No one food is a magic tonic for better health, but some pack a bigger nutritional wallop than others. These seven superfoods may not turn you into an action hero overnight, but they will deliver the vital antioxidants, vitamins, and minerals you need to stay buff, day in and day out. Tea  A cup a day can keep the cardiologist away, according to a recent study from Brigham and Women's Hospital in Boston. The study found that people who drink one or more cups of black tea each day were 44 percent less likely to suffer a heart attack than those who didn't sip. Tea is chock full of flavonoids…