Watermelon: Nutrients, What Research Shows and Safety
What the evidence says about watermelon as a food: nutrients, lycopene and citrulline, blood pressure and exercise studies, allergy and food-safety notes.
Content last updated . This page has not been medically reviewed.
Watermelon (Citrullus lanatus) is the fruit of a trailing vine in the gourd family (Cucurbitaceae). The red, juicy flesh is the part most people eat. People eat it for its water, its vitamin C and its red pigment lycopene. This page keeps the food apart from supplements and from hype, and says what research does and does not show.
Read this first
- Allergy is possible with any food. For trouble breathing or swelling of the face or throat, call 911. See food allergy basics and emergency signs.
- Cut melon needs careful handling: scrub the rind before cutting and keep cut pieces cold. [8]
- Most blood pressure research used citrulline supplements or watermelon products, not slices of fresh fruit. [2][3]
- Honest summary: watermelon is a low-calorie, mostly-water fruit with some vitamin C and lycopene. Studies of its effects on health are small and mixed, and none shows that it prevents or treats a disease.
What is in it (USDA values)
| Nutrient | Per 100 g | Per 1 cup, diced (152 g) | % Daily Value per serving |
|---|---|---|---|
| Energy | 30 kcal | 46 kcal | - |
| Water | 91.5 g | 139 g | - |
| Total sugars | 6.2 g | 9.4 g | - |
| Fiber | 0.4 g | 0.6 g | 2% |
| Vitamin C | 8.1 mg | 12.3 mg | 14% |
| Vitamin A (RAE) | 28 mcg | 43 mcg | 5% |
| Potassium | 112 mg | 170 mg | 4% |
| Magnesium | 10 mg | 15 mg | 4% |
| Copper | 0.04 mg | 0.06 mg | 7% |
| Folate (DFE) | 3 mcg | 5 mcg | 1% |
| Vitamin K | 0.1 mcg | 0.2 mcg | 0% |
| Lycopene | 4,532 mcg | 6,889 mcg | no Daily Value set |
Source: USDA FoodData Central, Watermelon, raw (SR Legacy). [1] % Daily Value uses the FDA 2016 Daily Values; values vary with variety, ripeness and storage.
Watermelon's red color comes mainly from lycopene, a carotenoid. The Linus Pauling Institute lists about 6.9 mg per cup, and says tomatoes and tomato products supply most lycopene in the US diet. [7] USDA also lists a little beta-carotene. [1] Evidence about lycopene and health comes mostly from observational studies and supplement trials in people, and it is mixed (see below). Watermelon also contains citrulline, an amino acid that is the subject of the blood pressure studies. [11]
What research says
| Health goal | What the sources found | Strength of evidence | What was studied |
|---|---|---|---|
| Blood pressure | A 2025 meta-analysis of 15 trials (415 people) of L-citrulline or watermelon found average drops of about 4.0 mmHg (systolic) and 2.5 mmHg (diastolic). [2] A 2026 review in postmenopausal women (12 trials) saw drops in some trials, up to 9 mmHg systolic. [3] | Promising but limited | Middle-aged and older adults; mostly citrulline supplements and watermelon products |
| Blood vessel function | Reviews report better flow-mediated dilation in some trials, with large differences between studies. [3][4] | Mixed | Citrulline, rind juice and watermelon products |
| Muscle soreness after exercise | A 2026 review of 36 trials of plant foods reported less soreness 24 to 72 hours after exercise in several, but inconsistent effects on performance. [5] In one 8-week trial of 42 men, watermelon juice (710 mL before exercise) was linked to lower soreness at 24 hours. [6] | Mixed | Juice, active adults and non-athletes |
| Heart attacks, strokes, deaths | The sources we read found no evidence on these outcomes. [4] | Insufficient evidence | - |
| Prostate cancer and heart disease (lycopene) | Observational results are inconsistent and lycopene supplement trials have shown no clear benefit; it is unclear whether lycopene or other food factors explain associations. [7] | Mixed | Lycopene-rich diets and lycopene supplements, not watermelon specifically |
| Hydration | Watermelon is about 91% water. [1] We found no trial of its effect on hydration status. | Insufficient evidence | - |
Eaten as food vs taken as a supplement or extract. Eating watermelon adds water, vitamin C and lycopene to a meal. The blood pressure research mostly used L-citrulline powder or processed watermelon products, and one reviewed approach used a microencapsulated rind juice. [2][11] Those results should not be read as proof that fresh fruit does the same. A benefit seen with a supplement is not a promise for the food.
How much is a normal serving
The USDA household portions in our data are 1 cup diced (152 g), 1 cup balls (154 g), 10 watermelon balls (122 g) and 1 wedge, about 1/16 of a melon (286 g). [1] These are information, not a prescription. We could not read the MyPlate or Dietary Guidelines pages for an official daily fruit figure, so we do not quote one here; see fruit juice vs whole fruit for juice versus fruit. Fresh melon is the form USDA measured here; we did not find sourced nutrient data for frozen or dried watermelon, or on how cooking or storage changes the nutrients.Safety, allergy and medicines
- Allergy to the seed. A 2026 case series in children reported that some who were allergic to pumpkin seed were also sensitised to watermelon seed, and some reacted after eating it, in some cases with anaphylaxis. [9] That paper is about seeds, not the flesh.
- Pollen-food allergy. Pollen-food allergy syndrome is a cross-reaction between pollen and some plant foods; symptoms are usually in the mouth and throat and anaphylaxis is rare. [10] The sources we read do not tell us how often watermelon is involved.
- Emergency. For trouble breathing or swelling of the face or throat, call 911. See when to seek medical help after a food reaction.
- Sugar. USDA lists 6.2 g of sugars per 100 g (9.4 g per cup diced). [1] People who count carbohydrates for diabetes can use these figures; we did not read a sourced statement on its effect on blood sugar.
- Potassium and kidney disease. Watermelon has a modest amount of potassium (about 4% of the Daily Value per cup). [1] We could not read an official source on potassium limits, so we make no claim. People told to limit potassium, or who take medicines that raise potassium, should ask their care team. See foods, kidney disease, potassium and oxalates.
- Medicines. The sources we read did not describe interactions with watermelon as a food. A pharmacist can check; see foods and medicine interactions.
- Citrulline supplements. Trials of citrulline in postmenopausal women reported no adverse effects. [3] Anyone on blood pressure medicine should ask a clinician before using a supplement.
- Pregnancy. We did not find a watermelon-specific statement in the sources we read. See foods in pregnancy.
- Pesticide residues. Proper evidence not found in the sources we read.
Choosing, storing and food safety
- Scrub melons with a clean produce brush under running water before cutting, so rind bacteria are not carried into the flesh. Do not use soap or produce wash. [8]
- Refrigerate cut melon at 40 F (4 C) or below. [8]
- When buying pre-cut melon, choose pieces that are refrigerated or kept on ice, and discard produce that looks rotten. [8]
- Cut away bruised or damaged areas. [8] See also fresh, frozen and canned produce.
Related pages
Health connections for Watermelon
What research links to eating or drinking this food, and how strong the evidence is. Many studies are observational or use juice, powder, oil or extracts rather than the food as eaten; each card says which.
Water content and fluid intake
Established roleWatermelon is about 91% water by weight (USDA), so it adds to daily fluid intake. We did not find a trial showing it hydrates better than other fluids.
Supplements: Not applicable; this is a normal food property.
Vitamin C from the whole fruit
Established roleOne cup of diced watermelon (152 g) gives about 12 mg of vitamin C, roughly 14% of the FDA Daily Value (USDA).
Supplements: Eating the fruit contributes to intake; no evidence is claimed here of benefit above adequate intake.
Citrulline and blood pressure
Preliminary or mixedA 2025 meta-analysis of 15 trials (415 people, middle-aged and older adults) of L-citrulline or watermelon found small average falls in blood pressure (systolic -4.0, diastolic -2.5 mmHg). Most of that evidence is for citrulline supplements, not for eating watermelon slices.
Supplements: Results come from citrulline supplements and watermelon products mixed together; the review does not show that eating the fresh fruit lowers blood pressure.
Blood vessel function (surrogate measures)
Preliminary or mixedReviews report better flow-mediated dilation and blood pressure in some trials of citrulline or watermelon products, with large differences between studies. No evidence of fewer heart attacks, strokes or deaths.
Supplements: Mostly supplements, rind juice or watermelon products; fresh fruit was not clearly tested.
Muscle soreness after exercise
Preliminary or mixedA 2026 review of 36 trials of plant foods, including watermelon, found some reports of less soreness 24-72 hours after exercise but inconsistent results for performance. In one 8-week trial of 42 men, 710 mL of watermelon juice before exercise was linked to lower soreness at 24 hours.
Supplements: Studies used juice in small groups; the findings do not apply automatically to eating slices of fruit.
Lycopene, heart disease and prostate cancer
Preliminary or mixedWatermelon is a source of lycopene (about 6.9 mg per cup, Linus Pauling Institute). Observational studies of lycopene-rich diets are mixed, and supplement trials have not shown clear benefit; it is unclear whether lycopene itself or other food factors explain the associations.
Supplements: Lycopene supplement trials found no effect on blood pressure or cholesterol in a pooled analysis; evidence is limited and mixed.
Heart attacks, strokes and deaths
Not enough evidenceThe sources we read found no evidence that watermelon or citrulline lowers heart attacks, strokes or deaths. Outcome trials have not been done.
Supplements: No good evidence of benefit on disease outcomes.
Potassium and kidney disease: not verified
Not enough evidenceWatermelon has a modest amount of potassium (about 4% of the Daily Value per cup, USDA). We could not read an official source on potassium limits in kidney disease, so we make no claim; people on potassium-limiting advice should ask their care team.
Supplements: Unknown from the sources read.
Connected topics
Open a group to see how each topic connects and how strong the evidence is.
Health goals (2)
- Blood Pressure SupportPreliminary or mixed
Small average blood pressure falls were seen in trials of citrulline or watermelon products in middle-aged and older adults; most evidence is for supplements, not fresh fruit.
- Muscle RecoveryPreliminary or mixed
Some trials of watermelon juice or citrulline-rich foods reported less soreness 24-72 hours after exercise; results were inconsistent.
Body systems (3)
- Cardiovascular SystemPreliminary or mixed
Small average blood pressure falls were seen in trials of citrulline or watermelon products in middle-aged and older adults; most evidence is for supplements, not fresh fruit.
- Heart & CirculationPreliminary or mixed
Small average blood pressure falls were seen in trials of citrulline or watermelon products in middle-aged and older adults; most evidence is for supplements, not fresh fruit.
- Immune SystemDocumented risk
Allergic reactions to watermelon seed and pollen-food allergy are documented; see the safety section.
Body parts (1)
- Blood VesselsPreliminary or mixed
Citrulline-based products improved flow-mediated dilation in some trials; findings are mixed.
Functional actions (2)
- Cardiovascular SupportPreliminary or mixed
Small average blood pressure falls were seen in trials of citrulline or watermelon products in middle-aged and older adults; most evidence is for supplements, not fresh fruit.
- Muscle RecoveryPreliminary or mixed
Less soreness reported in some juice trials; performance results inconsistent.
Conditions & symptoms (3)
- Essential HypertensionPreliminary or mixed
Small average blood pressure falls in trials of L-citrulline or watermelon products; this does not show that eating watermelon treats high blood pressure.
- Food AllergyDocumented risk
Watermelon seed allergy, sometimes with anaphylaxis, was reported in children who were sensitised to pumpkin seed.
- Food PoisoningDocumented risk
FDA gives specific handling advice for melons (scrub the rind, refrigerate cut pieces).
Documented risks and interactions (2)
- Allergy to watermelon seed, and pollen-food allergy. A 2026 case series reported that some children sensitised to pumpkin seed also reacted to watermelon seed, in some cases with anaphylaxis. Pollen-food allergy syndrome usually causes mouth and throat symptoms and rarely anaphylaxis. For trouble breathing or swelling of the face or throat, call 911.
- Food safety of cut melon. FDA advises scrubbing melons before cutting, refrigerating cut melon at 40 F or below, and buying only pre-cut pieces that are chilled or on ice.
Frequently asked questions
Does watermelon lower blood pressure?
Trials of L-citrulline or watermelon products found small average drops, but most used supplements or processed products rather than fresh fruit. [2][3] Eating watermelon is not a treatment for high blood pressure.
Is watermelon a good source of lycopene?
Yes. The Linus Pauling Institute lists about 6.9 mg per cup, though tomatoes supply most lycopene in the US diet. [7] Whether lycopene itself improves health is not settled. [7]
Can watermelon help sore muscles after exercise?
Some trials, mostly of juice, reported less soreness one to three days after exercise, but results were inconsistent. [5][6]
Is watermelon high in sugar?
USDA lists 6.2 g of sugars per 100 g, or about 9.4 g in a cup of diced fruit. [1]
How do I cut watermelon safely?
Scrub the rind under running water first, then keep cut pieces refrigerated at 40 F or below. [8]
References
- U.S. Department of Agriculture. FoodData Central: Watermelon, raw (SR Legacy, FDC 167765). April 2018 release. Read 2026-10-23.
- Luo P et al. L-citrulline supplementation and watermelon intake and blood pressure in middle-aged and older adults: systematic review and meta-analysis of RCTs. Clin Nutr ESPEN 2025. PMID 40789388. Abstract read 2026-10-23.
- Bahari H et al. Citrulline supplementation in postmenopausal women: a systematic review of vascular, muscular, and metabolic effects. BMC Women's Health 2026. PMID 41588439. Abstract read 2026-10-23.
- Katsanaki E et al. Effects of Nutritional Supplements on Vascular Function: A Narrative Review. J Clin Med 2026. PMID 42513607. Abstract read 2026-10-23.
- Nguyen DHN et al. Plant-derived whole foods and food-based supplements on post-exercise recovery: a systematic review of human intervention trials. Nutrients 2026. PMID 42797032. Abstract read 2026-10-23.
- Norouzzadeh M et al. Watermelon juice, muscle hypertrophy, exercise performance and muscle soreness in non-athlete men: a randomized controlled trial. Food Sci Nutr 2025. PMID 41089757. Abstract read 2026-10-23.
- Linus Pauling Institute, Oregon State University. Carotenoids. Last updated 2023. Read 2026-10-23.
- US Food and Drug Administration. Selecting and Serving Produce Safely. Read 2026-10-23.
- Acikalin B et al. IgE-mediated pumpkin seed allergy in children: case series and narrative review. Allergy Asthma Proc 2026. PMID 42343505. Abstract read 2026-10-23.
- Marzec A et al. Pollen-Food Allergy Syndrome in Children: Global Prevalence and Pathogenesis. Nutrients 2026. PMID 42514315. Abstract read 2026-10-23.
- Alvares TS. Valorization of Beetroot and Watermelon by-Products as Functional Ingredients Targeting Nitric Oxide Pathways. Curr Nutr Rep 2026. PMID 42891784. Abstract read 2026-10-23.