Watermelon Fruit by Ray Sahelian, M.D. (Citrullus lanatus, Family Cucurbitaceae) Watermelon fruit health benefit

Watermelon is the fruit and plant of a vine-like (climber and trailer) herb originally from southern Africa. The watermelon fruit, loosely considered a type of melon (although not in the genus Cucumis), has a smooth exterior rind (green and yellow) and a juicy, sweet, usually red or yellow interior flesh. Watermelon is rich in lycopene, an antioxidant that makes watermelons and tomatoes red and may help reduce heart disease and some cancers. The lycopene content of watermelon is substantial, contributing 8-20 mg per 180 gram (about 6 ounce) serving.

   You can buy a Lycopene supplement here. The temperature at which watermelon is stored influences the lycopene content (see below). Citrulline is a substance related to arginine and is found in high concentrations in watermelon rind. Some claim citrulline has similar effects to Viagra. Is it? See citrulline for more information.

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Nutritional content of watermelon
Watermelon is a great source of vitamin C and a good source of vitamin A, notably through its concentration of beta-carotene. Watermelon is also a source of the potent carotenoid antioxidant, lycopene. Vitamin C, beta carotene and lycopene are potent free radical scavengers. Watermelon has small amounts B vitamins, iron, and potassium, and very small amounts of calcium and magnesium. Watermelon is mostly carbohydrate with little protein and hardly any fat or cholesterol.

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Calorie content of watermelon
A whole cup (about 8 ounces) of watermelon contains about 40 to 70 calories since about 90 percent of watermelon fruit is water.
 

Storing Watermelon
Watermelons stored at room temperature deliver more nutrients than refrigerated or freshly picked melons. Researchers tested several popular varieties of watermelon stored for 14 days at 70 F, 55 F and 41 F. Whole watermelons stored at 70 degrees Fahrenheit, which is about room temperature in air-conditioned buildings, had substantially more nutrients. Compared with freshly picked fruit, watermelon stored at 70 F gained up to 40 percent more lycopene and 50 percent to 139 percent extra beta-carotene, which the body converts to vitamin A. Watermelons continue to produce these nutrients after they are picked and that chilling slows this process. The usual shelf life for watermelons is 14 to 21 days at 13 degrees Celsius (55 F) after harvest. At refrigerated temperatures, such as 41 F, watermelon starts to decay and develop lesions after a week.
 

Carotenoid changes of intact watermelons after storage.
J Agric Food Chem. 2006 Aug 9;54(16):5868-74. Perkins-Veazie P, Collins JK. South Central Agricultural Research Laboratory, Agricultural Research Service, US Department of Agriculture, Lane, Oklahoma 74555, USA.
Three types of watermelon, open-pollinated seeded, hybrid seeded, and seedless types, were stored at 5, 13, and 21 degrees Centigrade for 14 days and flesh color, composition, and carotenoid content were compared to those of fruit not stored. Watermelons stored at 21 degrees C had increased pH, chroma, and carotenoid content compared to fresh fruit. Compared to fresh fruit, watermelons stored at 21 degrees C gained 11-40% in lycopene and 50-139% in beta-carotene, whereas fruit held at 13 degrees C changed little in carotenoid content. These results indicate that carotenoid biosynthesis in watermelons can be affected by temperature and storage.
 

Watermelon and feta cheese
Watermelon is a delicious fruit dessert when eaten with feta cheese. Feta cheese seems to be the best type of cheese to eat with watermelon due to its crumbling capacity and the fact that it is salty. In the Middle East, many people eat watermelon with feta cheese. Officially watermelon is classified as a vegetable.

Varieties of watermelon
There are close to 200 varieties of watermelon grown in the United States. These are classified into four general groups: Picnic, Ice-box, Yellow Flesh, and Seedless.

Watermelon is a good source of citrulline
Watermelon (Citrullus vulgaris Schrad.) is a natural and rich source of the non-essential amino acid citrulline. Citrulline is used in the nitric oxide system in humans and has potential antioxidant and vasodilatation roles.

Watermelon consumption increases plasma arginine concentrations in adults.
Nutrition. 2007 Mar;23(3):261-6. USDA-ARS, South Central Agricultural Research Laboratory, Lane, Oklahoma, USA.
Watermelon is a rich source of citrulline, an amino acid that can be metabolized to arginine, a conditionally essential amino acid for humans. Arginine is the nitrogenous substrate used in the synthesis of nitric oxide and plays an essential role in cardiovascular and immune functions. This study investigated if watermelon juice consumption increases fasting concentrations of plasma arginine, ornithine, and citrulline in healthy adult humans. Subjects consumed a controlled diet and 0 (control), 780, or 1560 g of watermelon juice per day for 3 wk in a crossover design. The treatments provided 1 and 2 g of citrulline per day. Treatment periods were preceded by washout periods of 2 to 4 wk. Compared with the baseline, fasting plasma arginine concentrations increased 12% after 3 wk of the lower-dose watermelon treatment; arginine and ornithine concentrations increased 22% and 18%, respectively, after 3 wk of the higher-dose watermelon treatment. Fasting citrulline concentrations did not increase relative to the control but remained stable throughout the study. The increased fasting plasma concentrations of arginine and ornithine and stable concentrations of plasma citrulline in response to watermelon juice consumption indicated that the citrulline from this plant origin was effectively converted into arginine.

Dietary supplementation with watermelon pomace juice enhances arginine availability and ameliorates the metabolic syndrome in Zucker diabetic fatty rats.
J Nutr. 2007 Dec;137(12):2680-5. Faculty of Nutrition and Department of Animal Science, Texas A&M University, College Station, TX 77843, USA.
Pomace is the solid remains of olives, grapes, watermelon or other fruit after pressing for juice or oil. It is essentially the pulp, peel, seeds and stalks of the fruit after the oil, water, or other liquid has been pressed out. Watermelon is rich in L-citrulline, an effective precursor of L-arginine. This study was conducted to determine whether dietary supplementation with watermelon pomace juice could lessen the metabolic syndrome in the Zucker diabetic fatty rat, an animal model of noninsulin-dependent diabetes mellitus. Nine-week-old rats were assigned randomly to receive drinking water containing 0% (control) or 0.2% L-arginine (as 0.24% L-arginine-HCl), 63% watermelon pomace juice, 0.01% lycopene, or 0.05% citrus pectin. At the end of the 4-wk supplementation period, blood samples, aortic rings, and hearts were obtained for biochemical and physiological analyses. These results provide the first evidence to our knowledge for a beneficial effect of watermelon pomace juice as a functional food for increasing arginine availability, reducing serum concentrations of cardiovascular risk factors, improving glycemic control, and ameliorating vascular dysfunction in obese animals with type-II diabetes.

Do watermelons have effects similar to Viagra?
The media has made a big story of watermelon having Viagra-like effects since watermelons contain a substance called citrulline which converts into the amino acid arginine. Arginine helps dilate blood vessels. Because of this biochemical connection, Bhimu Patil, a researcher and director of Texas A&M's Fruit and Vegetable Improvement Center was quoted saying, "Arginine boosts nitric oxide, which relaxes blood vessels, the same basic effect that Viagra has, to treat erectile dysfunction and maybe even prevent it." Well, this is all the media needed to hype this story. But, does eating watermelon flesh or rind have any sexual enhancing effects? I love watermelon, it is one of my favorite foods. I actually love the combination of watermelon and feta cheese. I have been known to eat half a large watermelon at one sitting. I have not noticed any Viagra-like effects from eating watermelon or drinking watermelon juice. I have also tried citrulline supplements and arginine supplements and have not noticed much of an effect on erectile function. Even if citrulline and arginine dilate blood vessels, their effects are brief. If you really want to enhance libido, sensation and sexual stamina, Passion Rx with Yohimbe is one of your best options. 
   According to Bhimu Patil, more citrulline - about 60 percent - is found in watermelon rind than in the flesh.