Watermelon, L-citrulline and heart health in people
What it found
Eating watermelon raises blood levels of L-citrulline and L-arginine, and in some small trials in people with risk factors for heart disease it lowered blood pressure and arterial stiffness.
In healthy adults, the same intake often made no difference to blood pressure or blood vessel function.
What they found
Studies in people
Blood pressure in adults
In pre-hypertensive adults, 6 weeks of watermelon providing 2.7 g of L-citrulline and 1.3 g of L-arginine lowered central and peripheral blood pressure and arterial stiffness. A concentrated watermelon powder providing 4 g of L-citrulline and 2 g of L-arginine also lowered several blood pressure measures in obese, pre-hypertensive adults.
No effect in healthy adults
Healthy adults who drank 500 mL of watermelon juice daily for 2 weeks, or 360 mL daily for 4 weeks, saw no rise in blood L-citrulline or L-arginine and no change in blood pressure, blood vessel function or arterial stiffness.
Single doses and blood flow
A single dose of wild watermelon juice raised nitric oxide production and blood flow in the lower leg arteries of healthy women. A single dose of microencapsulated watermelon rind also helped after a period of restricted blood flow in healthy people.
Rind and seeds in overweight adults
Overweight or obese adults who ate watermelon rind, flesh or seeds saw their blood L-citrulline and L-arginine rise, but there was no improvement in the brachial artery's ability to widen. Only six people took part.
Other findings
L-citrulline in watermelon
Red watermelon rind holds 60.0 to 500 mg of L-citrulline per 100 g fresh weight, more than the pulp, which holds 40.0 to 160 mg per 100 g. Seeds had none detected.
How much fruit is needed
To reach the minimum effective dose of 2 to 3 g of L-citrulline a day, a person would need to eat less than 1 to 3 kg of fresh red rind or 2.5 to 5 kg of fresh red pulp daily.
What the authors conclude
“The beneficial effects of oral L-citrulline ingestion through watermelon require additional evidence, but it has already been demonstrated that it does not undergo hepatic metabolism, instead being transported to the kidneys to participate in de novo L-arginine synthesis.”
Also in their conclusions
- They say that oral L-citrulline from watermelon needs more evidence before it can be recommended for people with heart disease risk factors.
- They note that it has shown potential to improve blood flow, lower blood pressure and reduce arterial stiffness in adults who already have these risk factors.
- They call for longer randomised trials, dose-response studies, and tests in specific groups such as older sedentary adults and people with several heart disease risk factors.
How it was done
The authors say that when blood vessels work poorly, the body makes less nitric oxide, and this is linked to high blood pressure, stiff arteries and heart disease. They wanted to see whether the L-citrulline in watermelon can raise L-arginine and nitric oxide, and so help blood vessels.
They gathered and discussed published studies on watermelon's nutrients and on L-citrulline, including small trials where adults ate or drank watermelon in various forms. The trials lasted from a single dose up to 6 weeks, and included healthy adults, pre-hypertensive and obese adults, and postmenopausal women.
What it can’t tell you
- Most of the trials were short, lasting from a single dose up to 6 weeks, so they cannot show what happens over months or years.
- The trials used different forms of watermelon and different doses, which makes it hard to compare results or generalise them.
- Some trials were very small, and in healthy people the results were mixed, so it is not clear who would benefit most.
Who paid
- Funding
- Funded by Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro - Brasil (FAPERJ) (from the PubMed record).
- Conflicts
- The authors declare no conflicts of interest.
- Authors work at
- Federal University of Rio de Janeiro (UFRJ), Brazil
The paper
- Title
- Watermelon Nutritional Composition with a Focus on L-Citrulline and Its Cardioprotective Health Effects-A Narrative Review
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Studies in people
- Summarised from
- Full text
- Licence
- CC BY. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- Baião DDS, da Silva DVT, Paschoalin VMF (2025). Watermelon Nutritional Composition with a Focus on L-Citrulline and Its Cardioprotective Health Effects-A Narrative Review. Nutrients. doi:10.3390/nu17203221Free full textPubMed 41156475DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error