According to a new study published in Journal of food and agricultural chemistryDrinking watermelon juice before an intense workout helped reduce the athletes’ heart rate and muscle soreness the next day. This is because watermelon is rich in an amino acid called L-citrulline, which the body converts into L-arginine, an essential amino acid that helps relax blood vessels and improve circulation.

The seven study participants, all men, were given either 500ml of fresh watermelon juice, extra citrulline-rich watermelon juice, or a placebo drink one hour before training. It is interesting to note that the natural juice was just as effective as the enriched juice. The researchers also found that intestinal cells can absorb more citrulline from watermelon juice than from citrulline supplements, especially when the juice is not pasteurized.

Postmenopausal women showed improvements in cardiovascular health after six weeks of taking a commercially available watermelon extract supplement containing citrulline and arginine, according to a study published earlier this year by physiologist Arturo Figueroa of the University of Florida, USA.

And in a 2012 study also led by Figueroa, these supplements helped relieve high blood pressure in middle-aged obese adults.

Improved circulation can benefit more than just the heart, as at least one watermelon researcher has pointed out. But you’ll probably have to eat a lot to get the desired effect — and overeating can cause unfortunate side effects, as watermelon has long been known as a natural diuretic.

You might assume that watermelon has little nutritional value and is more than 90% water. But a 300ml slice of watermelon contains about a third of the recommended daily value of vitamins A and C, as well as a modest amount of potassium (9% of the daily value).

Watermelons are among the best dietary sources of lycopene, an antioxidant linked to the prevention and treatment of prostate cancer, although scientists are still researching the details of this connection.