Writer Mark Twain once said, “When one has tasted watermelon, he knows what angels eat.” Whether watermelon is heavenly is up for debate, but no question remains as to the nutritional value – it is high in vitamin C and serves as a source of vitamin A. Consuming watermelon may also have some unexpected side effects as well, some positive, some negative.
Including watermelon in your diet may trigger allergic reactions. Evidence available in the 2009 edition of “International Archives of Allergy and Immunology” reveals that the allergens in this fruit consist of malate dehydrogenase, triose phosphate isomerase and profiling, all of which are enzymes. You may experience an allergy to watermelon if you have allergic sensitivities to latex, celery, cucumber or carrot – the Allergen Bureau reports that these allergies are related. Watermelon allergy symptoms may range from mild to severe, including hives, facial swelling, diarrhea or anaphylaxis.
Eat a serving of watermelon, and you may see benefits to your blood pressure. Research in the January 2011 issue of “American Journal of Hypertension” correlates watermelon with improved blood flow through the aorta, the largest artery in the heart that carries blood from this organ to the rest of your body. This decreases blood pressure due to the citrulline in watermelon that converts to arginine – researchers note that arginine decreases blood pressure in the brachial artery. Do not consume watermelon as a method of hypertension treatment without consulting your health care provider.
The citrulline that contributes to lower blood pressure also relaxes your blood vessels according to researchers from Texas A&M's Fruit and Vegetable Improvement Center. As citrulline becomes arginine, it increases nitric oxide – this action mimics drugs that treat erectile dysfunction. Researchers theorize that eating watermelon may not only help treat medically-triggered erectile dysfunction, but also prevent its occurrence. Consider eating the rind of the watermelon – it contains more citrulline than the flesh; many people use the watermelon rind to make pickles and relish. Research is needed to confirm these findings, so speak to your physician for medically approved options to treat this condition.
Watermelon is a good source of lycopene, containing 6,889 micrograms per 1-cup serving of diced fruit. This compound gives watermelon its color. No recommended daily intake minimum exists, although a report in the March 1, 2013 issue of "Natural Medicine Journal" states that doses of only 5 to 10 milligrams significantly increased lycopene levels in the body. Lycopene may act as an antioxidant, which can stop free radical damage that may trigger cells to mutate in a cancerous manner. While studies offer inconclusive evidence, the lycopene in watermelon may slow the progression of cancer or prevent it.