Researchers at Texas A&M found in a recent study is that watermelon contains, along with lycopene, other phytonutrients that boost the body. One recent discovered phytonutrient in watermelon is citrulline. When citrulline is consumed, it converts to the amino acid arginine in the body through the work of selected enzymes. Arginine has long been linked to improved heart and immune function and shows promise as a way to offset Type 2 diabetes.