Watermelon (Tarbuj)
92% water, citrulline for athletic performance and blood pressure, more lycopene than raw tomatoes, and edible seeds you should stop discarding.
TLDR — What You Need to Know
- Watermelon is 92% water by weight — the single most hydrating common fruit, superior to cucumber for electrolyte replacement during heat
- Citrulline (250mg per 100g) is an amino acid that converts to arginine in the kidneys, which then produces nitric oxide — a vasodilator that lowers blood pressure and improves blood flow to muscles during exercise
- Lycopene content (4532µg per 100g) is higher than raw tomatoes — and unlike tomato, watermelon lycopene is naturally in a more bioavailable form
- Watermelon seeds are nutritious — they contain zinc, magnesium, protein, and healthy fats. Do not discard them; eat with the fruit or dry-roast as a snack
- Despite popular belief, watermelon is safe for diabetics in controlled portions — the GI is high (72) but glycaemic load is very low (4) because of the very high water content
- Whole watermelon stored at room temperature retains more lycopene than refrigerated watermelon — refrigeration slows carotenoid synthesis after harvest
Why Watermelon Is One of India’s Best Summer Fruits
Watermelon (Citrullus lanatus) is one of the most consumed summer fruits in India — and for good biological reasons. It arrives precisely when the body needs it most: during the hot months of March through June when temperature-related dehydration, heat exhaustion, and electrolyte loss are genuine health concerns.
India grows watermelons across Andhra Pradesh, Karnataka, Tamil Nadu, Maharashtra, and Uttar Pradesh. The large, dark-green striped varieties dominate the market, though yellow-fleshed and mini watermelon varieties are increasingly available.
Watermelon is unusual among fruits in that almost all of it is edible and useful:
- The red flesh: Primary eating part — contains the water, lycopene, citrulline, sugars
- The seeds: Nutritious — contain zinc (2.9mg per 100g dried), magnesium, protein (28g per 100g dried), linoleic acid
- The white rind: Edible and used in Indian cooking (watermelon rind pickle, sabzi) — contains citrulline in higher concentrations than the flesh
- The green outer skin: Not typically eaten but compostable
Nutritional Profile
Watermelon — Nutrition Facts per 100g (red flesh, raw)
Per 100g watermelon flesh (approximately a 200g thick slice)
| Nutrient | Amount | % Daily Value |
|---|---|---|
| Energy | 30 kcal | — |
| Water | 91.5 g (91.5%) | — |
| Protein | 0.6 g | — |
| Total Fat | 0.2 g | — |
| Carbohydrates | 7.6 g | 3% |
| of which sugars | 6.2 g | — |
| Dietary Fibre | 0.4 g | 1% |
| Vitamin C | 8 mg | 13% |
| Citrulline | 250 mg/100g (rind: 1500mg) | — |
| Lycopene | 4532 µg | — |
| Beta-carotene | 303 µg | — |
| Potassium | 112 mg | 2% |
| Magnesium | 10 mg | 2% |
Health Benefits — What Does the Science Say?
1. Citrulline — nitric oxide, blood pressure, and athletic performance
Citrulline is a non-essential amino acid found in very high concentrations in watermelon — 250mg per 100g in the flesh and up to 1500mg per 100g in the white rind. The citrulline-to-arginine pathway is:
Citrulline → (kidney enzymes) → Arginine → (eNOS enzyme in endothelium) → Nitric Oxide (NO)
Nitric oxide causes relaxation and vasodilation of smooth muscle in blood vessel walls, resulting in:
- Lower blood pressure: Multiple randomised trials show watermelon extract supplementation (equivalent to about 500g watermelon daily) significantly reduces both systolic and diastolic blood pressure in prehypertensive adults (Figueroa et al., Hypertension 2012)
- Improved exercise performance: NO-mediated vasodilation increases oxygen and nutrient delivery to working muscles; studies show watermelon juice consumption before exercise reduces muscle soreness and improves recovery
- Erectile function: NO is the primary mediator of penile erection; watermelon has been called a “natural Viagra” in popular media — while the dose from watermelon alone is insufficient to be a clinical treatment, the biological pathway is real
The rind is particularly rich in citrulline — watermelon rind pickle (a traditional Indian preserve) is a surprisingly good source.
2. Lycopene — prostate health and beyond
Lycopene is a carotenoid that gives watermelon and tomatoes their red colour. Watermelon contains 4532µg per 100g — significantly more than raw tomatoes (2573µg per 100g) and comparable to cooked tomatoes.
Uniquely, watermelon lycopene is in the all-trans isomeric form, which is more bioavailable than the predominantly cis-form in tomatoes. Additionally, watermelon lycopene requires no cooking (unlike tomatoes, where cooking increases lycopene bioavailability) — it is readily absorbed from fresh watermelon.
Lycopene’s documented health associations:
- Prostate cancer: The strongest evidence for dietary lycopene is for reduced prostate cancer risk (multiple epidemiological studies, though causation not fully proven)
- Cardiovascular: Reduces LDL oxidation and vascular inflammation
- Skin photoprotection: Accumulates in skin tissue and provides mild UV protection from within
- Bone health: Associated with reduced fracture risk in some studies
3. Hydration and electrolyte replacement
At 91.5% water by weight, watermelon is the most hydrating common fruit. But hydration is not just about water — it requires electrolytes to facilitate cellular water retention. Watermelon provides potassium (112mg/100g), a modest amount of sodium (naturally), and magnesium — the key electrolytes lost through sweat.
In India’s summer heat (40–45°C in many regions), electrolyte loss through sweating can be significant. Watermelon provides a much gentler electrolyte and fluid replacement than oral rehydration solutions for non-clinical dehydration.
4. Watermelon seeds — stop discarding them
Watermelon seeds are significantly nutritious per gram:
- Zinc: 2.9mg per 100g dried seeds — supports immune function, wound healing, testosterone production
- Magnesium: 136mg per 100g dried seeds — muscle and nerve function
- Protein: 28g per 100g dried seeds — complete amino acid profile
- Linoleic acid: Healthy omega-6 fat
The small seeds in fresh watermelon are edible whole. Larger seeds can be dried and dry-roasted with salt as a nutritious snack. Many traditional Indian communities have always eaten the seeds; the modern seedless watermelon trend discards this nutritional value.
Side Effects and Cautions
Frequent urination. The very high water content (900ml in a 1kg watermelon slice) makes frequent urination predictable. Not a health concern but worth noting before long trips or meetings.
Natural sugars and diabetics. Watermelon has a high GI (72) because the sugars present are rapidly absorbed. However, the glycaemic load per typical serving is very low (GL ≈ 4 per 100g) because 91.5% of the weight is water. A 200g serving (a generous slice) provides only about 12g of carbohydrates and a GL of approximately 8 — manageable for most diabetics. Portion size is the key factor.
Potassium and kidney disease. Patients with chronic kidney disease (CKD) stages 4–5 who are on potassium-restricted diets must moderate watermelon — the potassium content (112mg/100g) can be significant in large portions.
FODMAP concern for IBS. Watermelon contains fructose and some FODMAP compounds. People with irritable bowel syndrome (IBS) following a low-FODMAP diet should limit watermelon to small servings (about 150g) to avoid triggering symptoms.
Storage
- Whole watermelon at room temperature: 2–3 weeks. Importantly, room temperature storage continues the lycopene synthesis process — refrigerating whole watermelons stops carotenoid development.
- Cut watermelon: Refrigerate immediately in an airtight container. Use within 3–4 days.
- Avoid re-cutting and re-storing repeatedly: Each cut increases surface area for bacterial growth.
- Freeze: Cut watermelon into cubes and freeze — use in smoothies, slushes. Texture becomes soft after thawing.
Watermelon vs Muskmelon vs Cucumber
Watermelon vs Muskmelon vs Cucumber — Hydration and Summer Nutrition
| Parameter | Watermelon | Muskmelon (Kharbooja) | Cucumber |
|---|---|---|---|
| Water content | 91.5% | ~90% | 96% |
| Calories per 100g | 30 kcal | 34 kcal | 16 kcal |
| Potassium per 100g | 112mg | 267mg | 147mg |
| Lycopene | 4532µg (high) | None | None |
| Beta-carotene | 303µg | 2020µg (high) | 45µg |
| Citrulline | 250mg (significant) | Trace | Trace |
| Natural sugar | 6.2g | 8.2g | 1.7g (very low) |
| Glycaemic index | 72 (high, low GL) | 65 (medium) | 15 (very low) |
| Vitamin C | 8mg | 18mg | 3mg |
| Best for | Lycopene, citrulline, hydration | Vitamin A, potassium, cooling | Low-calorie hydration, digestion |
Data: USDA FoodData Central; IFCT 2017. GI values from International GI Tables (Foster-Powell et al.).
Recipes
Watermelon Juice with Mint and Black Salt
Simple watermelon juice with fresh mint and black salt — a classic Indian street-side drink that enhances the electrolyte content naturally. Include the juice from the inner rind for extra citrulline. No added sugar needed if watermelon is ripe.
Key Ingredients
500g watermelon flesh and inner rind (white part included) · 8-10 fresh mint leaves · 1/4 tsp black salt (kala namak) · Small pinch of roasted cumin powder · 1 tsp lemon juice (optional) · Ice cubes
Watermelon Feta Salad (Indian Style)
A refreshing salad pairing watermelon with crumbled paneer (substituting feta), cucumber, and chaat masala. The natural sweetness of watermelon contrasts with the salty paneer. A modern Indian take on the Mediterranean watermelon-feta combination.
Key Ingredients
400g watermelon cubes (seeds included) · 100g fresh paneer (crumbled) · 1/2 cucumber (diced) · Small red onion (thinly sliced) · 1/4 tsp chaat masala · Fresh mint leaves · 1 tsp lemon juice · Pinch of black salt
Adulteration Test
Home Test: Artificial Colour Injection in Watermelon
Steps
- 1 Cut the watermelon and examine the flesh colour — naturally red-fleshed watermelon has uneven colour intensity with lighter areas near seeds and slightly paler flesh near the rind
- 2 Look for needle marks or discolouration near the rind — injected watermelons often show entry points near the stem end or have uneven colour distribution with very dark streaks
- 3 Place a small piece of flesh in a glass of water and stir — artificial colour will leach into the water, turning it pink or red; natural watermelon pigment (lycopene) does not significantly colour the water
- 4 Taste the flesh near the rind — artificially sweetened watermelons sometimes taste unnaturally sweet throughout including the rind area; natural watermelons are sweet in the centre and bland near the rind
Pure / Pass
Uneven natural red colour, no needle marks, water remains clear after flesh is placed in it, rind area tastes bland — naturally grown watermelon.
Adulterated / Fail
Uniformly intense red or pink colour, suspicious marks near rind, water turns pink-red, entire flesh including rind is sweet — possible colour injection or sugar injection.
Available at Organic Mandya
Fresh Watermelon
Summer-harvested watermelon. Naturally grown, no artificial sweetening or colouring.
Frequently Asked Questions
Q Can diabetics eat watermelon?
Can diabetics eat watermelon?
Yes, in moderate portions. Despite a high GI (72), watermelon has a very low glycaemic load (about 4 per 100g) because 91.5% of its weight is water and carbohydrate content is only 7.6g per 100g. A 200g serving provides about 12g carbohydrates — manageable for most diabetics. Eat as part of a meal with protein to further reduce glucose impact. Monitor individual blood glucose response.
Q What is citrulline in watermelon and why does it matter?
What is citrulline in watermelon and why does it matter?
Citrulline is an amino acid in watermelon (250mg per 100g flesh, much more in the rind) that the body converts to arginine, which then produces nitric oxide. Nitric oxide relaxes and widens blood vessels — lowering blood pressure, improving blood flow to muscles during exercise, and reducing post-exercise soreness. Clinical studies have shown watermelon supplementation reduces blood pressure in prehypertensive adults.
Q Should I eat watermelon seeds?
Should I eat watermelon seeds?
Yes. Watermelon seeds are nutritious and safe to eat. Fresh seeds can be eaten with the fruit. Larger seeds can be dried and dry-roasted with salt as a snack. They contain zinc (important for immunity and testosterone), magnesium, protein, and healthy fats. The trend toward seedless watermelons eliminates this nutritional bonus. Traditional farming and consumption in India always included eating the seeds.
Q Why does watermelon have more lycopene than tomatoes?
Why does watermelon have more lycopene than tomatoes?
Watermelon contains 4532µg of lycopene per 100g compared to approximately 2573µg in raw tomatoes. Additionally, watermelon lycopene is predominantly in the all-trans isomeric form, which is more bioavailable than the forms in tomatoes. Unlike tomatoes, watermelon lycopene does not require cooking to enhance bioavailability — it is readily absorbed from fresh fruit.
Last updated: March 2026
Disclaimer: This article is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your doctor or a qualified healthcare provider before making dietary changes, especially if you have a medical condition.