Watermelon: The Unequivocal Winner
By a significant margin, watermelon is the fruit that contains the most citrulline. The name citrulline is even derived from Citrullus vulgaris, the Latin term for watermelon. This amino acid is a precursor to L-arginine, which the body uses to create nitric oxide, a compound that helps relax blood vessels, improve blood flow, and lower blood pressure. Different parts and varieties of watermelon can have varying concentrations of citrulline, but it remains the top dietary source.
Citrulline Content Varies by Watermelon Variety
Not all watermelons are created equal when it comes to their citrulline content. Several factors, including the type of watermelon, its ripeness, and the specific tissue (flesh versus rind), can affect the concentration.
- Yellow-fleshed watermelons: Some yellow-fleshed varieties have been found to contain higher citrulline levels than their red counterparts on a fresh weight basis, sometimes reaching up to 3.5 mg per gram of flesh.
- Red-fleshed watermelons: While generally lower than yellow varieties, red watermelons still contain substantial amounts of citrulline. Popular red varieties like 'Crimson Sweet' and 'Dixielee' are high in the amino acid.
- Seedless vs. seeded: Studies have shown that seedless watermelons can have slightly more citrulline than seeded ones on a fresh weight basis.
- Rind vs. flesh: While most people discard the rind, it is surprisingly rich in citrulline, especially when measured by dry weight. However, due to its high water content, the flesh provides more total citrulline in a typical serving. The rind can be a valuable source if utilized, perhaps in smoothies or pickled dishes.
Other Fruits Containing Citrulline
While watermelon is the richest source, other fruits, particularly those within the same family, also contain citrulline. The Cucurbitaceae family includes melons, squash, and pumpkins. The citrulline concentration in these alternatives is considerably lower, ranging from 7 to 41 times less than in watermelon, but they still contribute to your overall intake.
- Melons: Casaba melon and mouse melon are known to contain citrulline, though in smaller quantities.
- Cucumber: This common vegetable (botanically a fruit) contains citrulline and is part of the Cucurbitaceae family.
- Pumpkin and Squash: These gourds also contain traces of citrulline, alongside other beneficial compounds like beta-carotene.
- Bitter Melon: The arils, or fleshy seed coverings, of bitter melon have been identified as a source of citrulline.
- Horned Melon: Similar to bitter melon, the rind of the horned melon contains more citrulline than its flesh.
Health Benefits of Citrulline from Fruit
Citrulline's primary health benefit stems from its role as a precursor to L-arginine and subsequently, nitric oxide. This pathway contributes to several positive physiological effects:
- Cardiovascular Health: The increase in nitric oxide production from citrulline promotes vasodilation, which is the widening of blood vessels. This can help lower blood pressure and improve overall heart health.
- Improved Exercise Performance: Citrulline supplementation has been shown to enhance athletic performance, particularly for strength and anaerobic exercise. It can help reduce muscle soreness and improve oxygen delivery to muscles during workouts.
- Erectile Function: By increasing blood flow through nitric oxide production, citrulline can help with achieving and maintaining erections.
- Antioxidant Properties: Citrulline has demonstrated antioxidant properties, protecting cells from oxidative damage.
Comparing Citrulline Content in Fruits
The following table provides a general comparison of citrulline levels based on fresh weight. Concentrations can vary significantly based on the cultivar, ripeness, and growing conditions.
| Fruit/Part | Typical Citrulline Concentration (per kg fresh weight) | Citation(s) |
|---|---|---|
| Watermelon (Yellow Flesh) | ~3.5 grams (some varieties) | |
| Watermelon (Red Flesh) | ~1.0–2.4 grams (some varieties) | |
| Watermelon Rind | ~0.8–1.5 grams | |
| Casaba-Type Melon | ~0.86 grams | |
| Mouse Melon | ~0.64 grams | |
| Horned Melon Rind | ~0.45 grams | |
| Cucumber | Very low levels; studies report up to 110 mg/kg |
How to Increase Your Citrulline Intake from Food
Incorporating more citrulline into your diet doesn't require a supplement. Watermelon is easily the most effective food source and can be enjoyed in a variety of ways. Here are some simple methods:
- Juice it: Fresh watermelon juice is a delicious and potent way to consume a concentrated dose of citrulline. Some studies show that citrulline is more bioavailable when consumed from juice rather than as a pure supplement.
- Eat the rind: The rind is a rich source of citrulline. Try pickling the rind or blending it into smoothies to reduce food waste and boost your intake.
- Combine with other citrulline-rich foods: While other fruits contain much less citrulline, combining them with watermelon or consuming them regularly still contributes to your overall dietary intake.
- Choose ripe fruit: Citrulline concentration tends to increase as watermelon ripens, so selecting perfectly ripe fruit is key.
Conclusion
When it comes to answering what fruit has the most citrulline, watermelon is the standout champion. Its high concentration of this beneficial amino acid, particularly in yellow-fleshed varieties and the often-discarded rind, makes it an exceptional food for boosting nitric oxide and supporting cardiovascular and athletic health. While other cucurbits like melon, pumpkin, and cucumber contain trace amounts, none come close to the powerhouse that is watermelon. By incorporating more watermelon and its rind into your diet, you can naturally and effectively increase your citrulline levels.
For more detailed information on citrulline's effects, consult a comprehensive review of clinical trials like this one: Effects of l-citrulline supplementation and watermelon consumption on longerterm and postprandial vascular function and cardiometabolic risk markers: A metaanalysis of randomised controlled trials in adults.
