Eating watermelon may be protective against heart disease, prostate cancer, and dangerous free-radical damage in the body. Lycopene, the phytochemical associated with reduced prostate cancer risk and lower rates of heart disease, is the red pigment that gives watermelons their color. It is also a powerful antioxidant, scavenging aggressive chemicals that react with cell components that cause damage and loss of proper cellular function Watermelon contains about 40 percent more lycopene that tomatoes. Although lycopene levels vary among different types of melons, the seedless ones tend to have more, depending on both variety and growing conditions. Watermelon also contains the vitamins A, B6, C, and thiamin. A cup and a half of watermelon contains about 9 to 13 mg of lycopene. Red, ripe flesh is the best indicator of the sweetest and most nutritious watermelon. Other good sources of lycopene include tomatoes, red and pink grapefruit, red-fleshed papaya, and guava.