Watermelon was a fruit that the Prophet ﷺ used often. It has a very important place since it prevents dehydration, especially during the fasting period of Ramadan. It is reported in the authentic collections of al-Bukhari and Muslim that the Prophet ﷺ would eat watermelon with fresh dates and would say: "We repel the heat of this one with the coolness of that one," and repelling one thing with its opposite is a principle of medicine.
Indeed, dates are hot and watermelon is cold and moist. Ibn al-Qayyim says that watermelon cleanses, meaning that it is a diuretic; it is also a laxative, so it is very effective for digestion. It is also useful for energy metabolism since it is rich in vitamins C and B6, and it is useful against dizziness. It also contains sodium and potassium.
In Prophetic Medicine, the fruit is used, but also the seeds, which can be found in capsule form; indeed, these contain citrulline, which is an amino acid that stimulates the heart, useful for diabetes, and for erection problems in men.
The hadith, and the rule of opposites
Aisha reported that the Prophet ﷺ ate watermelon (bittikh) with fresh dates (rutab), and said: "We repel the heat of the one with the coolness of the other, and the coolness of the other with the heat of the one" (Abu Dawud 3836, at-Tirmidhi 1843; authenticated). The professor cites it from the Sahih collections, but it is found in Abu Dawud and at-Tirmidhi; its authenticity is established. The lesson goes beyond watermelon: Ibn al-Qayyim sees in it a principle of the entire prophetic dietetics, correcting a food with its opposite. The fresh date is warm and sweet, it warms and can overheat; watermelon is cold and moist, it cools and can chill the stomach; together, they balance each other. We find this pairing at Ramadan: dates at iftar, watermelon afterward. Ibn al-Qayyim adds that watermelon "cleanses the stomach and promotes urination," that it should be eaten before the meal and not after (otherwise it "spoils" what is in the stomach), and that on a completely empty stomach it can harm an empty stomach; hence the wisdom of pairing it with dates.
What watermelon provides
| In 300 g of flesh | Amount | What for |
|---|---|---|
| Water and minerals | 275 ml of water, potassium, a little magnesium and sodium | Hydration during fasting and summer, as the professor explains; one slice is worth a large glass of mineral water |
| Lycopene | 12 to 20 mg, more than tomato, and in a well-absorbed form | Antioxidant for the heart, prostate, and skin, according to the review on watermelon lycopene (EXCLI J, 2014) |
| Citrulline | 300 to 700 mg (more in the white part of the rind) | Converted into arginine and then into nitric oxide, which dilates blood vessels: this is the mechanism behind "stimulates the heart" and "erection problems" |
| Vitamins C and B6, beta-carotene | A third of vitamin C needs | The professor's "energy metabolism"; B6 helps with nausea and fatigue |
| Sugars | 18 to 20 g (glucose, fructose) | High glycemic index but moderate load, since it's very diluted; a diabetic should have one slice, not a quarter |
What the trials have measured
- Blood pressure. A meta-analysis of 15 randomized trials: citrulline supplementation lowers systolic pressure by about 7 mmHg and diastolic by 4 mmHg (J Hum Hypertens, 2019). And watermelon itself: in a 2025 dose-response trial in adults with elevated blood pressure, daily consumption of watermelon flesh reduced ambulatory blood pressure, more so at higher doses (Nutrients, 2025).
- Erectile function. Oral citrulline improved erectile function in men for whom the usual medications were not enough, in a randomized trial (Sex Med, 2018). Watermelon is not a medication, but the mechanism the professor cites is real, and eating the white part of the rind, the richest in citrulline, is not a whim.
- The seeds. Analysis of watermelon seeds shows a composition rich in protein, unsaturated fatty acids, zinc, and magnesium, and an oil with no toxicity in animals that improves the lipid profile (J Food Biochem, 2021). Roasted and salted, they are a common snack in the Middle East and Africa; in capsule form, they mainly provide zinc and citrulline.
In practice, and during Ramadan
- At iftar: two or three dates and water, the prayer, then one or two slices of watermelon before the meal; this is the pairing from the hadith, and Ibn al-Qayyim's order (before the meal, not after).
- At suhur: a slice of watermelon with talbina or bread, to start with a reserve of water and minerals; avoid excess salt alongside it, which promotes urination.
- Summer: as an afternoon snack, cool but not ice-cold; the juice blended with a little mint and lemon, drunk right away.
- The seeds: rinsed, dried, roasted for ten minutes in a pan with a pinch of salt; one handful.
- The white rind: as pickles or grated into a salad, it's the part richest in citrulline.
- Choosing one: heavy for its size, a well-marked yellow spot on the ground, a hollow sound when tapped; once cut, it keeps for two days in the fridge, covered.
Contraindications and precautions
A diabetic should count watermelon as a sweet fruit: a 200 g slice, no more, within a meal, and never as juice. Ibn al-Qayyim advises against it on an empty stomach and in excess (it cools and causes bloating): eat it with dates or at the start of a meal, in measured amounts. Its potassium content means it should be avoided in cases of severe kidney failure. Seed or citrulline capsules should not be taken with erection medications or nitrate derivatives without medical advice (drop in blood pressure). A cut watermelon left out spoils quickly: keep it in the fridge, two days.
Frequently asked questions
What does the hadith say about watermelon?
That the Prophet ﷺ ate it with fresh dates, saying: "we repel the heat of the one with the coolness of the other" (Abu Dawud, at-Tirmidhi). This is the rule of balancing a food with its opposite.
What are the benefits of watermelon for men?
Its citrulline converts into nitric oxide, which dilates blood vessels: blood pressure drops (meta-analysis) and erectile function improves in trials. Its seeds provide zinc. It's a good fruit, not a treatment.
Can watermelon be eaten during Ramadan?
It's the ideal fruit for fasting: 92% water and minerals. After the dates at iftar, before the meal; and at suhur for the water reserve. Not ice-cold, not in excess.
Can watermelon seeds be eaten?
Yes, roasted and lightly salted, as in the Middle East: protein, zinc, magnesium, good fatty acids. One handful as a snack; in capsules, on medical advice.
Can a diabetic eat watermelon?
A 200 g slice within a meal, no more, and not as juice: its glycemic index is high but its sugar load per serving remains moderate thanks to its water content.
