Watermelon Juice for Muscle Recovery: How L-Citrulline and Natural Electrolytes Work Together

Why Watermelon Gets Attention

Watermelon is one of the richest food sources of L-citrulline, an amino acid the body converts into L-arginine, a building block for nitric oxide. Nitric oxide helps blood vessels relax, which is why citrulline has been studied for exercise performance and recovery.

How Much Citrulline Is in Watermelon?

A USDA analysis of watermelon varieties (Rimando & Perkins-Veazie, Journal of Chromatography A, 2005) found citrulline in red flesh at about 1.9 mg per gram of fresh fruit and in the rind at about 1.3 mg per gram fresh weight. The rind contained more on a dry-weight basis, but on a fresh basis the flesh actually had slightly more. Content also varied by variety and flesh color.

For a sense of scale, the natural watermelon juice used in a Spanish study provided 1.17 g of citrulline in 500 mL (Tarazona-Díaz et al., 2013) — roughly 0.5 g in a 240 mL glass.

What the Studies Found

Soreness after a hard test. In that study (Tarazona-Díaz et al., Journal of Agricultural and Food Chemistry, 2013), seven athletes drank 500 mL of natural watermelon juice, citrulline-enriched watermelon juice or a placebo before a maximal cycling test. Both watermelon juices reduced recovery heart rate and muscle soreness 24 hours later. In lab tests of gut-cell absorption, citrulline was more available from unpasteurized juice than from heat-treated juice or pure citrulline.

Enriched juice and muscle-damage markers. In a double-blind crossover trial in 19 healthy men performing heavy half-squats (Martínez-Sánchez et al., Journal of Agricultural and Food Chemistry, 2017), watermelon juice enriched with extra citrulline and pomegranate ellagitannins kept blood markers of muscle damage near baseline, helped maintain force and reduced perceived exertion and soreness. Note that this was an enriched product, not plain juice.

Watermelon vs a sports drink during long rides. Twenty trained cyclists completed 75 km time trials while drinking either watermelon purée or a 6% carbohydrate drink (Shanely et al., Nutrients, 2016). Performance did not differ. Watermelon raised blood citrulline, arginine, nitrate and antioxidant capacity, but did not change post-exercise inflammation or immune markers — and perceived exertion was not better with watermelon.

Citrulline supplements more broadly. A meta-analysis of 13 randomized trials with 206 participants (Rhim et al., Journal of Sport and Health Science, 2020) found citrulline supplements reduced perceived exertion and muscle soreness at 24 hours, but not blood lactate. The most common dose was 8 g of citrulline malate — several times what a glass of natural juice provides. A broader review (Gonzalez & Trexler, Journal of Strength and Conditioning Research, 2020) noted that citrulline raises blood arginine and nitric oxide markers, but evidence that it actually improves blood flow to muscle is scarce and inconsistent.

Electrolytes: Good Potassium, Very Little Sodium

According to USDA food composition data, raw watermelon provides roughly 110 mg of potassium per 100 g (about 170 mg in a cup of diced fruit) but only around 1 mg of sodium per 100 g. Sweat losses are mostly sodium. The American College of Sports Medicine (2007) notes that drinks containing electrolytes and carbohydrate can help in some situations — for example long sessions or heavy sweating in heat — and that sweat rates and sodium losses vary widely between people.

So watermelon juice can contribute fluid, carbohydrate and potassium, but it is not a full electrolyte replacement for long, sweaty sessions. In those cases, add salty food or a sodium-containing drink.

How to Use It Sensibly

• Timing: The studies gave juice before exercise; some people prefer it afterward. Either is fine for most healthy people.
• Amount: A glass (about 250 mL) is a reasonable serving. The soreness benefits in supplement studies used much higher citrulline doses, so manage expectations.
• Fresh vs processed: Lab data suggest unpasteurized juice may offer more available citrulline, but freshly made juice should be refrigerated and used promptly for food safety.
• Whole fruit counts too: Whole watermelon gives the same citrulline and potassium plus more fiber.
• Fundamentals first: Adequate protein, carbohydrate, sleep and sensible training load matter far more for recovery than any single drink.

Who Should Be Careful

Watermelon juice contains natural sugar (about 6 g per 100 g of fruit), so people managing blood sugar should account for it. People with kidney disease who have been told to limit potassium should check with their care team. And if you're considering concentrated citrulline supplements, talk to a doctor or pharmacist first if you take blood-pressure medicines or nitrates.

The Bottom Line

Watermelon juice is a tasty, natural source of citrulline, potassium and carbohydrate, and small studies hint it may ease soreness. But plain juice delivers modest citrulline doses, its effects on blood flow are uncertain, and it is very low in sodium. Enjoy it as part of a recovery routine — not as a replacement for the basics.