Big, sloppy slices of watermelon served at a picnic table are the quintessential summer snack—sweet enough to be dessert and good for our health as well. Given its name and the fact it is 90 percent water you might assume the fruit has little nutritional value, but only 300mL of watermelon packs in about one-third of the recommended daily value of vitamins A and C, as well as a modest amount of potassium. Drinking watermelon juice before a hard workout helps reduce athletes heart rates and next day muscle soreness. That's because watermelon is rich in amino acid that helps relax blood vessels and improve circulation. Improved circulation can benefit more than just the heart, it can be a natural Viagra too. But you'd probably have to eat an awful lot to achieve the desired effect-and eating too much could cause unfortunate side effects, since watermelon has long had a reputation as a natural diuretic.