Spinach, collards, mustard greens and turnip greens figure prominently in traditional African cuisine, which is a good thing since they make up the largest and healthiest tier of the new African Heritage Diet Pyramid. And no wonder! Besides being low in calories (one cup of mustard greens has 21 calories; a cup of spinach has only 7!), greens can boost cardiovascular health: A recent study published in the American Journal of Clinical Nutrition found that women who ate one serving of leafy greens per day were 46 percent less likely to develop heart disease than those who didn’t. Cooked lightly with healthy oils or steamed with water and lemon, greens are far more delicious than that limp, gray, slimy stuff the lunchroom ladies plunked on your plate in grade school.