Nutrition Diet: What Fruit Has the Highest Citrulline?

In the world of functional foods, watermelon stands out as the most significant natural plant source of L-citrulline, an amino acid with notable cardiovascular and performance-enhancing properties. This non-protein amino acid is efficiently converted in the body to L-arginine, boosting nitric oxide production and improving blood flow. Understanding what fruit has the highest citrulline can be a key part of an optimized nutrition diet.

Quick Summary

Watermelon is the top fruit source of citrulline, a compound that enhances nitric oxide production and blood circulation. Its content varies by part and cultivar, with the rind often containing more per dry weight than the flesh. Other cucurbits also provide citrulline, but in much lower quantities.

Key Points

• Watermelon is the richest fruit source of citrulline: The amino acid was named after the fruit (Citrullus lanatus), highlighting its high concentration in watermelon.

• The rind contains high citrulline levels: Watermelon rind, often discarded, has a higher concentration of citrulline per dry weight than the flesh.

• Citrulline boosts nitric oxide: In the body, citrulline is converted to L-arginine, which increases nitric oxide production, leading to improved blood flow.

• Benefits include lower blood pressure and exercise performance: Increased nitric oxide from citrulline helps relax blood vessels, potentially lowering blood pressure and enhancing athletic performance.

• Other cucurbits contain citrulline: While watermelon is superior, other foods like cucumbers, pumpkins, and melons contain smaller amounts of citrulline.

• Supplements offer a targeted dose: For specific health or performance goals, citrulline supplements provide a high, concentrated dose, which may be more effective than food sources alone.

Watermelon: The Undisputed King of Citrulline

Watermelon, scientifically known as Citrullus lanatus, is definitively the richest fruit source of the amino acid L-citrulline. The name 'citrulline' itself is derived from the Latin word for watermelon, a testament to its abundance in the fruit.

Research has consistently shown that watermelon contains significantly higher concentrations of citrulline compared to other fruits in its family, such as squash, melon, and cucumber. The citrulline content varies depending on the specific cultivar, with 'Crimson Sweet' and 'Dixielee' watermelons noted for their high concentrations. Interestingly, studies have shown that the concentration of citrulline is not uniform across the fruit.

The Surprising Truth About Watermelon Rind

While most people only eat the sweet pink flesh, the often-discarded rind contains even more citrulline on a dry weight basis. The rind is an underutilized source of this beneficial amino acid and can be juiced, pickled, or blended into smoothies to increase dietary intake.

Citrulline Content by Watermelon Part (Based on Dry Weight)

• Rind: Higher citrulline content than flesh on a dry weight basis.
• Flesh: While having a lower concentration than the rind on a dry weight basis, the sheer volume of flesh consumed means it is still a major source of citrulline for most people.
• Seeds: Some studies have noted citrulline in the seeds, but the amount is typically much lower than in the flesh or rind.

How Citrulline Benefits Your Body

Once consumed, citrulline is converted into another amino acid, L-arginine, which then increases the production of nitric oxide (NO). Nitric oxide is a potent vasodilator, meaning it helps relax and widen blood vessels. This effect has several health implications:

• Improved Blood Flow: By promoting vasodilation, citrulline can help improve circulation throughout the body.
• Lowered Blood Pressure: Several studies have linked citrulline supplementation to a reduction in both systolic and diastolic blood pressure, particularly in individuals with prehypertension or hypertension.
• Enhanced Exercise Performance: The increased blood flow to muscles can improve exercise performance, reduce muscle soreness, and boost oxygen delivery during exercise.
• Cardiovascular Health: By supporting healthy blood pressure and blood vessel function, citrulline contributes to overall cardiovascular wellness.

Beyond Watermelon: Other Citrulline Sources

While watermelon is the richest source, other foods contain smaller amounts of citrulline. These are often other members of the Cucurbitaceae family.

Notable examples include:

• Cucumbers: Part of the same family as watermelons, cucumbers also contain citrulline.
• Pumpkin: Another cucurbit, pumpkin provides some citrulline, though far less than watermelon.
• Squash: Both summer and winter squash varieties contain citrulline.
• Melons: Certain melons, like cantaloupe and casaba, contain citrulline.
• Bitter Melon: This vegetable contains citrulline, primarily in its arils (seed coverings).

Choosing Your Citrulline Source: Food vs. Supplements

There are two main ways to increase your citrulline intake: consuming whole foods or taking supplements. Both have their pros and cons, which are important to consider for your nutrition diet.

Feature	Watermelon (Food Source)	L-Citrulline Supplements
Primary Form	L-citrulline in a whole food matrix	Isolated L-citrulline or citrulline malate powder/capsules
Concentration	Varies significantly depending on cultivar and part (flesh vs. rind)	High, standardized dose (often 1.5-6 g per serving)
Bioavailability	Good; the natural food matrix may enhance absorption compared to synthetic citrulline.	High; bypasses first-pass metabolism, leading to a greater and more consistent increase in plasma arginine.
Nutrient Synergy	Contains other beneficial nutrients like lycopene, vitamins A and C, and hydration.	Lacks the vitamins, minerals, and antioxidants found in whole foods.
Practicality	Requires consuming large volumes to reach high therapeutic doses.	Convenient for achieving specific high doses needed for some health benefits or athletic performance.
Cost	Generally affordable, but large daily quantities can be costly.	Varies, but often more expensive than purchasing the fruit.

Maximizing Your Citrulline Intake Through Diet

For a balanced approach, prioritize whole food sources of citrulline, especially watermelon, while considering supplements for targeted needs. Here are some tips:

1. Eat the Whole Fruit: Don't discard the rind. While the flavor is different, it can be juiced with the flesh, pickled, or blended into smoothies to maximize your citrulline intake.
2. Choose the Right Type: For potentially higher concentrations, consider different cultivars. Orange- and yellow-fleshed watermelons may contain more citrulline than red-fleshed varieties on a dry weight basis.
3. Explore Other Cucurbits: Include cucumbers, pumpkins, and squash in your meals for a cumulative effect of citrulline and other nutrients.
4. Juice It Up: Watermelon juice provides an easily digestible form of citrulline. Unpasteurized juice may offer higher bioavailability.
5. Consider Supplements for Performance: If you're an athlete looking for specific performance enhancements, a supplement might be more effective for achieving the necessary high doses. Always consult a healthcare provider first.

Conclusion

In the grand scheme of nutrition, few fruits compare to watermelon when it comes to citrulline content. For those looking to naturally boost nitric oxide and improve cardiovascular health, adding more watermelon—and potentially its rind—to your diet is a flavorful and effective strategy. While other cucurbits offer trace amounts, the sheer quantity and bioavailability in watermelon make it the superior choice. Whether enjoyed fresh or as a concentrated juice, watermelon is an excellent addition to any nutrition diet focused on circulation and overall well-being. For specific therapeutic benefits, supplements provide a concentrated option, but should be discussed with a healthcare professional.

Frequently Asked Questions

Which specific watermelon cultivar has the most citrulline?

Studies have identified cultivars like 'Crimson Sweet' and 'Dixielee' watermelons as having particularly high citrulline levels, but the exact amount can vary based on growing conditions.

Can I get enough citrulline from food instead of supplements?

Yes, it is possible to get beneficial amounts of citrulline from food, especially watermelon. However, to achieve the high doses sometimes studied for therapeutic effects or athletic performance, a supplement may be necessary.

How should I consume watermelon rind to get more citrulline?

Watermelon rind can be juiced with the flesh, pickled, or blended into smoothies. Some people also chop and add it to salads or stir-fries.

Does cooking watermelon affect its citrulline content?

While the effects are not fully conclusive, some food processing methods, particularly thermal treatments like pasteurization, have been shown to reduce citrulline content in watermelon juice.

Are yellow or red watermelons higher in citrulline?

Research suggests that yellow or orange-fleshed watermelons may have slightly higher citrulline content than red-fleshed varieties on a dry weight basis, though the differences can be minor.

What are the health benefits of citrulline?

Citrulline helps increase nitric oxide, which improves blood flow, may lower blood pressure, and enhance exercise performance by delivering oxygen to muscles more efficiently.

Are there any side effects to taking citrulline supplements?

L-citrulline is generally well-tolerated. High doses may cause stomach discomfort or heartburn in some individuals. It's important to consult a doctor, especially if you are on blood pressure medication.