By now, you’ve probably sipped beet juice, pressed turmeric root into shooters, guzzled post-run coconut water, and suffered through more lumpy green smoothies than you care to admit. When it comes to getting a competitive edge, we athletes take our literal juicing seriously.
Now a new “must-drink” juice may be about to make its way into our already-cluttered fridges. In May, the Journal of Applied Physiology published an article stating that L-citrulline supplementation could improve oxygen uptake (V02) and high intensity exercise performance in recreational athletes. While the study used L-citrulline tablets, in whole-food form, watermelon is the best natural source of L-citrulline—by a lot. (L-citrulline is derived from the Latin word for watermelon.)
Here’s how the study worked: Over a period of three seven-day cycles, ten recreational cyclists were given either L-citrulline, L-arginine, or placebo supplement tablets. On days six and seven, athletes completed both moderate and intense cycling tests. While there were no changes in performance with the L-arginine supplements, after taking the L-citrulline tablets the cyclists had improved VO2 kinetics, time-to-exhaustion, and max power during a 60-second all-out sprint.
Dr. Stephen Bailey, the lead researcher for this study, is the first to point out that more research needs to be done before athletes begin swigging watermelon juice. His study used recreational athletes, but the results could be very different in elite athletes, he says. The study’s sample size, just 10 athletes, was relatively small. Furthermore, researchers are only just beginning to study how L-citrulline can affect athletic performance—before recommendations are given, studies like this one need to be replicated to make sure the results are valid. “Other foods have quite small L-citrulline contents compared to watermelon,” Bailey says. However, “you'd need to drink about 2.5 liters of watermelon juice to get the same dose of L-citrulline used in this study, which might not be very practical.”
Still, these caveats haven’t stopped the watermelon industry from revving up its juicers.
Athletes have been a target market for melon growers for a while. A few years ago, at a meeting of the National Watermelon Association, the delegation from South Carolina—where many melons are grown—decided the industry should focus on getting slices of watermelon into collegiate athlete’s hands. “We knew that watermelon was this great source of L-citrulline, lycopene and potassium, but sending out slices was not logistically efficient,” says Hilary Long, director of development for Tsamma, a high-end watermelon juice company.
Tsamma’s juice has been slowly catching on with Instagram fitness celebs and the “fitfluential” crowd for free product, though no real pro athletes have come knocking yet. And really, Tsamma—which is named for the ancient melons that thrived in the arid deserts of Africa and are thought to be the ancestors of today’s watermelons—is still a tiny sliver of Frey Farm’s giant watermelon organization. But that could change.
“The buzz is definitely growing,” Long says. “I think watermelons are the coconut water of ten years ago.”