About This Juice
Watermelon juice is the easiest case for juicing being genuinely cost-effective. At peak summer season in the U.S., a whole seedless watermelon runs $5–8, yielding 8–10 pounds of flesh after rind removal — enough for 10–12 sixteen-ounce glasses of juice at roughly $0.50–0.80 per glass. That's cheaper than any bottled cold-pressed juice and most concentrate-based juices. Use our Juice Price Calculator to track your exact cost per glass as produce prices shift through the season. It's also one of the more nutritionally interesting summer fruits, beyond its obvious hydration value.
L-Citrulline: The Compound That Makes Watermelon Distinctive
Watermelon is the richest common dietary source of L-citrulline, a non-essential amino acid found primarily in the flesh (and in even higher concentrations in the rind, which most people discard). USDA data puts L-citrulline content at approximately 150–250mg per 100g of watermelon flesh. A two-cup serving of watermelon provides roughly 300–500mg of citrulline.
Why does that matter? Citrulline is metabolized by the kidneys into L-arginine, which is then used by endothelial cells to produce nitric oxide (NO) via the enzyme endothelial nitric oxide synthase (eNOS). Nitric oxide causes vasodilation — relaxation of smooth muscle in artery walls — which reduces peripheral resistance and blood pressure. Citrulline is actually a more effective precursor to arginine than supplemental arginine itself, because arginine is extensively metabolized in the gut and liver before reaching circulation (the "arginine paradox"), whereas citrulline bypasses this first-pass effect.
A 2013 study published in the Journal of Agricultural and Food Chemistry by Tarazona-Díaz et al. found that watermelon juice supplementation (500ml/day containing approximately 1,000mg citrulline) significantly reduced muscle soreness 24 and 72 hours post-exercise in athletes compared to placebo. This was a small study (n=7) and should not be overstated, but it supports the biological plausibility of watermelon juice for exercise recovery through the citrulline → arginine → NO pathway. Larger trials are needed for firm clinical recommendations.
Lycopene: Present, but Mostly in the Rind
Watermelon is one of the best dietary sources of lycopene, a carotenoid that gives red and pink produce its color. Per 100g, watermelon contains approximately 4.5–6.8mg of lycopene — more than raw tomatoes (2.6mg/100g), though less than cooked tomato products. Lycopene is associated with reduced prostate cancer risk in epidemiological studies (a 2004 review in the Journal of Nutrition by Giovannucci noted an inverse association), though causal evidence remains limited.
Important practical note: lycopene absorption from food is significantly higher when consumed with dietary fat (it's a fat-soluble carotenoid). Plain watermelon juice without any fat co-ingested will have lower lycopene bioavailability than watermelon eaten with, say, feta cheese or olive oil in a salad. If lycopene is specifically your goal, pair the juice with a meal containing fat rather than drinking it alone. This doesn't make the juice pointless — you still absorb some lycopene, and the citrulline and hydration benefits are unaffected by fat — but it's worth knowing.
Cucumber: Silica, Hydration, and Mild Flavor Balance
Cucumber is approximately 96% water, making it the highest-water vegetable you can juice. Its flavor is mild and slightly cooling, which complements watermelon without competing. English and Persian cucumbers have thinner skins that juice well; waxed standard cucumbers sold in many supermarkets should be peeled before juicing (the wax is food-safe but adds a waxy, off-note flavor to juice).
Cucumber skin contains meaningful amounts of silica (silicon dioxide), which plays a role in collagen synthesis and connective tissue integrity. The research on dietary silica is less developed than on other minerals — most studies use orthosilicic acid supplements rather than food sources — but leaving the skin on for untreated cucumbers adds both silica and additional potassium and magnesium relative to peeled flesh alone.
The Salt Addition: Why It Works
A pinch of flaky sea salt in watermelon juice sounds counterintuitive but has a real effect: small amounts of sodium enhance sweetness perception by suppressing bitterness receptors on the tongue, a well-documented psychophysical phenomenon. It also makes the drink more electrolyte-complete — watermelon and cucumber are high in potassium and magnesium but low in sodium, so adding a small amount (100–150mg sodium) better approximates the electrolyte profile needed for genuine rehydration during or after exercise. This is why sports drinks contain sodium despite tasting sweet.
Juicing Technique
Watermelon is almost entirely liquid, which means it overwhelms a centrifugal juicer's basket quickly. Feed it in small batches rather than continuously loading the chute. A masticating juicer also works but is slower; for watermelon, a centrifugal machine or even a blender plus straining through a nut milk bag is perfectly adequate. The flesh is so high in water that extraction efficiency differences between juicer types matter less than with fibrous produce like celery or leafy greens — see our Juice Yield Calculator for a comparison of yield rates across different produce types.
Remove seeds from seeded watermelon varieties before juicing — the seeds can jam masticating juicers and contribute a slightly bitter note to centrifugal juice if ground up. Seedless varieties eliminate this concern entirely. Feed the cucumber through with the skin on (if untreated) and alternate with watermelon to help push the lighter flesh through the feed chute.
Storage and Seasonal Timing
Watermelon juice is best consumed immediately — the foam settles within minutes and the flavor is brightest fresh. If storing, refrigerate in a sealed container and consume within 6–8 hours; potassium and vitamin C degrade relatively slowly but the fresh flavor fades noticeably by 24 hours. Do not freeze — ice crystal formation ruptures cell structure and the thawed juice is watery and flat.
Seasonal window: watermelon peaks July through mid-September in most of the U.S. Buying outside this window means either imported watermelon (higher price, lower sugar content due to early harvest) or domestic hothouse grown. The off-season price premium — often $8–12 for a small watermelon vs. $5–6 in July — is worth factoring into your cost-per-glass calculation. This recipe is designed as an in-season summer staple, not a year-round daily driver.