Watermelon Seed
Quick Facts
- What it is: The seed of the watermelon, used as a food and, in American folk tradition, as a tea for urinary and blood pressure complaints.
- Main uses: Urinary and bladder complaints, Fluid retention, High blood pressure (unproven), Nourishing food
- Active ingredients: Citrulline, Arginine, Cucurbocitrin, Magnesium, Potassium, Linoleic acid
- Forms: Roasted seeds, Hulled kernels, Crushed seed tea, Seed butter, Seed oil, Protein powder
- Time to effect: Unknown; it may do nothing at all.
- Side effects: Mild digestive upset at most; choking risk for small children and rare melon allergy.
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What is Watermelon Seed?
Watermelon seed is the seed of the watermelon, Citrullus vulgaris (also written Citrullus lanatus). It is an everyday food. People eat the seeds roasted, grind them into a paste, or steep crushed seeds in hot water as a tea.
In American folk and Eclectic practice the seed, not the sweet flesh, was the part used. Healers steeped it for urinary and kidney complaints. The same tea was later talked up for high blood pressure.
Here is the honest verdict on the evidence. We found no controlled human trials of watermelon seed for any of these uses. Traditional use is not proof that a remedy works, and it is not proof that it is safe.
As a plain food, roasted seeds are eaten widely with no sign of harm. That is a different claim from saying seed tea treats anything. This page keeps those two things apart.
How does Watermelon Seed work?
Nobody has shown how watermelon seed works in people, because the human studies have not been done. What follows is proposed, not proven.
Folk writers said the tea acts as a diuretic (something that makes you pass more urine). That effect has not been measured in a modern human trial.
Old reports from the 1930s and 1940s named a seed compound called cucurbocitrin. In animal work it was said to widen blood vessels and lower blood pressure. That work was small, and it has not been repeated.
The seed also holds citrulline, a building block of protein. In trials of pure citrulline supplements, large doses can help the body make more nitric oxide (a gas that relaxes blood vessels). A cup of seed tea holds far less, and the tea itself has never been tested this way.
The minerals in the seed, such as magnesium and potassium, are real and useful as food. They do not make the tea a medicine.
What forms does Watermelon Seed come in?
You will meet watermelon seed in these forms.
- Whole roasted seeds, salted or plain, eaten as a snack. - Hulled kernels, sold loose or in trail mixes. - Crushed seed tea, made by steeping the seed in hot water.
- Tea bags and loose blends sold as kidney or bladder teas. - Seed butter, a spread like tahini. - Cold-pressed seed oil, used in cooking and on skin.
- Seed protein powder, used in plant-based blends. - Egusi-style ground melon seed, used to thicken West African soups.
Food forms are the best studied, in the sense that people have eaten them for a long time. Tea and extract products are not standardised. Two brands can differ a lot.
Where it comes from:
Watermelon seed had a modest but steady place in nineteenth and early twentieth century American folk and Eclectic medicine. Eclectic physicians were a group of American doctors who leaned on plant remedies.
Their texts listed seed tea for irritated bladders, scanty urine, and what they called gravel, meaning grit or small stones in the urinary tract. The flesh was treated as food, and the seed as the active part.
From the 1930s, a few researchers took an interest in a seed compound and blood pressure. Popular health writing picked this up and kept repeating it for decades.
In West Africa and parts of Asia, melon seeds have a long food history, in soups, pastes and snacks. That use is culinary and nourishing rather than medicinal. None of this history tells you what the tea does in your body.
Who should avoid Watermelon Seed?
- Do not give whole seeds to children under four years old, because of the choking risk.
- Do not stop or replace a prescribed blood pressure medicine with watermelon seed tea.
- Do not use seed tea or seed supplements if you have chronic kidney disease, unless your kidney doctor agrees.
- Do not use seed tea regularly if you take lithium, without asking the doctor who manages it.
- Do not use it if you have ever had an allergic reaction to watermelon, melon or cucumber.
- Avoid strong seed teas, extracts and seed supplements while pregnant or breastfeeding, as they have not been tested. Eating the seeds as food is not a concern.
- Avoid it if you follow a daily fluid limit for heart failure or dialysis, unless your care team approves.
- Do not use it to self-treat a suspected urine infection or kidney stone.
When should you see a doctor?
Stop and see a doctor if any of these happen:
- Your lips, tongue or throat swell, or you find it hard to breathe. Call emergency services. - You feel faint, very dizzy or weak after drinking the tea. - You have burning when you pass urine, fever, or pain in your back or side. - You see blood in your urine. - You have severe one-sided back pain with vomiting, which can mean a kidney stone. - Your swelling gets worse, or new breathlessness starts. - Your blood pressure readings drop low, or swing about.
Also tell your doctor if you plan to drink seed tea daily and you take any regular medicine.
Is Watermelon Seed legal where you live?
In the United States, the United Kingdom and the European Union, watermelon seed is an ordinary food. Teas, oils and powders are sold as foods or food supplements, not as approved medicines. No regulator has approved it to treat blood pressure, kidney or urinary disease.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
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