Watermelon is about 91% water. Its red flesh gets its color from lycopene, the same pigment that colors tomatoes. On USDA data, raw watermelon has about 4,532 µg (micrograms) of lycopene per 100 g, against 2,573 µg in a raw red tomato.
A test of 50 red-fleshed cultivars found lycopene ranged from 33 to 100 mg per kilogram. So the amount depends on the variety.
Watermelon also gave its name to an amino acid. Japanese researchers first isolated citrulline from watermelon in 1914. The name comes from Citrullus, the Latin word for watermelon.
The body can turn citrulline into arginine, a building block for nitric oxide, a molecule that relaxes blood vessels. That is why researchers test the fruit for blood pressure and exercise.
Much of the research below does not test the fruit. Many trials used watermelon juice, a juice concentrate, an extract sold as a supplement, or plain L-citrulline, and each card says which.
The National Watermelon Promotion Board, a US industry group, funded several of the trials, and the cards say so. The muscle soreness trials are small, so treat their results with care.
Health benefits of watermelon
The top findings from 30 studies, strongest evidence first
What the stars mean
- Strong. Several randomized trials, pooled in a meta-analysis, point the same way, or regulators (FDA or EFSA) have approved the claim.
- Moderate. Good randomized trials support it, but there are fewer of them, or their results vary.
- Limited. Small, short or single trials, or mixed results. Promising, but it needs confirmation.
Population and lab studies get no stars: they show a link or a mechanism, not proof.
How we rate evidence →- ★★Lower top blood pressure number in supplement trialsIn 9 trials of watermelon supplementation (forms not stated), the top number (systolic pressure) fell. A review pooling citrulline supplements with watermelon found a drop of 4.02 mm Hg, though it does not isolate the fruit.
- ★★Lower cholesterol in watermelon supplement trialsIn 9 trials of watermelon supplementation (forms not stated), total and LDL cholesterol fell. The authors call the human evidence limited and ask for larger, longer trials.
- ★★Mixed results for artery stiffnessA review pooling citrulline supplement and watermelon trials reported better artery stiffness (pulse wave velocity) after weeks of watermelon, but one serving had no effect. A second review in middle-aged and older adults found no clear improvement.
- ★★Mixed effects on blood sugarFasting blood sugar rose in 9 trials of watermelon supplementation. Another review found blood sugar after watermelon was 0.6 mmol/L lower.
- ★More filling than low-fat cookiesIn 33 overweight or obese adults, two cups of watermelon a day for 4 weeks left them fuller than low-fat cookies with the same calories. Watermelon also lowered body weight and BMI.
All 30 studies, strongest evidence first
In 9 trials, watermelon lowered systolic pressure and cholesterol, raised blood sugar
This meta-analysis pooled 9 randomized trials (people put into groups by chance) of watermelon supplementation. Systolic blood pressure (the top number), total cholesterol and LDL (“bad”) cholesterol fell, but fasting blood sugar rose. Diastolic pressure, heart rate, BMI, body fat, insulin and CRP did not change clearly. The abstract does not say which forms of watermelon were pooled, and the authors call the human evidence limited and ask for larger, longer trials.
Weeks of watermelon improved artery stiffness by 0.9 m/s
This meta-analysis pooled 17 trials of L-citrulline supplements plus 5 longer-term and 5 single-meal trials of watermelon. The stiffness measure was pulse wave velocity, and a single serving had no effect. Supplements raised brachial artery dilation by 0.9 percentage points. Blood sugar after watermelon fell 0.6 mmol/L, and the authors say more research is needed on other heart and metabolic markers.
Citrulline plus watermelon lowered systolic pressure by 4.02 mm Hg
This meta-analysis of 15 randomized trials (415 middle-aged and older people) pooled citrulline supplements with watermelon intake, so it does not isolate the fruit. Diastolic pressure fell 2.54 mm Hg. Citrulline combined with L-arginine did better, with a 10.44 mm Hg drop in systolic pressure.
Watermelon did not clearly improve artery stiffness or dilation in older adults
This meta-analysis pooled 8 randomized trials in 176 middle-aged and older people. Citrulline supplements raised flow-mediated dilation, a test of artery function, by 1.81, but did not change pulse wave velocity. The authors say there are too few watermelon studies and call for larger ones.
Citrulline supplements cut muscle soreness at 24 hours, not at 72
This meta-analysis pooled 13 randomized trials (206 people) of citrulline supplements, most often 8 g of citrulline malate, not watermelon or juice. Soreness fell at 24 hours but not at 48 or 72 hours. Perceived exertion also fell, while blood lactate did not change.
Citrulline supplements did not improve aerobic exercise performance in 10 studies
In this meta-analysis, pooled results showed no benefit for performance (a standardized difference of 0.15), perceived exertion, oxygen use or lactate. The authors note that long-term protocols hinted at a benefit and need more studies. These were supplements, not watermelon.
Citrulline supplements did not change weight, BMI or body fat overall
This meta-analysis pooled 21 randomized trials of citrulline, the amino acid watermelon is known for, taken as a supplement. Fat mass fell in people over 40 and with doses above 6 g a day. Fat-free mass rose with 3 to 8 weeks of use, but the authors call these exploratory findings.
Two cups of watermelon daily left adults fuller than low-fat cookies
In this crossover trial, 33 overweight or obese adults ate the watermelon or low-fat cookies with the same calories for 4 weeks. Watermelon also lowered body weight, BMI, systolic blood pressure and waist-to-hip ratio, while cookies raised blood pressure and body fat. The National Watermelon Promotion Board funded the trial.
Watermelon for 4 weeks did not clearly change 24-hour blood pressure
This pilot trial assigned 39 adults with elevated blood pressure to no watermelon, 1 cup (152 g) or 2 cups (304 g) a day. Average 24-hour pressure was 130.2, 130 and 124.9 mm Hg, differences that could be chance. Blood L-arginine rose in the watermelon groups. The National Watermelon Promotion Board funded the trial.
Two glasses of watermelon juice daily did not change artery function
In this placebo-controlled crossover trial, 21 healthy postmenopausal women drank 360 mL of 100% watermelon juice twice a day for 4 weeks. Blood lycopene rose, but blood pressure, pulse wave velocity and flow-mediated dilation did not, and fasting glucose rose slightly. The authors say results may differ in younger adults and in people with high blood pressure.
Watermelon puree lowered a blood marker of artery inflammation by 6%
In this randomized trial, overweight postmenopausal women ate 100% watermelon puree daily for six weeks or had no intervention. The marker was sVCAM-1, and fasting glucose, insulin and insulin resistance did not differ between groups. Blood L-arginine rose 8%, cis-lycopene 32% and trans-lycopene 42%. The National Watermelon Promotion Board funded the study.
Daily blended watermelon lowered BMI and body fat in children
In this crossover trial, 17 children aged 10 to 17 with overweight or obesity finished 8 weeks on blended watermelon. Each had a daily cup of the whole fruit, flesh and rind, and also 8 weeks on a sugar-sweetened drink with the same calories. BMI percentile and HbA1c also fell, while inflammation, blood glucose, insulin and lipids did not change. The comparison was a sweet drink, not no drink.
After pregnancy sickness, women given watermelon held weight better over 2 weeks
This randomized trial followed 128 women discharged from hospital after hyperemesis gravidarum (severe pregnancy sickness). Of them, 64 got watermelon plus dietary advice and 64 advice alone. Weight change at week 2 was +0.25 kg with watermelon against -0.5 kg without. Symptom and appetite scores were better with watermelon, but rehospitalization and anti-nausea drug use did not differ.
Watermelon juice raised blood lycopene as much as tomato juice
In this 19-week crossover feeding study, 23 healthy adults ate a controlled diet. Plasma levels reached 1078 nmol/L with watermelon juice (20.1 mg of lycopene a day) and 960 with canned tomato juice (18.4 mg). On no juice they were 272. Doubling the watermelon dose to 40.2 mg did not raise them further.
Watermelon extract lowered arm systolic pressure by 15.1 mm Hg
In this placebo-controlled crossover trial, 14 obese adults with raised blood pressure took 6 g of extract a day for 6 weeks. The extract supplies L-citrulline and L-arginine; it is a supplement, not the fruit itself. Ankle systolic pressure fell 11.5 mm Hg and carotid wave reflection (augmentation index) 8.8%. It was very small.
Watermelon extract reduced artery stiffness by 1.2 m/s in obese women
In this randomized crossover trial, 12 obese postmenopausal women with high blood pressure took 6 g of extract a day for 6 weeks. The extract supplies L-citrulline and L-arginine, not the fruit. Compared with placebo, aortic systolic pressure fell 10 mm Hg and aortic diastolic pressure 7 mm Hg. The trial was small.
Watermelon extract lowered blood pressure, but no more than placebo
In this placebo-controlled trial, 40 people with raised blood pressure took 6 g of extract a day for 6 weeks, 20 per group. Systolic pressure fell from 137.8 to 126.0 mm Hg on the extract, but the difference from placebo could be chance. This was a supplement, not the fruit.
Watermelon juice before exercise went with less soreness 24 hours later
In this open-label trial, 42 non-athlete men did 8 weeks of endurance training. Before exercise they drank 710 mL of watermelon juice or a calorie-matched placebo drink, and they knew which. Soreness was lower at 24 hours, and chest and thigh muscles were thicker on ultrasound, but exercise performance did not differ.
A single 355 mL glass of juice did not reduce muscle soreness
This crossover trial gave 27 healthy adults watermelon juice, Gatorade, sugar water or water before submaximal exercise (below maximum effort). Heart rate recovery and blood lactate did not differ either. Juice prevented a post-exercise rise in blood pressure in women but not in men.
Watermelon juice reduced muscle soreness after 24 hours in 7 athletes
The 7 athletes drank natural juice, juice with added L-citrulline or a placebo before a maximum cycling test. The 500 mL of natural juice held 1.17 g of L-citrulline, and the enriched juice had 4.83 g of added L-citrulline. Both juices lowered recovery heart rate and soreness. A lab test on gut cells found citrulline was absorbed better from unheated juice.
Citrulline-enriched juice eased soreness 24 to 72 hours after a half marathon
In this randomized double-blind crossover trial, amateur male runners drank 500 mL of watermelon juice enriched to 3.45 g of L-citrulline, or a placebo drink. They drank it 2 hours before each of two half-marathons. Jump height was kept after the race with the juice and fell with placebo. This was a juice with added citrulline, not plain juice.
A week of juice concentrate did not improve bench press performance
In this crossover trial, 15 resistance-trained men took a watermelon concentrate with 2.2 g of L-citrulline a day, or placebo, for 7 days. Muscle oxygenation was 4.1% higher with watermelon, but force, bench press, vessel width and perceived effort did not differ. The National Watermelon Promotion Board funded the study.
Two weeks of concentrate: no endurance gain, higher systolic pressure
In this crossover trial, 8 active men took watermelon juice concentrate or an apple-juice placebo for 16 days. The dose was 300 mL a day, about 3.4 g of L-citrulline. Blood citrulline, arginine and nitrite rose, but resting systolic pressure was 130 mm Hg against 124 without supplement. Time to exhaustion was 550 seconds against 539 on placebo.
Watermelon 2 or 3 times weekly: 51% lower odds of sarcopenia
This snapshot (cross-sectional) study covered 3,733 adults in Tianjin, China (median age 65.8), of whom 12.6% had sarcopenia, the loss of muscle mass and strength. Both figures compare with people who never ate watermelon; once a week or less went with 28% lower odds. A snapshot study cannot show cause, and people with weaker muscles may simply eat less fruit.
More watermelon went with 26% lower colorectal cancer risk
This meta-analysis pooled 24 observational studies of fruit and colorectal cancer, with 1,068,158 people. Watermelon had 0.74 times the odds; apples (0.75) and kiwi (0.87) also had links, while most other fruits did not. The abstract does not say how many studies covered watermelon.
Watermelon powder lowered triglycerides, total cholesterol and LDL in rats
In this study in rats, not people, 32 young male rats ate 0.5% watermelon powder, L-arginine or a control diet for 9 weeks. The watermelon powder was given with an atherogenic (artery-clogging) diet. Both watermelon and L-arginine lowered CRP and oxidative stress. The National Watermelon Promotion Board funded the study.
In rats, 0.33% watermelon powder lowered blood fats, CRP and oxidative stress
This study was in rats, not people. Forty weanling male rats ate an atherogenic (artery-clogging) diet with or without watermelon powder. Some were also given a chemical, dextran sodium sulfate, used in the model. Watermelon-fed groups had lower triglycerides, total cholesterol, LDL and CRP.
Pomace juice lowered blood glucose and improved vessel relaxation in diabetic rats
In this study, Zucker diabetic fatty rats (6 per group) got 63% watermelon pomace juice in their drinking water for 4 weeks. Pomace is the pulp left after juicing. Arginine rose and fat accretion (fat build-up) fell. Lycopene (0.01%) or citrus pectin alone did not affect any measured parameter.
Watermelon juice reduced the toxicity of the cancer drug cisplatin in mice
This study was in mice with melanoma, not people. During cisplatin treatment, juice raised bone marrow cell numbers and lowered blood creatinine and urea. It did not shrink tumors on its own. It is not advice for people having chemotherapy.
Watermelon lycopene increased lung cancer cell death in a dish
This lab study treated human lung adenocarcinoma cells with 10 µM of lycopene from watermelon, gac fruit or tomato extracts, or synthetic lycopene. Tomato and gac extracts only made the cells multiply, and synthetic lycopene did nothing. The authors warn that antioxidant supplements may have no anticancer benefit and may even make cancer more aggressive.
Who should be careful with watermelon
Most people can eat watermelon freely. Take a little care if one of these applies:
- Irritable bowel syndrome. Monash University lists watermelon among fruits high in excess fructose. That is one of the FODMAPs, a group of fermentable carbohydrates that can trigger symptoms in some people. Our USDA data show about 3.4 g of fructose per 100 g, so a small slice may sit better than a large bowl.
- Pollen allergy. The American Academy of Allergy, Asthma and Immunology lists watermelon among foods that can cause an itchy mouth in people with grass pollen allergy. It lists melon for the same symptom in people with ragweed allergy. Among 1,000 people with ragweed allergy, 23% of those sensitive to more than three seasonal allergens reported melon or watermelon reactions. Only 1% of the rest did. Severe reactions are rare, but see a doctor if your throat swells or breathing gets hard.
- Diabetes. A normal portion has a low glycemic load (see the questions below), so this concern is small. A meta-analysis did find higher fasting blood sugar after watermelon, so it is worth checking your own readings.
How to choose, store and eat watermelon
- Fresh fruit: trials of the fruit used 1 to 2 cups (152 to 304 g) a day for 4 to 8 weeks, with mixed results. Two cups left overweight adults fuller than low-fat cookies, but 1 or 2 cups did not clearly change 24-hour blood pressure.
- Juice: trials used 355 to 710 mL, mostly around exercise, with mixed results on soreness. Two glasses a day for 4 weeks did not change artery function in postmenopausal women.
- Extract or citrulline: these are supplements, not the fruit. The blood pressure trials used 6 g of extract a day, and in the 40-person trial it did no better than placebo.
Pick a heavy melon with a hard rind and a yellow or creamy underside. Keep it whole at room temperature for up to about 2 weeks, and refrigerate wrapped cut pieces for 2 to 3 days. Scrub the rind with a clean produce brush before cutting, with no soap. Buy pre-cut melon only if it is refrigerated or on ice.
Residues are no reason to skip it: in USDA tests of 709 watermelon samples in 2022, 4 had a residue above the legal limit.
Sources
- FODMAP food list. Monash University FODMAP.
- Oral allergy syndrome (OAS). American Academy of Allergy, Asthma and Immunology.
- Asero R, Mistrello G, Amato S. The nature of melon allergy in ragweed-allergic subjects: a study of 1000 patients. Allergy Asthma Proc. 2011.
- Watermelon. glycemicindex.com, glycemic index and glycemic load database. Archived copy (the site was offline in October 2026).
- Robert SD, Ismail AA, Winn T, Wolever TM. Glycemic index of common Malaysian fruits. Asia Pac J Clin Nutr. 2008.
- Karimi E, Abaj F, Gholizadeh M, et al. Watermelon consumption decreases risk factors of cardiovascular diseases: a systematic review and meta-analysis of randomized controlled trials. Diabetes Res Clin Pract. 2023.
- Lum T, Connolly M, Marx A, et al. Effects of fresh watermelon consumption on the acute satiety response and cardiometabolic risk factors in overweight and obese adults. Nutrients. 2019.
- Singh K, Liao H, Edirisinghe I, Burton-Freeman B, Sandhu AK. Dose-response effect of watermelon consumption on ambulatory blood pressure in adults with elevated blood pressure: a randomized controlled pilot trial. Nutrients. 2025.
- Ellis AC, Mehta T, Nagabooshanam VA, et al. Daily 100% watermelon juice consumption and vascular function among postmenopausal women: a randomized controlled trial. Nutr Metab Cardiovasc Dis. 2021.
- Massa NM, Silva AS, Toscano LT, et al. Watermelon extract reduces blood pressure but does not change sympathovagal balance in prehypertensive and hypertensive subjects. Blood Press. 2016.
- Watermelon. University of Illinois Extension.
- Selecting and serving produce safely. US Food and Drug Administration.
- Pesticide Data Program annual summary, calendar year 2022. USDA Agricultural Marketing Service.
History of watermelon
Watermelon comes from northeastern Africa. Remains of watermelons, mostly seeds, about 5,000 years old have been found there. The plant scientist Harry Paris concluded that people domesticated the fruit in that region more than 4,000 years ago, first for water and food.
The closest relative alive today is the Kordofan melon, a Sudanese form with pale, non-bitter flesh. A 2021 genome study found that it carries the genetic signature of lost bitterness, but red flesh only became fixed in the domesticated watermelon. The same study found that fruit sweetness rose gradually over the course of domestication.
Egyptian tomb paintings, newly interpreted, suggest that watermelon was eaten as a dessert in the Nile Valley by 4,360 years ago. Another tomb image, of a large, striped, oblong fruit on a tray, dates to at least 4,000 years ago. Paris concluded that sweet dessert watermelons emerged in Mediterranean lands about 2,000 years ago.
From there the fruit traveled. Wikipedia, summarizing historical records, gives evidence of cultivation in India in the 7th century and in China by the 10th century. Cultivation followed in Córdoba, Spain, in 961 (introduced by the Moors) and in Seville in 1158.
Spanish settlers grew watermelons in Florida in 1576. The fruit was grown in Massachusetts in 1629, and in Peru, Brazil and Panama by 1650.
Seedless watermelons are a 20th century invention. Japanese scientists developed seedless triploid hybrids in 1939, though they lacked disease resistance. By 2014, seedless types made up nearly 85% of US watermelon sales. The heaviest watermelon on record, a Carolina Cross grown in Tennessee in 2013, weighed 159 kg (351 lb).
Today watermelon is a global crop. According to Wikipedia, world production in 2024 was 105 million tonnes, and China grew about 63.5 million tonnes of it, roughly 60% of the total.
Sources
- Paris HS. Origin and emergence of the sweet dessert watermelon, Citrullus lanatus. Ann Bot. 2015.
- Renner SS, Wu S, Pérez-Escobar OA, Silber MV, Fei Z, Chomicki G. A chromosome-level genome of a Kordofan melon illuminates the origin of domesticated watermelons. Proc Natl Acad Sci U S A. 2021.
- Watermelon. Wikipedia.
- Citrulline. Wikipedia.
- Koga Y, Ōtake R. Study report on the constituents of squeezed watermelon. Tokyo Kagaku Kaishi. 1914.
- Perkins-Veazie P, Collins JK, Davis AR, Roberts W. Carotenoid content of 50 watermelon cultivars. J Agric Food Chem. 2006.
- Watermelon, raw. USDA FoodData Central, FDC 167765.
- Tomatoes, red, ripe, raw, year round average. USDA FoodData Central, FDC 170457.
Frequently asked questions about watermelon
Is watermelon good for you?
For most people, yes: raw watermelon is about 91% water. Per 100 g it has 30 calories, 8.1 mg of vitamin C (9% of the FDA’s Daily Value) and 112 mg of potassium. The trial evidence is modest: a meta-analysis of 9 randomized trials found lower systolic blood pressure, total cholesterol and LDL, but higher fasting blood sugar. None of the 30 studies here reaches strong evidence.
How many calories are in watermelon?
Raw watermelon has 30 calories per 100 g, or 46 calories in a cup (152 g) of balls. A cup also has 0.9 g of protein and 0.6 g of fiber, and most of the calories come from carbohydrate. It is low in calories because it is so watery, with about 91.5 g of water per 100 g.
Does watermelon lower blood pressure?
Possibly, but the evidence is mixed and mostly not about the fruit. A meta-analysis of 9 trials found lower systolic pressure with watermelon. One pooling 15 trials of citrulline and watermelon found a 4.02 mm Hg drop in middle-aged and older adults. Against that, a 40-person trial of watermelon extract found no difference from placebo. In 39 adults, 1 or 2 cups of the fruit a day for 4 weeks did not clearly change 24-hour pressure. Do not swap blood pressure medicine for watermelon.
Does watermelon have more lycopene than tomatoes?
Gram for gram, yes, for raw fruit. Our USDA data show 4,532 µg of lycopene per 100 g of raw watermelon, against 2,573 µg per 100 g of raw red tomato. Lycopene in watermelon varies from 33 to 100 mg per kilogram across cultivars, though. In a 23-person feeding study, watermelon juice (20.1 mg of lycopene a day) and canned tomato juice (18.4 mg) gave similar blood lycopene.
Is watermelon high in sugar, and is it bad for blood sugar?
It has about 6.2 g of sugar per 100 g, and its glycemic index depends on which table you read. Older tables gave a high 76, the 2021 international tables list 50 (an average of four varieties), and a 10-person Malaysian study measured 55. A serving has little carbohydrate (about 9 g in 120 g). So the glycemic load is low either way: about 6 on the older value and 4.4 on the current one. A meta-analysis did find higher fasting blood sugar after watermelon, so people with diabetes should check their own readings.
Is watermelon good for weight loss?
It can help you feel full on few calories, but the evidence is small. In a trial funded by the National Watermelon Promotion Board, 2 cups a day for 4 weeks left 33 overweight adults fuller than low-fat cookies. Their body weight also fell, but a meta-analysis of 21 trials of citrulline supplements found no overall effect on weight or body fat. Raw watermelon has 30 calories per 100 g.
Does watermelon juice help muscle soreness?
Maybe a little, but the trials are small and mixed. A juice with added citrulline lowered soreness from 24 to 72 hours after a half marathon. In an open-label trial in 42 untrained men, 710 mL of juice lowered soreness at 24 hours, and 7 athletes had less soreness. But 355 mL in 27 healthy adults made no difference. A meta-analysis of citrulline supplements found less soreness at 24 hours but not at 72 hours.
How much watermelon can you eat a day?
No study sets an ideal amount. Trials of the fruit used 1 to 2 cups (152 to 304 g) a day for 4 to 8 weeks. Juice trials used 355 to 710 mL. One cup has 46 calories, but large portions bring more fructose, which can bother people with irritable bowel syndrome.