Watermelon juice: the lycopene arrives, most other promises did not

A 2025 meta-analysis of 15 randomized trials in 415 middle-aged and older adults found that L-citrulline supplements or watermelon lowered systolic blood pressure by 4.02 mmHg (95% CI 1.50 to 6.54) and diastolic by 2.54 mmHg (95% CI 0.81 to 4.27). It pooled citrulline pills with watermelon products and did not report juice separately. So that is not a juice number. What the juice does clearly is deliver lycopene. In a small controlled feeding study of 23 healthy adults aged 36 to 69, randomization not stated, 3 weeks of fresh-frozen watermelon juice raised plasma lycopene to 1078 nmol/L against 272 with no juice, about the level tomato juice reached. Doubling the dose did not raise it further. In a small 4-week trial in 16 postmenopausal women, two 12 fl oz (360 mL) glasses a day raised serum lycopene by 81% and changed nothing in cognition, oxidative stress or inflammation. Fresh juice that is not pasteurized is a food safety question, and FDA says untreated juice can cause serious illness in children, older adults, pregnant women and people with weakened immune systems.

As people eat it, per 3.5 oz (100 g)

How much is actually in it

• Two 12 fl oz (360 mL) servings a day of pasteurized 100% watermelon juice supplied about 14.4 mg lycopene in a trial beverage analysis. — trial beverage given to postmenopausal women, 720 mL per day for 4 weeks (n = 16) Evidence B source
  14.4 +/- 0.34 mg lycopene per day from 24 fl oz (720 mL), about 2 mg per 3.4 fl oz (100 mL)
• A 8.5 oz (240 g) serving of 100% watermelon juice gives about 72 calories and 14.9 g of sugars. — USDA survey food 64133100 Evidence E source
  30 calories and 6.2 g total sugars per 3.5 oz (100 g); 8.5 oz (240 g) serving 72 calories, 14.9 g sugars; 1 fl oz 30 g

What a real portion looks like

• The heart rate trial used 17 fl oz (500 mL) of watermelon juice a day for 2 weeks, roughly two US cups. — healthy adults aged 18-40 with BMI 18-29.9, no diabetes or watermelon allergy (n = 18) Evidence B source
  500 mL per day for 2 weeks, 2-week washout

What your body absorbs

• In a controlled crossover feeding study, 3 weeks of fresh-frozen watermelon juice raised plasma lycopene about four-fold, similar to tomato juice. — 23 healthy nonsmoking adults aged 36-69, 3-week periods on a controlled diet (n = 23) Evidence C source
  Plasma lycopene 1078 nmol/L on 20.1 mg/d from juice vs 272 nmol/L with no juice; doubling the dose gave 1183 nmol/L
• The same study found unheated watermelon juice delivered lycopene as well as canned tomato juice, and a double dose did not raise plasma levels further. — 23 healthy nonsmoking adults aged 36-69 (n = 23) Evidence C source
  No difference in plasma lycopene at week 3 between 20 mg/d and 40 mg/d watermelon juice or 18 mg/d tomato juice
• Watermelon eaten in quantity raised plasma citrulline markedly in six healthy adults, which can mimic a urea cycle disorder on metabolic tests. — a 19-month-old girl plus 6 healthy adult volunteers challenged with watermelon (n = 7) Evidence D source
  Plasma citrulline mean maximum 593 micromol/L (range 386-1069), arginine 199 micromol/L

What it does to your health

• In a crossover RCT on 18 healthy young adults, 2 weeks of daily watermelon juice blunted the fall in heart rate variability after a glucose drink. — 18 healthy young adults aged 18-40, 17 fl oz (500 mL) daily for 2 weeks, then a 75 g oral glucose challenge (n = 18) Evidence B source
  HF power preserved vs placebo (p = 0.03), pNN50 preserved (p = 0.009); no change in energy expenditure

Safety, limits and interactions

• FDA says children, older adults, pregnant women and people with weakened immune systems risk serious illness or even death from drinking untreated juice. Packaged untreated juice must carry a warning label, but juice sold by the glass, as at juice bars and roadside stands, does not need one. For juicing at home, FDA says to scrub melons with a clean produce brush and wash them even if they will be peeled. — children, older adults, pregnant women and people with weakened immune systems Evidence E source
  Untreated juice can cause serious illness or death in these groups; packaged untreated juice must carry a warning label, juice sold by the glass need not; scrub melons with a clean brush and wash before peeling or cutting
• For the watermelon used in juice, FDA advises scrubbing firm produce such as melons with a clean produce brush, buying pre-cut produce such as half a watermelon only if refrigerated or surrounded by ice, refrigerating all pre-cut or packaged produce, and storing perishable fruit at 40°F or below. — general public Evidence E source
  Scrub melon rind with produce brush, refrigerate pre-cut produce, store at 40°F or below
• A 1996 Singapore shipyard Salmonella outbreak with at least 116 ill workers was linked to watermelon juice and cut fruit washed with industrial water. — at least 116 shipyard workers, 27 bacteriologically confirmed cases (n = 116) Evidence C source
  Watermelon juice implicated (P < 0.01), cut watermelon (P < 0.001)

What people believe that the data does not support

• In an RCT on 22 adults, a single 24 fl oz (710 mL) dose of watermelon juice before exercise did not improve strength, endurance or VO2max. — 22 adults (11 men), 24 fl oz (710 mL) juice about 1.0 g citrulline, 1 or 2 h before testing (n = 22) Evidence B source
  No significant difference vs placebo in repetitions, time to exhaustion, VO2max, anaerobic threshold or FMD
• In an RCT on 15 resistance-trained men, 7 days of watermelon juice concentrate did not improve bench press or isometric strength. — 15 resistance-trained men, 22.4 +/- 2.9 years, concentrate with 2.2 g/day L-citrulline for 7 days (n = 15) Evidence B source
  No difference in performance, perception or vessel diameter; muscle oxygenation +4.1% vs placebo
• The EU refused a claim that citrulline-malate helps recovery from muscle fatigue, and it authorized no citrulline or lycopene claim. — EU health claim register Evidence E source
  Claim status non-authorized

Who this works differently for

• In an RCT on 16 postmenopausal women, 4 weeks of watermelon juice raised serum lycopene by 81% but did not change cognition or inflammation markers. — 16 postmenopausal women, 60 +/- 4.1 years, two 12 fl oz (360 mL) servings daily for 4 weeks (n = 16) Evidence B source
  Serum lycopene +81% (p = 0.002); no change in cognitive tests, oxidative stress or inflammation
• A meta-analysis of 15 RCTs found L-citrulline or watermelon intake lowered systolic blood pressure by about 4 mmHg in middle-aged and older adults. — middle-aged and elderly adults, 15 RCTs, 24 datasets, 415 participants (n = 415) Evidence A source
  SBP -4.02 mmHg (95% CI -6.54 to -1.50), DBP -2.54 mmHg (95% CI -4.27 to -0.81)

The bottom line

US survey data give 100% watermelon juice 30 calories and 6.2 g of sugars per 3.5 oz (100 g), so a 240 g glass carries about 72 calories and 14.9 g of sugars. One commercial pasteurized juice analyzed for a trial supplied 14.4 mg of lycopene in 24 fl oz (720 mL), about 2 mg per 3.4 fl oz (100 mL), and lycopene varies with cultivar and ripeness. We found no study comparing raw with pasteurized watermelon juice for any nutrient. The idea that watermelon juice improves exercise performance has been tested, and the trials found no effect. In 22 adults, a single 24 fl oz (710 mL) dose carrying about 1.0 g of citrulline, drunk 1 or 2 hours before testing, did not improve strength, endurance or VO2max against placebo. In 15 resistance-trained men, a concentrate with 2.2 g of citrulline a day for 7 days did not improve bench press or isometric strength. The EU refused a claim that citrulline-malate helps recovery from muscle fatigue, a refusal that means the evidence was judged insufficient at the time. In 18 healthy adults aged 18 to 40, 17 fl oz (500 mL) a day for 2 weeks preserved heart rate variability after a 75 g glucose drink better than placebo. The trial was small and short, measured a surrogate, and reported only p values (0.03 and 0.009) with no size of effect. Energy expenditure did not change. The one safety event we found was a food poisoning outbreak. In a 1996 Singapore shipyard outbreak, watermelon juice and cut watermelon were linked to Salmonella in at least 116 workers, 27 of them confirmed by laboratory, and the fruit had been washed with industrial water. The contamination came from that water, so how cut fruit and fresh juice are handled matters. FDA says children, older adults, pregnant women and people with weakened immune systems risk serious illness or even death from untreated juice, and juice sold by the glass, as at juice bars and roadside stands, needs no warning label. For juicing at home, FDA says to scrub melons with a clean produce brush and wash them even if they will be peeled. It also advises buying half a watermelon or other pre-cut produce only if refrigerated or surrounded by ice, refrigerating all pre-cut produce and storing perishable fruit at 40°F or below. Large amounts of whole watermelon also show up on lab tests. In 6 healthy adult volunteers, plasma citrulline peaked at a mean 593 micromol/L, and in a 19-month-old girl the same rise looked like a urea cycle disorder on metabolic testing. We found no data on the juice in pregnancy, kidney disease or alongside medicines, which is a gap rather than reassurance.

Sources

1. wmj-r8-03 · randomized crossover trial
   Following a one-week run-in period, participants were randomized to consume either two 360 mL servings of pasteurized 100% watermelon juice or an isocalorically-matched placebo beverage for four weeks. The mean daily provision of lycopene from the intervention juice was 14.4 ± 0.34 mg.
   J Nutr Gerontol Geriatr, 2021 · checked 2026-09-29
2. wmj-r8-13 · reference dataset
   FNDDS 2709333 Watermelon juice, 100%: Energy 30 kcal/100 g, Total Sugars 6.2 g/100 g · Quantity not specified 240 g 72.0 kcal 14.9 g sugars · 1 fl oz 30 g
   USDA FNDDS 2021-2023 · checked 2026-09-29
3. wmj-r8-06 · randomized crossover trial
   Subsequently, participants were randomized to complete 2 weeks of daily WMJ supplementation (500 mL) or a placebo drink (PLA).
   Nutrients, 2023 · checked 2026-09-29
4. wmj-r8-01 · controlled crossover feeding trial
   After 3 wk of treatment, plasma lycopene concentrations for the W-20, W-40, T-20 and C-0 treatments were (least squares means +/- SEM) 1078 +/- 106, 1183 +/- 139, 960 +/- 117 and 272 +/- 27 nmol/L, respectively.
   J Nutr, 2003 · checked 2026-09-29
5. wmj-r8-02 · controlled crossover feeding trial
   Plasma lycopene concentrations did not differ at wk 3 after W-20, W-40 and T-20 treatments, indicating that lycopene was bioavailable from both fresh-frozen watermelon juice and canned tomato juice, and that a dose-response effect was not apparent in plasma when the watermelon dose was doubled.
   J Nutr, 2003 · checked 2026-09-29
6. wmj-r8-11 · case report with volunteer challenge
   All developed markedly elevated plasma citrulline (mean maximum 593 micromol/L, range 386-1069) and moderately elevated plasma arginine (mean maximum 199 micromol/L, range 128-251).
   J Inherit Metab Dis, 2005 · checked 2026-09-29
7. wmj-r8-05 · randomized crossover trial
   WMJ supplementation preserved high-frequency power (HF) (treatment effect, p = 0.03) and the percentage of successive differences that differ by more than 50 ms (pNN50) (treatment effect, p = 0.009) when compared to the placebo treatment.
   Nutrients, 2023 · checked 2026-09-29
8. sf-juice-r6-1 · agency advice
   While most people’s immune systems can usually fight off the effects of foodborne illness, children, older adults, pregnant women, and people with weakened immune systems (such as transplant patients and individuals with HIV/AIDS, cancer, or diabetes) risk serious illnesses or even death from drinking untreated juices. ... These untreated products should be kept under refrigeration and are required to carry the following warning on the label: WARNING: This product has not been pasteurized and therefore may contain harmful bacteria that can cause serious illness in children, the elderly, and persons with weakened immune systems. However, FDA does not require warning labels for juice or cider that is sold by the glass – for example, at apple orchards, farmers’ markets, roadside stands, juice bars, and some restaurants. ... Scrub firm produce, such as melons and cucumbers, with a clean produce brush. Even if you plan to peel the produce before juicing it, wash it first so dirt and bacteria are not transferred from the surface when peeling or cutting into it.
   U.S. FDA, What You Need to Know About Juice Safety, content current as of 03/05/2024 · checked 2026-10-08
9. sf-melon-r1-wmjuice-2 · agency advice
   When buying pre-cut, bagged or packaged produce — such as half of a watermelon or bagged salad greens — choose only those items that are refrigerated or surrounded by ice...Store perishable fresh fruits and vegetables (like strawberries, lettuce, herbs, and mushrooms) in a clean refrigerator at a temperature of 40° F or below...Scrub firm produce, such as melons and cucumbers, with a clean produce brush...Refrigerate all produce that is purchased pre-cut or packaged.
   FDA, Selecting and Serving Produce Safely · checked 2026-10-08
10. wmj-r8-10 · case-control outbreak study
    Based on a case-control analysis, a number of food items consumed on 23 and 24 September 1996 were implicated in the outbreak, viz. a vegetable dish (P < 0.01), watermelon juice (P < 0.01) and cut watermelon (P < 0.001), papaya (P < 0.001) and pineapple (P < 0.05).
    Ann Acad Med Singap, 1997 · checked 2026-09-29
11. wmj-r8-08 · randomized crossover trial
    A single dose of l-citrulline or watermelon juice as a pre-exercise supplement appears to be ineffective in improving exercise performance
    J Sports Sci, 2015 · checked 2026-09-29
12. wmj-r8-09 · randomized crossover trial
    Short-term watermelon supplementation does not appear to enhance isometric force production, bench press performance, blood vessel diameter, or muscle oxygenation parameters compared to PL in resistance-trained men.
    Eur J Appl Physiol, 2022 · checked 2026-09-29
13. wmj-r8-12 · regulatory decision
    POL-HC-6231 Citrulline-malate Maintenance of adenosine triphosphate (ATP) levels through reduction of lactates in excess for recovery from muscle fatigue -/- Non-authorised
    EU Register on nutrition and health claims, claim POL-HC-6231, snapshot 2026-09-21 · checked 2026-09-29
14. wmj-r8-04 · randomized crossover trial
    Serum lycopene exhibited a significant treatment effect (p = 0.002) with a mean increase of 81%. However, this increase was not associated with changes in oxidative stress, inflammation, or cognitive function.
    J Nutr Gerontol Geriatr, 2021 · checked 2026-09-29
15. wmj-r8-07 · meta-analysis of RCTs
    The results indicate that l-citrulline supplementation and watermelon intake significantly reduced SBP (-4.02 mmHg [95 % CI: -6.54 to -1.50], P = 0.002) and DBP (-2.54 mmHg [95 % CI: -4.27 to -0.81], P = 0.004) in the elderly.
    Clin Nutr ESPEN, 2025 · checked 2026-09-29