The juice has long had a reputation amongst athletes, but now scientists have found evidence that it can relieve post-exercise muscle soreness.
One of the naturally occurring chemicals found in the fruit accelerates lactic acid removal, allowing better physical performance as the athlete can carry out more intense training and is able to recover faster after each workout, it is said. The report, published in the Journal of Agricultural and Food Chemistry, attributes watermelon's effects to the amino acid L-citrulline.
“Watermelon juice, naturally rich in l-citrulline, is an excellent option for athletes who want to improve their sports performance,” the authors say. Their study confirms previous findings that the fruit can improve athletic ability. The acid is an essential compound in nitric oxide, a gas that widens the blood vessels, and previous studies have also found that a daily dose of watermelon could lower blood pressure, reducing the risk of a stroke or a heart attack.
Researchers from the Technical University of Cartagena, in Spain, gave volunteers either natural watermelon juice, watermelon juice enriched with the amino acid, or a placebo an hour before exercise.
They then tested recovery and found both types of the watermelon juice “helped to reduce the recovery heart rate and muscle soreness after 24 hours”, although the natural juice was more easily digested by the body.
“Other benefits associated with l-citrulline intake include improving athletic performance,” the authors wrote.
This is because it helps with nitric oxide synthesis and increases the glucose transport in skeletal muscle, they explained. The findings may mean that natural ingredients could be used instead of drugs, they hope, suggesting future research should look at the levels of the amino acid required "for reduction of muscle fatigue and other health benefits in stress, athletic performance, and cardiovascular disease".
“Functional compound contents in fruits and vegetables play a key role in the design of new natural and functional products (beverages, juices, energy bars, etc.) by the food industry instead of synthetic compounds from pharmaceutical industry,” the authors concluded.