Microencapsulated watermelon rind serves as a bioavailable source of L-citrulline that produces plasma concentration increases comparable to those of purified L-citrulline supplements in healthy young adults, and its effects on vascular function are acute and limited to endothelial response.

When L-citrulline from watermelon rind is eaten, it enters the bloodstream and is turned into L-arginine in the kidneys. L-arginine is then used by blood vessel lining cells to make nitric oxide, which tells the muscle around the vessels to relax, allowing more blood to flow. This effect happens quickly and lasts about an hour before returning to normal.