NutriDex

The Supplement Research Compendium
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Watermelon

Citrullus lanatus

Hydrating summer fruit rich in citrulline and lycopene

Moderate evidence 🍎Fruits

✚ Updated · How we grade evidence

Evidence tier
Moderate
Research weight
Citations
8 verified / 8
Classification
Fruits
❝
What the evidence says. Several controlled trials; effects real but modest or context-dependent.

Nutrition per serving 1 wedge (286 g)

286gSERVING
  • Water 261.5 g92%
  • Sugars 17.7 g6%
  • Fibre 1.1 g0%
  • Other carbs 2.8 g1%
  • Protein 1.7 g1%
  • Fat 0.4 g0%
What's in one serving, by weight — average composition (USDA).
Vitamin C26%Vitamin A (RAE)9%Potassium7%Magnesium7%Fiber4%
One serving as % of the adult daily requirement (FDA Daily Values). The bold outer ring = 100% of a day's needs.
86 kcal1.7 g protein1.1 g fiber0.4 g fat
NutrientPer serving% daily value
Vitamin C23 mg26%
Vitamin A (RAE)80 mcg9%
Potassium320 mg7%
Magnesium29 mg7%
Fiber1.1 g4%
Lycopene13 mg0%
Sugars18 g35%

Composition data: USDA FoodData Central ↗

What is Watermelon?

Watermelon (Citrullus lanatus) is a fruit used for modestly lowers blood pressure (citrulline/arginine pathway). NutriDex grades the human evidence as Moderate. Watermelon is best known among fruits for its L-citrulline content, which the body converts to L-arginine to support nitric-oxide-mediated vasodilation. A 2023 meta-analysis of 9 randomized trials found watermelon consumption significantly lowered systolic blood pressure and improved total cholesterol and LDL, though it unexpectedly raised fasting blood glucose. A 2025 meta-analysis of L-citrulline/watermelon trials in middle-aged and older adults confirmed modest reductions in systolic (~-4 mmHg) and diastolic (~-2.5 mmHg) blood pressure. Small RCTs of watermelon extract also show reduced arterial stiffness and aortic blood pressure in obese hypertensive adults, and watermelon juice may modestly aid post-exercise recovery, though evidence here is mixed. Most trials are small, short, and often use concentrated extracts or juice rather than typical whole-fruit servings. The fruit is largely water with a high glycemic index but low glycemic load per realistic portion. Overall the cardiovascular signal is consistent but modest, warranting a conservative "moderate" rating.

Purported Benefits

✓Modestly lowers blood pressure (citrulline/arginine pathway)
✓Supports nitric-oxide-mediated vasodilation
✓May reduce arterial stiffness in adults with prehypertension/hypertension
✓High water content supports hydration
✓Provides lycopene, an antioxidant carotenoid
✓May improve some cardiometabolic lipid markers (total cholesterol, LDL)

Dosing & Compounds

Typical Dose
A typical serving is one wedge (~286 g) or 1-2 cups of diced flesh; cardiovascular trials often use larger amounts (~2-3 cups daily or watermelon extract supplying ~1-6 g citrulline/arginine).
Active Compounds
L-Citrulline (non-protein amino acid)L-ArginineLycopene (carotenoid)Beta-carotene (provitamin A)Vitamin C (ascorbic acid)PotassiumMagnesiumCucurbitacin E

Safety & Cautions

Generally very safe as a food. The high glycemic index means large portions can spike blood glucose, relevant for people with diabetes (though glycemic load per serving is low). It is a high-FODMAP food (fructose, mannitol) and may cause bloating, gas, or diarrhea in sensitive individuals or those with IBS. Rare allergy can occur, sometimes via oral allergy syndrome cross-reacting with ragweed pollen. Concentrated citrulline/arginine supplements may add to the blood-pressure-lowering effect of antihypertensive drugs and PDE5 inhibitors; no notable CYP3A4/grapefruit-type interaction. Educational only — always check with your doctor or pharmacist before combining Watermelon with any medicine.

Key Studies

Meta-analysis Karimi 2023 ✓ PubMed
Meta-analysis of 9 RCTs: watermelon consumption significantly lowered systolic blood pressure, total cholesterol and LDL, though fasting blood glucose rose.
Meta-analysis Luo 2025 ✓ Full text
Meta-analysis (15 RCTs, 24 datasets, n=415): L-citrulline supplementation/watermelon intake significantly reduced SBP (-4.02 mmHg) and DBP (-2.54 mmHg) in middle-aged and older adults.
Meta-analysis Frontiers in Nutrition 2025 ✓ Full text
Systematic review and meta-analysis of RCTs found L-citrulline supplementation and watermelon intake improved arterial stiffness and endothelial function in middle-aged and older adults.
Meta-analysis Smeets, Mensink & Joris 2022 (Br J Nutr) ✓ Source
Meta-analysis of RCTs found longer-term L-citrulline supplementation and watermelon consumption may improve vascular function; postprandial glucose fell by 0.6 mmol/L but no other postprandial cardiometabolic effects were seen.
RCT Singh et al. 2025 (Nutrients) ✓ Full text
Randomized placebo-controlled pilot trial in 39 adults with elevated BP found daily watermelon (152 or 304 g/day) for 4 weeks; assessed effects on 24-hour ambulatory blood pressure as a dietary source of L-citrulline/L-arginine.
RCT Figueroa 2014 ✓ PubMed
RCT (n=13 obese hypertensive adults): 6-week watermelon supplementation reduced aortic blood pressure and myocardial oxygen demand during the cold pressor test.
RCT Figueroa 2012 ✓ PubMed
RCT (n=14 obese pre/hypertensive adults): 6-week watermelon extract (6 g citrulline/arginine) reduced ankle and brachial blood pressure and carotid augmentation index (arterial stiffness).
RCT Tarazona-Díaz 2013 ✓ PubMed
Crossover trial in athletes: 500 mL watermelon juice (1.17 g citrulline) helped reduce 24-h muscle soreness and recovery heart rate; natural juice citrulline more bioavailable.
8 sources cited · 8 verified Search all studies on PubMed ↗

Common questions about Watermelon

What is Watermelon used for?

Watermelon is most often taken for Modestly lowers blood pressure (citrulline/arginine pathway), Supports nitric-oxide-mediated vasodilation, May reduce arterial stiffness in adults with prehypertension/hypertension, High water content supports hydration. Hydrating summer fruit rich in citrulline and lycopene

Does Watermelon work — what does the evidence say?

Moderate evidence. Several controlled trials; effects real but modest or context-dependent. Watermelon is best known among fruits for its L-citrulline content, which the body converts to L-arginine to support nitric-oxide-mediated vasodilation. A 2023 meta-analysis of 9 randomized trials found watermelon consumption significantly lowered systolic blood pressure and improved total cholesterol and LDL, though it unexpectedly raised fasting blood glucose. A 2025 meta-analysis of L-citrulline/watermelon trials in middle-aged and older adults confirmed modest reductions in systolic (~-4 mmHg) and diastolic (~-2.5 mmHg) blood pressure. Small RCTs of watermelon extract also show reduced arterial stiffness and aortic blood pressure in obese hypertensive adults, and watermelon juice may modestly aid post-exercise recovery, though evidence here is mixed. Most trials are small, short, and often use concentrated extracts or juice rather than typical whole-fruit servings. The fruit is largely water with a high glycemic index but low glycemic load per realistic portion. Overall the cardiovascular signal is consistent but modest, warranting a conservative "moderate" rating.

What is the typical dose of Watermelon?

A typical serving is one wedge (~286 g) or 1-2 cups of diced flesh; cardiovascular trials often use larger amounts (~2-3 cups daily or watermelon extract supplying ~1-6 g citrulline/arginine).

Is Watermelon safe? Any cautions or side effects?

Generally very safe as a food. The high glycemic index means large portions can spike blood glucose, relevant for people with diabetes (though glycemic load per serving is low). It is a high-FODMAP food (fructose, mannitol) and may cause bloating, gas, or diarrhea in sensitive individuals or those with IBS. Rare allergy can occur, sometimes via oral allergy syndrome cross-reacting with ragweed pollen. Concentrated citrulline/arginine supplements may add to the blood-pressure-lowering effect of antihypertensive drugs and PDE5 inhibitors; no notable CYP3A4/grapefruit-type interaction.

How many studies support Watermelon?

NutriDex cites 8 sources for Watermelon, graded "Moderate".

Cite this page
APA

Peh, D. (2026). Watermelon (Citrullus lanatus): Benefits, Dosage, Side Effects & Evidence. NutriDex — The Supplement Research Compendium. Retrieved 26 Jun 2026, from https://nutridex.info/s/watermelon

BibTeX
@misc{nutridex_watermelon,
  author       = {Peh, Daryl},
  title        = {Watermelon (Citrullus lanatus): Benefits, Dosage, Side Effects \& Evidence},
  year         = {2026},
  howpublished = {NutriDex --- The Supplement Research Compendium},
  url          = {https://nutridex.info/s/watermelon},
  note         = {Reviewed by Dr Daryl Peh, MBBS Singapore, MMed FM. Accessed 2026-06-26}
}

For medical claims, citing the underlying primary studies linked above is preferred. NutriDex is an educational reference, not medical advice.

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