Is there citrulline in watermelon seeds? A complete guide

November 19, 2025 •

4 min read

While watermelon is the richest known source of the amino acid L-citrulline, the concentration of this compound varies significantly across its different parts. A recent study revealed that although citrulline is present in watermelon seeds, the amount is substantially lower than in the fruit's flesh and rind. This guide explains everything you need to know about the citrulline in watermelon seeds and where to find the highest concentrations.

Quick Summary

Watermelon seeds contain citrulline but in much lower concentrations than the flesh and rind. The rind is often the most potent source, and citrulline helps increase nitric oxide for cardiovascular health and athletic performance. However, seeds offer other valuable nutrients.

Key Points

Low Concentration: Watermelon seeds contain a very low concentration of citrulline compared to the fruit's flesh and rind.
Rind is Superior Source: The highest concentration of citrulline is typically found in the white rind of the watermelon.
Nutrient-Dense Seeds: Even without high citrulline, watermelon seeds offer other valuable nutrients like protein, magnesium, and healthy fats.
Bioavailability Matters: To absorb nutrients from seeds, they must be processed (e.g., roasted, sprouted) to break down their fibrous outer shell.
Supports Blood Flow: Citrulline increases nitric oxide production, which helps widen blood vessels to improve blood flow.
Not a Primary Source: Don't rely on unprocessed watermelon seeds for a meaningful citrulline boost; focus on the rind and flesh.

Do Watermelon Seeds Have Citrulline?

Yes, watermelon seeds contain citrulline, but research shows they are not the primary source of this amino acid within the fruit. The concentration in the seeds is significantly lower compared to the flesh and, most notably, the rind. For example, one study found that on a fresh weight basis, watermelon flesh had a much higher citrulline content (2.0–2.5 mg/g) than seeds (0.03–0.1 mg/g). This suggests that while citrulline is a component of the seeds, relying on them as a major dietary source is inefficient.

The low citrulline content in the seeds compared to the flesh and rind reflects the different physiological functions of these tissues within the plant. Citrulline can act as a nitrogen storage mechanism in the fruit tissue, while arginine is the primary nitrogen storage form in the seeds. Understanding this distribution is crucial for anyone interested in maximizing their citrulline intake from watermelon.

Where is the most citrulline in a watermelon?

For a reliable source of citrulline, you should turn your attention to the fruit's flesh and rind. Multiple studies have concluded that the rind, the white part between the green skin and the pink flesh, is particularly rich in citrulline, especially on a dry weight basis. Some findings suggest that while the flesh contains more citrulline on a fresh weight basis due to its higher moisture content, the rind is more concentrated per unit of dry matter. This makes watermelon rind an underutilized resource for citrulline, often discarded as waste. Yellow-fleshed and orange-fleshed watermelons might contain higher citrulline content than the more common red-fleshed varieties, with yellow being potentially the highest.

Why citrulline concentration matters

Citrulline's main benefit comes from its role as a precursor to L-arginine, which is converted to nitric oxide in the body. Nitric oxide is a powerful vasodilator, meaning it helps relax and widen blood vessels, which improves blood flow. This can have significant benefits for cardiovascular health and athletic performance by aiding in muscle recovery and reducing soreness. However, to achieve a meaningful therapeutic effect, a concentrated dose is often required, which is why supplements are common. Simply eating a few watermelon seeds would not provide a sufficient amount for these purposes.

Comparison: Citrulline in Watermelon Parts


Feature	Watermelon Seeds	Watermelon Flesh	Watermelon Rind
Citrulline Content (Fresh Weight)	Very Low (e.g., 0.03–0.1 mg/g)	High (e.g., 2.0–2.5 mg/g)	Moderate (e.g., 0.8–1.5 mg/g)
Citrulline Content (Dry Weight)	Low to Moderate	High to Very High	Highest
Nutritional Profile	Rich in protein, magnesium, iron, and fats.	Excellent source of water, vitamins B1, B6, C, and lycopene.	Contains high fiber, vitamins, and a significant amount of citrulline.
Best for Citrulline Intake	Not recommended as a primary source.	Good source of bioavailable citrulline, especially fresh.	Concentrated source, great for extracts or powder.

What are the benefits of eating watermelon seeds?

Even with low citrulline content, watermelon seeds are highly nutritious and shouldn't be discarded. When prepared correctly, they can be a great addition to your diet. Here's what they offer beyond citrulline:

Rich in protein: A good source of protein, which is essential for muscle growth and repair.
High in magnesium: Contains a significant amount of magnesium, a mineral vital for nerve and muscle function, and bone health.
Contains iron: Provides iron, a key component of hemoglobin that carries oxygen throughout the body.
Source of 'good' fats: Offers both monounsaturated and polyunsaturated fatty acids, which can be beneficial for heart health.

How to get the most from watermelon seeds

For the body to absorb the nutrients in watermelon seeds, they need to be prepared in a way that breaks down their tough outer shell. Simply chewing them raw means most of the nutrients will pass through undigested as insoluble fiber.

Here are some better ways to prepare them:

Roasting: Toasted watermelon seeds are nutty and can be seasoned with salt, chili powder, or cinnamon. Roasting them at 325°F (160°C) for about 15 minutes makes them a delicious snack.
Sprouting: Soaking mature, black watermelon seeds in water for a few days until they sprout can increase their nutrient bioavailability. These can then be added to smoothies or salads.
Grinding: Dry, immature seeds can be ground into a fine powder and used as a binder in recipes like veggie burgers or falafel.

Conclusion: More to seeds than citrulline

While it is a misconception that watermelon seeds are a concentrated source of citrulline, they are still a highly nutritious component of the fruit. The bulk of the fruit's citrulline is located in the flesh and especially the rind, which is often discarded. For those seeking citrulline's benefits, like improved blood flow and reduced muscle soreness, consuming the flesh and rind is more effective, or a higher dose from a supplement may be necessary. For those looking for a wholesome, high-protein snack, properly prepared watermelon seeds are an excellent choice. By understanding the different nutritional profiles of each part, you can ensure you're getting the maximum benefit from every bite of this versatile fruit.

Key takeaways

Low Citrulline: Watermelon seeds contain very low amounts of citrulline compared to the flesh and rind.
Rind is King: The highest concentration of citrulline is found in the white rind, particularly on a dry weight basis.
Seeds are Nutritious: When properly prepared, watermelon seeds are an excellent source of protein, magnesium, iron, and healthy fats.
Preparation is Key: To absorb the seeds' nutrients, you must roast, sprout, or grind them to break down the tough outer shell.
Citrulline Benefits: The citrulline in watermelon helps increase nitric oxide, which can support cardiovascular health and athletic performance.
Don't Discard the Rind: Considering its high citrulline content, the rind is a valuable, and often wasted, part of the watermelon.

Frequently Asked Questions

Watermelon flesh is a significantly better source of citrulline than the seeds. The concentration of citrulline in the flesh is much higher, and it is more readily absorbed by the body.

The amount of citrulline in watermelon seeds is very low. A study comparing different parts of the fruit found that watermelon seeds contained only 0.03–0.1 mg/g on a fresh weight basis, compared to 2.0–2.5 mg/g in the flesh.

Yes, watermelon seeds are healthy, especially when properly prepared. They are rich in protein, magnesium, iron, and beneficial fatty acids. However, eating them raw provides more fiber than readily absorbable nutrients.

While high heat can potentially affect some compounds, roasting primarily serves to improve the bioavailability of other nutrients like protein and minerals by breaking down the tough outer shell. Since the citrulline content in seeds is already very low, roasting is unlikely to have a significant impact on this specific amino acid for dietary purposes.

Yes, seedless watermelons contain citrulline. The amino acid is present in the flesh and rind, and studies show that the citrulline content can be comparable between seeded and seedless varieties.

The body converts citrulline into L-arginine, which then produces nitric oxide. This process helps to widen blood vessels, improve blood flow, and may aid in athletic performance by reducing muscle soreness.

For maximum nutrient absorption, roast the seeds with a little oil and salt, sprout them and add to salads or smoothies, or grind them into a powder for baking or as a binder. Chewing them raw is not an effective way to absorb the nutrients.