Nutrients in Watermelon
Watermelon is a very good source of vitamin C, beta-carotene and lycopene. Watermelon is a good source of vatamins B1 and B6, pantothenic acid, biotin, magnesium, potassium and dietary fiber.

Prostate Cancer
Watermelon is a rich natural source of lycopene, a carotenoid of great interest because of its antioxidant capacity and potential health benefits. Dietary consumption of the carotenoid lycopene has been associated with a lower risk of prostate cancer. Data from studies provides evidence that increased consumption of lycopene-containing foods might reduce the occurrence or progression of prostate cancer.
The results of a study suggest that vegetables and fruits rich in lycopene and other carotenoids may be protective against prostate cancer. To determine whether dietary intake of lycopene and other carotenoids has an etiological association with prostate cancer, a study was conducted of 130 prostate cancer patients. The prostate cancer risk declined with increasing consumption of lycopene, alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein and zeaxanthin. Intake of tomatoes, pumpkin, spinach, watermelon and citrus fruits were also inversely associated with prostate cancer risk.

Immune System Booster
Watermelon is a rich source of citrulline, an amino acid that can be metabolized to arginine, an essential amino acid. A controlled human study investigated if watermelon juice consumption increases fasting concentrations of plasma arginine, ornithine, and citrulline in healthy adult humans. The results of the study demonstrated that plasma concentration of arginine could be increased through intake of citrulline from watermelon.
Arginine plays an important part in the healing of wounds and the removal of ammonia from the body. Excess ammonia in the blood can lead to fatigue, kidney and liver disease.
Arginine is the physiologic precursor in the synthesis of nitric oxide (NO), which plays a pivotal role in many biological processes such as platelet aggregation and immune system modulation. A study involving 40 children demonstrated an increase in lymphocytes, which play an important role in the immune system after oral administration of arginine.

Impotence
Arginine seems to improve sexual function in men with impotence. A study of 50 men with impotence reported significant improved sexual function after arginine supplementation.

Heart Health
The arginine that is available from watermelon has been shown to have beneficial effects in patients with heart failure.

Glycemic Index (GI)
Watermelon has a high glycemic index of 72 -80.