The risks for developing asthma are lower in people who consume a high amount of certain nutrients. One of these nutrients is vitamin C, found in many fruits and vegetables, including watermelon. Blood pressure A study published by the American Journal of Hypertension found that watermelon extract supplementation improved the health of the circulatory system in obese middle-aged adults with prehypertension or stage 1 hypertension. Diets rich in lycopene - found in watermelon - may help protect against heart disease. Cancer As an excellent source of antioxidants, including vitamin C, watermelon can help combat the formation of free radicals known to cause cancer. Lycopene intake has been linked with a decreased risk of prostate cancer in several studies. Digestion and regularity Watermelon, because of its water and fiber content, helps to prevent constipation and promote regularity for a healthy digestive tract. Hydration Made up of 92 percent water and full of important electrolytes, watermelon is a great snack to have on hand during the hot summer months to prevent dehydration. It can also be frozen in slices for a tasty cold Popsicle-style snack.