller amount to keep your waistline in check. “I would keep it to half an ounce or one ounce per serving—just from a calorie perspective,” she said. Dove’s 40.8-gram dark chocolate bar is 220 calories and 13 grams fat.