I came across a study involving watermelon juice extract (more on that later) and its effect on arterial stiffness and two others on their effects on endurance performance. It got me thinking of how many single-food- superfoods we’ve seen over the years and their supposed influence on some performance elements. As athletes, we are always looking for the ‘next great thing’ the “unknown-until-now” magic ingredient that will turn a mediocre triathlete into a champion.
What is it about human nature that we lean towards the small while stepping over the obvious? Don’t get me wrong; I love science. I love learning new things and finding out new ways to enhance performance. Around this time of year, I see athletes buying the latest fad supplements, upgrading their bike components, and setting lofty nutrition goals in favour of getting enough sleep, consuming enough protein and being consistently good at ingesting enough fruit and veg. Do we favour bedazzled over basic? Why are we ignoring the elephant in the room? Now back to that watermelon juice study. A group of 12 “healthy” young women (three cheers for a study that involves females) were tested under two conditions.
(a) one test gave each participant 90g of wild watermelon extract,
(b) one gave them a control beverage – a placebo.
They measured arterial stiffness, blood flow, and plasma nitrate at 30, 60, and 90 minutes. In all categories – there were improvements over the placebo. It showed that acute ingestion reduced lower-limb arterial stiffness. Aka… less sore in the legs… a nice thing after a hard brick session.
Two conflicting studies examined the hypothesis that watermelon juice supplementation would improve nitric-oxide bioavailability and exercise performance.
(a) The first one used 8 “healthy recreationally-active” adult males who were given 300ml a day of watermelon juice concentrate or apple juice concentrate as the placebo. Time to exhaustion was not significantly different. It increases resting blood pressure. The findings did not support using watermelon juice as a nutritional intervention.
(b) The other study out of Spain tested 19 “young” men by giving them 200ml watermelon juice enriched with L-citrulline and pomegranate ellagitannins over seven days. Perceived level of exertion went down. Exercise performance went up. It’s important to note that the Spain study added L-citrulline and pomegranate extract to boost the juice. I’d argue the magic came from the L-citrulline.
Watermelon juice naturally contains L-citrulline (0.5 g/200 mL) – the study boosted it to (3.3g/200ml). L-citrulline is a non-essential amino acid that can reduce the accumulation of lactic acid in the blood and has been shown to allow for higher levels of exercise resistance performance to exhaustion. L-citrulline is also an important component of the liver urea cycle responsible for detoxifying ammonia into urea. In addition, L-citrulline is a precursor to arginine. This amino acid can be converted to nitric oxide, a potent vasodilator that could increase blood flow and exercise performance.
So, what’s the takeaway, and why am I bringing all this up… so often these days, we will see “the latest” news and random “grand new supplements” being pushed and promoted on social media. Companies trying to sell you something often find influencers (or pro athletes) to support and advertise their products. Watermelon juice may be great but L-citrulline is better. Part of my job here at Fuelin is to dig through research and social media bullshit and help you decipher fact from fiction. There is more to be studied on watermelon juice extract/concentrate. I think we are learning about the real power of food more and more every day. We also know that we have substantial evidence to support tart cherry juice and Omega 3 fatty acids speeding up post-exercise recovery.
I would advise eating watermelon in season, especially after long hot training sessions (super high water content, low in calories and sweetly delicious). Get your Omega 3’s in daily and have some tart cherry juice in the fridge for hefty training blocks. Look at L-citrulline as an ergogenic aide but do not prioritise it above nailing your everyday nutrition.
 Fujie S, Iemitsu K, Inoue K, Ogawa T, Nakashima A, Suzuki K, Iemitsu M. Wild Watermelon-Extracted Juice Ingestion Reduces Peripheral Arterial Stiffness with an Increase in Nitric Oxide Production: A Randomized Crossover Pilot Study. Nutrients. 2022 Dec 7;14(24):5199. doi: 10.3390/nu14245199. PMID: 36558358; PMCID: PMC9780996.
 Bailey SJ, Blackwell JR, Williams E, Vanhatalo A, Wylie LJ, Winyard PG, Jones AM. Two weeks of watermelon juice supplementation improves nitric oxide bioavailability but not endurance exercise performance in humans. Nitric Oxide. 2016 Sep 30;59:10-20. doi: 10.1016/j.niox.2016.06.008. Epub 2016 Jul 1. PMID: 27378312.
 Martínez-Sánchez A, Alacid F, Rubio-Arias JA, Fernández-Lobato B, Ramos-Campo DJ, Aguayo E. Consumption of Watermelon Juice Enriched in l-Citrulline and Pomegranate Ellagitannins Enhanced Metabolism during Physical Exercise. J Agric Food Chem. 2017 Jun 7;65(22):4395-4404. doi: 10.1021/acs.jafc.7b00586. Epub 2017 May 26. PMID: 28513179.
 O'Connor E, Mündel T, Barnes MJ. Nutritional Compounds to Improve Post-Exercise Recovery. Nutrients. 2022 Nov 29;14(23):5069. doi: 10.3390/nu14235069. PMID: 36501099; PMCID: PMC9736198.