Does Watermelon Have Citrulline in It?

November 24, 2025 •

4 min read

Watermelon is the most significant natural plant source of L-citrulline, an amino acid that can benefit cardiovascular health. The name 'citrulline' itself was derived from the Latin word for watermelon, Citrullus, from which it was first extracted. This nutrient-rich fruit provides a valuable dietary source of this non-essential amino acid, important for various bodily functions.

Quick Summary

Watermelon is a rich source of the amino acid L-citrulline, which the body converts into L-arginine and subsequently nitric oxide to support cardiovascular function and athletic performance. The rind contains a higher concentration of citrulline than the flesh, although factors like cultivar and color can cause significant variation. Cooking and pasteurization can impact the bioavailability of citrulline in the fruit.

Key Points

Natural Source of Citrulline: Watermelon is a rich natural source of the non-essential amino acid L-citrulline, from which its scientific name, Citrullus, was derived.
Highest Concentration in Rind: While the flesh contains citrulline, the highest concentration is found in the white rind, which is often discarded.
Cardiovascular Benefits: L-citrulline is converted to L-arginine and then to nitric oxide, which helps relax blood vessels and can lower blood pressure, especially in individuals with prehypertension.
Enhanced Athletic Performance: The vasodilatory effects of nitric oxide can improve blood flow and oxygen delivery to muscles, potentially enhancing endurance and reducing muscle soreness.
Bioavailability Advantage: Citrulline from watermelon, consumed in its natural food matrix, may have higher bioavailability compared to some synthetic supplements.
Variations in Content: Citrulline levels differ based on the part of the fruit, cultivar (variety), ripeness, and processing methods like pasteurization.
Beyond Supplements: Consuming watermelon provides a holistic nutritional profile, including antioxidants like lycopene and other vitamins, which offer additional health advantages.

Yes, Watermelon is a Primary Source of Citrulline

Watermelon (Citrullus lanatus) is a powerhouse of nutrients, and for those interested in the non-proteinogenic amino acid citrulline, it is a key dietary source. The body naturally produces some citrulline, primarily in the gut, where it is used as an intermediate in the urea cycle to remove ammonia from the body. However, the citrulline derived from watermelon is particularly beneficial because of its high bioavailability when consumed in its natural food matrix.

How Watermelon's Citrulline Benefits the Body

The main health benefits of consuming citrulline from watermelon are linked to its role as a precursor to another amino acid, arginine. In the kidneys, citrulline is converted into arginine, which is then used by the endothelial cells lining the blood vessels to produce nitric oxide. Nitric oxide is a potent vasodilator, meaning it relaxes and widens blood vessels, leading to improved blood flow and potential health improvements.

Here's a breakdown of how it works:

Step 1: Ingestion. You consume watermelon, which is rich in L-citrulline.
Step 2: Absorption. The citrulline is absorbed in the small intestine, where it bypasses first-pass metabolism in the liver.
Step 3: Conversion. The kidneys efficiently convert the L-citrulline into L-arginine.
Step 4: Production. The body uses the increased L-arginine to produce more nitric oxide.
Step 5: Vasodilation. The nitric oxide relaxes your blood vessels, improving overall circulation.

Concentration of Citrulline Varies by Watermelon Part

Not all parts of the watermelon contain the same amount of citrulline. Research has consistently shown that the rind, often discarded, contains higher concentrations of citrulline on a dry weight basis than the sweet, red flesh. This makes watermelon rind, when prepared correctly, a valuable source of this amino acid and a potential use for food waste. The concentration can also vary depending on the variety and color of the flesh, with some studies indicating that yellow-fleshed watermelons might contain more citrulline than red-fleshed ones.

Comparison of Citrulline Content


Watermelon Part	Relative Citrulline Content (Fresh Weight)	Bioavailability	Potential Use
Flesh (Red)	Lower	Moderate	Consumed fresh for hydration and taste, contains antioxidants like lycopene.
Flesh (Yellow)	Potentially Higher	Good	Consumed fresh, noted to sometimes have higher citrulline than red varieties.
Rind (White part)	Higher (Dry weight basis)	High, potentially better than isolated supplements.	Can be pickled, juiced, or used in extracts; often underutilized.
Seeds	Varies, can be low to high	Low; often requires processing.	Processed into flour or oil; less concentrated source for typical consumption.

Benefits of Citrulline from Watermelon

While citrulline supplements are widely available, obtaining it from whole-food sources like watermelon offers several advantages due to the fruit's complex nutritional matrix. Watermelon contains other beneficial compounds, such as the antioxidant lycopene, and vitamins and minerals that can work synergistically to provide additional health benefits.

Cardiovascular Health

Studies on watermelon extract and juice consumption have shown promising results for cardiovascular health, especially in individuals with prehypertension or hypertension. The increased nitric oxide bioavailability can help reduce blood pressure and improve arterial stiffness. However, it's important to note that studies have used concentrated extracts or powder to achieve a high enough dose for a measurable effect, which might be difficult to attain from consuming fresh watermelon alone.

Athletic Performance and Recovery

For athletes, citrulline is known for its potential to improve exercise performance and reduce muscle soreness. By enhancing blood flow and oxygen delivery to muscles, citrulline can help reduce fatigue during intense exercise. Some studies have found that citrulline supplementation can increase endurance during strength training and improve recovery time. However, the effective dosage for performance enhancement is typically higher than what one would get from a regular serving of watermelon.

Digestive and Immune Function

Beyond its effect on the cardiovascular system and athletic performance, citrulline is crucial for the urea cycle, which helps the body process and excrete waste products. Furthermore, some research suggests a link between citrulline and immune function, especially in inflammatory conditions. As a biomarker, citrulline levels can also be an indicator of intestinal function and mucosal mass.

Conclusion: More than Just a Sweet Treat

Watermelon is indeed a rich source of citrulline, and the presence of this amino acid is a primary reason for the fruit's association with improved cardiovascular health and enhanced athletic performance. The concentration of citrulline is highest in the rind, a part of the fruit often overlooked. While consuming fresh watermelon provides beneficial amounts of citrulline, achieving therapeutic dosages typically requires more concentrated forms, such as extracts or powders. Still, incorporating watermelon into your diet offers a natural and delicious way to support your body's production of nitric oxide and enjoy a wide range of other nutrients, like antioxidants and vitamins.

Factors Influencing Watermelon's Citrulline Content

Cultivar and Genetics

Different varieties of watermelon contain varying levels of citrulline. Genetic factors, along with growing conditions and ripeness, can influence the final concentration. Research into watermelon genetics and breeding is ongoing to develop cultivars with higher amounts of beneficial compounds, including citrulline.

Processing and Storage

Processing methods can also affect the bioavailability of citrulline. Studies have shown that thermal treatments like pasteurization can reduce the citrulline content in watermelon juice. Conversely, research suggests that citrulline within the fruit's natural food matrix may be absorbed more efficiently than synthetic citrulline supplements. Freezing may help preserve citrulline content in processed watermelon products.

Ripeness

Some studies suggest that citrulline content can accumulate as the watermelon ripens, peaking alongside sugar content. However, the relationship between ripeness and citrulline levels can be complex and may vary depending on the specific cultivar.

Frequently Asked Questions

Citrulline is a non-essential amino acid that plays a vital role in the body's metabolism and cardiovascular health. It is a precursor to nitric oxide, a compound that helps relax blood vessels to improve blood flow, and is also involved in the urea cycle for removing waste.

The highest concentration of citrulline is found in the white rind of the watermelon, not the red or yellow flesh. However, the amount can vary between cultivars, and the flesh still contains a beneficial amount of the amino acid.

While watermelon contains citrulline that can enhance blood flow, the amount needed for a significant ergogenic (performance-enhancing) effect is typically higher than what is found in a regular serving of the fruit. High-concentration watermelon extracts or supplements are often used in studies demonstrating athletic benefits.

Yes, watermelon juice contains L-citrulline. However, the citrulline content can be reduced during pasteurization, a common food processing technique. Fresh, unpasteurized juice would contain more of the amino acid.

Some research suggests that citrulline consumed within the natural food matrix of watermelon may have higher bioavailability compared to purified supplements. The presence of other compounds like antioxidants and amino acids in the fruit may contribute to enhanced absorption and effects.

Some studies show that supplementation with watermelon extract, providing concentrated citrulline, can help lower blood pressure in individuals with prehypertension or hypertension. The effect comes from the citrulline being converted to nitric oxide, which relaxes blood vessels.

Yes, citrulline levels can differ based on the flesh color. Some studies have found that yellow or orange-fleshed watermelons may contain slightly more citrulline than red-fleshed varieties on a dry weight basis.