How much citrulline is in a watermelon?

December 21, 2025 •

3 min read

Studies have shown that watermelon is the richest known dietary source of the amino acid L-citrulline. The exact quantity of citrulline in a watermelon varies significantly depending on the variety, ripeness, and the specific part of the fruit you consume.

Quick Summary

The amount of citrulline in watermelon depends on the variety and part of the fruit, with the rind often containing higher concentrations than the red flesh, especially on a dry weight basis. Growing conditions also play a role, influencing the final content.

Key Points

Rind has more citrulline by dry weight: The white rind of a watermelon typically contains a higher concentration of citrulline than the red flesh, especially when measured on a dry weight basis.
Yellow watermelon can be richer: Some research indicates that yellow or orange-fleshed varieties may contain higher citrulline levels than their red counterparts.
Content varies widely: The citrulline concentration is influenced by the watermelon's variety, ripeness, and even its growing conditions, so values are not consistent across all fruit.
Citrulline boosts nitric oxide: In the body, citrulline is converted into L-arginine, which then promotes nitric oxide production, leading to better blood flow.
Consider the rind and juice for higher intake: To maximize dietary citrulline, use the white rind in recipes like pickles or smoothies, and consider watermelon juice or extracts for a more concentrated source.
Supplements offer concentrated dosage: For targeted therapeutic benefits, concentrated watermelon extracts or supplements can provide higher, more consistent doses of citrulline than whole fruit.

The Surprising Citrulline Content of Watermelon

Watermelon, a member of the Cucurbitaceae family, is a natural and abundant source of the non-essential amino acid L-citrulline. The name "citrulline" is derived from the Latin word for watermelon, Citrullus, highlighting this deep connection. While many people associate watermelon with its juicy, red flesh, it is the less-consumed rind that often packs a more concentrated punch of this valuable nutrient.

Factors Influencing Citrulline Concentration

Pinpointing the precise quantity of citrulline in any given watermelon is complex because several factors affect the final amount. Research reveals that concentrations can vary greatly. Here are some of the most influential factors:

Watermelon variety: Different cultivars contain vastly different amounts of citrulline. Some studies show yellow or orange-fleshed varieties may have higher concentrations than traditional red-fleshed types. Specific cultivars like 'Crimson Sweet' and 'Dixielee' have been identified as having notably high citrulline levels.
Flesh vs. Rind: On a dry weight basis, the rind of the watermelon consistently shows a higher concentration of citrulline than the red flesh. On a fresh weight basis, some studies have found the flesh to contain higher levels, but this can vary. The distinction between dry and fresh weight is crucial when interpreting research findings.
Ripeness: The concentration of citrulline can peak at different stages of ripeness. This means that a perfectly ripe watermelon may not necessarily be the most citrulline-dense.
Growing Conditions: The environmental factors under which a watermelon is grown can significantly affect its nutritional profile. A study comparing watermelons grown in different locations found large variations in L-citrulline concentration, suggesting that climate and soil conditions play a role.

The Role of Citrulline and the Arginine Pathway

Citrulline's primary health benefit stems from its unique role in the body. When consumed, L-citrulline is converted to L-arginine, a precursor to nitric oxide (NO). Nitric oxide is a powerful vasodilator, a compound that helps relax and widen blood vessels, promoting better blood flow. This improved circulation can benefit cardiovascular health, exercise performance, and may even aid in managing conditions like erectile dysfunction.

Unlike supplementing directly with L-arginine, ingesting citrulline is more effective at raising plasma arginine levels because citrulline bypasses metabolism in the gut and liver. This makes watermelon a highly bioavailable source of the compound, ensuring that more citrulline successfully enters the bloodstream to be converted.

Citrulline Content: A Comparison of Watermelon Varieties and Parts

To better understand the variance, here is a comparison based on research findings. It is important to note these are representative values and can change based on the factors listed above.


Watermelon Part / Type	Representative Citrulline Content (mg/g fresh weight)	Notes
Yellow Watermelon Flesh	~3.5 mg/g	Often cited as having one of the highest concentrations in the flesh.
Red Watermelon Flesh	~1.0–2.1 mg/g	Most common variety, offers a moderate amount.
Watermelon Rind (inner white part)	~0.8–2.0 mg/g	Contains a significant amount and can be higher than the flesh on a dry weight basis.
Watermelon Juice (from flesh)	~2.46 mg/mL	A concentrated source, though citrulline may degrade with processing.
Watermelon Extract/Powder	Highly variable	Dependent on the concentration process; can deliver high doses for supplementation.

Maximizing Your Citrulline Intake from Watermelon

If you want to boost your intake, simply eating the red, sweet flesh is a good start. However, to maximize the citrulline, consider incorporating the white rind into your diet. The rind is edible and can be pickled, juiced, or blended into smoothies. Another effective method is to use watermelon juice, as the concentration process can increase the density of the compound. For athletes or individuals requiring higher therapeutic doses for blood pressure support, extracts and powders, which are processed to concentrate the citrulline, may be necessary. For more information on the nutrient profile of watermelon, see the resources provided by institutions like the University of Rochester Medical Center.

Conclusion

In summary, the amount of citrulline in a watermelon is not a single, fixed number but varies depending on the cultivar, ripeness, and the part of the fruit consumed. The watermelon rind is a surprisingly potent source of this amino acid, often containing higher concentrations than the flesh, particularly on a dry weight basis. Incorporating more of the rind or opting for concentrated juices can increase intake, which offers benefits ranging from improved circulation to enhanced athletic performance due to citrulline's conversion to nitric oxide in the body. While red flesh is a good source, exploring different varieties and the often-discarded rind can unlock even greater nutritional potential.

Frequently Asked Questions

The highest concentration of citrulline is typically found in the white rind of the watermelon, particularly when measured on a dry weight basis. While the flesh also contains citrulline, the rind is a more potent source.

Some studies suggest that yellow or orange-fleshed watermelons may have slightly more citrulline than the common red-fleshed varieties. However, the exact amount varies depending on the specific cultivar and growing conditions.

Citrulline from watermelon is converted into L-arginine and then to nitric oxide in the body. This helps dilate blood vessels, which can improve blood flow, support cardiovascular health, and potentially enhance exercise performance.

For exercise benefits, studies show mixed results from eating whole watermelon, as the volume required to get a clinically effective dose of citrulline can be very large. Highly concentrated juices or supplements may be more reliable for a specific athletic boost.

Yes, some food processing methods, like pasteurization for juice, can lead to a reduction in citrulline content. Freeze-drying or microencapsulation are used by some manufacturers to concentrate and preserve the citrulline.

When you ingest citrulline, your body efficiently converts it to the amino acid L-arginine. This conversion happens in the kidneys and increases plasma arginine levels more effectively than supplementing with arginine directly.

Yes, although watermelon is the richest source, other related foods in the Cucurbitaceae family, such as cucumbers, gourds, and pumpkins, also contain lower levels of citrulline.