"Guava has a higher concentration of lycopene—an antioxidant that fights prostate cancer—than any other plant food, including tomatoes and watermelon. In addition, 1 cup of the stuff provides 688 milligrams of potassium, which is 63 percent more than you'll find in a medium banana. And guava may be the ultimate high-fiber food: There's almost 9 grams of fiber in every cup."