Discover What Part of the Watermelon Has the Most Citrulline? The Surprising Answer for Nutrition and Diet

November 2, 2025 •

4 min read

Although commonly discarded, watermelon rind is a surprisingly rich source of the amino acid citrulline, which can sometimes exceed the concentration found in the sweet red flesh. The debate over exactly what part of the watermelon has the most citrulline highlights important nuances in nutrition, processing, and how we measure bioactive compounds, encouraging a second look at this functional food.

Quick Summary

Watermelon rind often contains a higher concentration of citrulline than the flesh, particularly when measured by dry weight. Bioavailability and overall health benefits are influenced by the specific part of the fruit, with the rind and even skin offering significant nutritional value.

Key Points

Rind is a citrulline powerhouse: Watermelon rind contains a high concentration of citrulline, particularly when measured on a dry weight basis.
Measurement methods matter: The conflicting findings on citrulline concentration (flesh vs. rind) are often a result of comparing dry weight measurements versus fresh weight.
Citrulline promotes circulation: When consumed, citrulline is converted to arginine, which increases nitric oxide levels, helping to dilate blood vessels and potentially lower blood pressure.
Variety influences content: Different watermelon cultivars, including those with yellow or orange flesh, can have varying amounts of citrulline.
Don't discard the rind: The rind is edible and versatile, able to be pickled, blended into smoothies, or stir-fried, offering a nutritional boost and reducing food waste.
Rind offers more than citrulline: The rind is also rich in fiber, which supports gut health, while the outer skin contains high levels of other antioxidants.

Understanding the Citrulline Content Controversy

Citrulline, a non-essential amino acid, was first isolated from watermelon, which is its richest natural dietary source. In the body, citrulline is converted into L-arginine, which is essential for synthesizing nitric oxide (NO). NO helps to relax and dilate blood vessels, which improves blood flow and can help lower blood pressure. For years, the white rind of the watermelon has been praised for its high citrulline content. However, scientific measurements have revealed a more complex story, with conflicting results often dependent on measurement methodology and other factors.

The Dry Weight vs. Fresh Weight Debate

Scientific studies comparing citrulline levels in watermelon parts often present different conclusions, primarily because of the distinction between dry weight (dw) and fresh weight (fw) measurements.

Dry Weight: Some studies found that the rind, when dehydrated, contains higher concentrations of L-citrulline than the flesh on a dry weight basis. This is significant because it indicates the rind is dense with the amino acid. For example, one study found the rind had 61.4 mg/100 g dry weight of citrulline, compared to the flesh's 39.7 mg/100 g.
Fresh Weight: Other recent studies, which compare citrulline content on a fresh weight basis (meaning the edible portion as-is, with high water content), found higher citrulline in the flesh than in the rind or skin. This is largely due to the much higher water content of the rind (around 95%) compared to the flesh (around 90%), effectively diluting the citrulline concentration in the rind by fresh weight.

Beyond measurement methods, other factors like the watermelon cultivar, flesh color, and even growing conditions (such as location and environmental stress) can cause variations in citrulline content. For instance, certain yellow or orange-fleshed varieties have been shown to contain higher citrulline levels than red-fleshed ones.

Health Benefits and Bioavailability of Citrulline

The health benefits of watermelon's citrulline are not just confined to the rind. The entire fruit offers advantages, but the dense concentration in the rind makes it a valuable, often-overlooked source. After consumption, citrulline from all parts of the watermelon is absorbed and converted to arginine, leading to nitric oxide production.

Cardiovascular Health: Increasing nitric oxide helps promote vasodilation, which improves blood flow and helps manage blood pressure in middle-aged and elderly individuals.
Athletic Performance: Citrulline supplementation is linked to improved athletic anaerobic performance and reduced muscle soreness post-exercise.
Bioavailability: The context of the food matrix is important. One in-vitro study found a slightly greater bioavailability (better absorption) of citrulline from the outer skin compared to the flesh or rind, potentially due to other synergistic compounds.

Using the Entire Watermelon for Maximum Citrulline Intake

To maximize citrulline intake and minimize food waste, incorporating the rind into your diet is a smart move. When preparing the rind, it's a good practice to peel away the tough, dark green outer layer, leaving the white portion to work with.

Here are some delicious and creative ways to eat watermelon rind:

Pickled: Watermelon rind pickles are a classic way to enjoy the firm, cucumber-like texture. They make a tangy and sweet addition to sandwiches or charcuterie boards.
Smoothies: For a convenient boost, cube and freeze watermelon rind. Add the frozen cubes to your next smoothie recipe for a refreshing, nutrient-rich addition that also helps thicken the drink.
Stir-fried: Treat the rind like a vegetable. When sautéed, it softens and readily absorbs other flavors from your stir-fry ingredients, offering a subtle, mild taste.
Juiced: Blend the rind along with the flesh to create a juice packed with citrulline. Adding a splash of lemon or lime can enhance the flavor profile.
Candied: Following a similar process to candying orange peels, you can create sweet watermelon rind candy by boiling the cubes in a sugar syrup and then dehydrating them.

Comparison: Watermelon Rind vs. Flesh


Aspect	Watermelon Rind (White Part)	Watermelon Flesh (Red/Sweet Part)	Watermelon Skin (Green Outer Peel)
Citrulline Concentration	High concentration (especially on dry weight basis).	High concentration (especially on fresh weight basis).	High bioavailability reported in some studies.
Fiber Content	High in fiber, supporting gut health.	Lower in fiber, primarily water and sugar.	High in total phenolic content and antioxidants.
Antioxidants	Contains antioxidants, though less than the skin.	Contains antioxidants, notably lycopene (in red varieties).	Highest antioxidant and total phenolic content.
Edibility/Texture	Firm, crunchy texture, similar to cucumber.	Soft, juicy, and sweet.	Tough and typically discarded, but edible.
Culinary Uses	Pickles, smoothies, stir-fries, candy.	Eaten fresh, salads, juices, purees.	Not typically consumed, but can be included in some recipes or extracts for max benefits.

Conclusion: Making the Most of Your Melon

While the sweet, juicy flesh is the star of the show for most, the science behind what part of the watermelon has the most citrulline reveals that the rind is a valuable, nutrient-rich powerhouse that should not be overlooked. Its high concentration of citrulline, especially on a dry weight basis, offers excellent cardiovascular benefits and can improve athletic performance. By creatively incorporating the rind into your diet, not only do you boost your intake of this beneficial amino acid, but you also take a meaningful step toward reducing food waste. The simplest path to getting more citrulline from your watermelon is to start by blending the rind into a smoothie or pickling it for a tangy treat. Embrace the whole melon and its full nutritional potential. You can learn more about reducing food waste by exploring resources on sustainable eating..

Frequently Asked Questions

Scientific findings differ based on measurement. On a dry weight basis, the rind often has a higher concentration of citrulline. However, on a fresh weight basis, the flesh might contain more, primarily because the rind has a significantly higher water content.

Yes, watermelon rind is completely edible and safe to eat. While the tough, green outer skin is typically peeled off, the white part is often used in culinary preparations. It has a texture and mild flavor similar to a cucumber.

Watermelon's citrulline is converted into L-arginine in the body, which helps produce nitric oxide. This improves blood flow by relaxing and widening blood vessels, potentially helping to lower blood pressure and improve athletic performance.

Yes, studies have shown that citrulline content can vary significantly depending on the watermelon variety. For example, some yellow or orange-fleshed varieties have been reported to contain higher citrulline levels than red-fleshed ones.

You can prepare watermelon rind in various ways. Popular options include pickling it for a tangy snack, blending it into smoothies for a fiber and nutrient boost, or stir-frying it as a vegetable.

The difference in citrulline content between seeded (diploid) and seedless (triploid) watermelons is not consistently significant. Some research indicates they have comparable levels, although variations exist based on other factors like cultivar and growing location.

Yes, watermelon juice is a good source of citrulline. However, the concentration can be affected by factors like processing. Some research indicates that consuming watermelon in its natural food matrix might offer better bioavailability than processed juices or supplements.