Athletes finally have some proof to support the long-held belief that watermelon juice can reduce posttraining muscle soreness. The report in the American Chemical Society’s Journal of Agricultural and Food Chemistry (2013, 61 (31), 7522-28) attributes watermelon’s “healing” effects to the amino acid L-citrulline.

According to a press release, researcher Encarna Aguayo and colleagues cited past research on watermelon juice’s antioxidant properties and its potential to increase muscle protein and enhance athletic performance. But scientists had yet to explore the effectiveness of watermelon juice drinks enriched with L-citrulline. Aguayo’s team set out to fill that knowledge gap.

Volunteers drank natural watermelon juice, watermelon juice enriched with L-citrulline and a control drink containing no L-citrulline on volunteers an hour before exercise. Both the natural juice and the enriched juice relieved muscle soreness in the volunteers. But in the natural juice (unpasteurized), L-citrulline seemed to be more bioavailable—in a form the body could use better—the study found.