L-Citrulline vs. L-Arginine: What's the Difference?

When it comes to elevating athletic performance, supporting nitric oxide production, and healthy cardiovascular function, L-citrulline and L-arginine are two popular amino acids people will consider for their purported benefits. Learning more about each and the key differences between them can help you decide which is the better choice based on your wellness goals.

What is L-Citrulline?

L-citrulline is a non-essential amino acid, which means the body can produce it naturally, though it can also be obtained through diet and supplementation. It plays an indirect role in the body’s production of nitric oxide, an important compound for cardiovascular health. L-citrulline is converted into L-arginine in the kidneys, which then supports the synthesis of nitric oxide. Unlike L-arginine, which is directly involved in nitric oxide production, L-citrulline acts as a precursor.

Natural Sources of L-Citrulline

L-citrulline is naturally found in several food sources, particularly fruits and vegetables. The most notable sources include:

Watermelon: Contains the highest natural concentration of L-citrulline
Cucumbers: Provide moderate levels of this amino acid
Pumpkins and Squashes: Offer smaller but notable amounts of L-citrulline
Bitter melons: Another vegetable source known for its L-citrulline content

Physiological Role of L-Citrulline

L-citrulline supports several important functions in the body, such as:

Nitric Oxide Production: L-citrulline converts to L-arginine in the kidneys, which then supports the body’s nitric oxide production. This process aids blood vessel dilation and contributes to healthy vascular function.
Urea Cycle: L-citrulline helps remove ammonia, a byproduct of protein metabolism, through the urea cycle. This detoxification process is important for metabolic balance.

L-Citrulline Benefits

L-citrulline is a popular supplement among athletes and fitness enthusiasts due to its role in various body functions. Its potential benefits include:

Blood Flow Support: L-citrulline contributes to nitric oxide production indirectly, which aids blood vessel dilation and supports circulation. This process allows oxygen and nutrients to reach muscle tissues during exercise.
Exercise Performance: Research suggests that L-citrulline may support endurance and power, potentially helping to reduce the feeling of muscle fatigue and lactic acid buildup during exercise.
Post-Workout Recovery: Some studies indicate that L-citrulline may support post-exercise recovery by reducing the sensation of delayed onset muscle soreness (DOMS). This potential effect could help athletes recover more quickly and maintain consistent training intensity.
Cardiovascular Function: L-citrulline’s role in nitric oxide production may support healthy cardiovascular function.
Potential Support for Erectile Dysfunction: Early studies are exploring L-citrulline’s potential effects on circulation-related functions, including support for blood flow in various areas of the body, including penile tissues.

What is L-Arginine?

L-arginine is a semi-essential amino acid that plays a direct role in the body’s production of nitric oxide, a compound involved in vasodilation and supporting cardiovascular function. While the body can synthesize some L-arginine on its own, additional amounts may be obtained through diet or supplementation, particularly during times of physical stress, such as illness, injury, or intense physical activity.

Natural Sources of L-Arginine

L-arginine is abundant in many protein-rich foods, including:

Red Meat: A primary dietary source of L-arginine
Fish and Poultry: Excellent sources of this amino acid.
Dairy Products: Milk, cheese, and yogurt offer moderate amounts of L-arginine.
Nuts and Seeds: Walnuts and almonds are particularly rich plant-based sources of L-arginine.
Legumes and Whole Grains: Foods like lentils, chickpeas, and oats provide additional L-arginine.

Physiological Role of L-Arginine

L-arginine supports several critical functions within the body:

Nitric Oxide Production: L-arginine is the direct precursor to nitric oxide, a molecule that’s involved in relaxing and dilating blood vessels. This vasodilation process may support circulation and healthy cardiovascular function.
Protein Synthesis: L-arginine is a building block for proteins, aiding in tissue repair and muscle growth, which can be beneficial for athletes and bodybuilders.
Hormone Secretion: L-arginine may influence the release of several hormones, including growth hormone and insulin, which are important for metabolic processes and overall bodily functions.

L-Arginine Benefits

L-arginine is often associated with several potential benefits that may support overall health and performance, including:

Athletic Performance: Some individuals consider L-arginine supplements for their potential to support healthy circulation and blood flow, which may assist in delivering oxygen to muscles during physical activity. This possible association has led to interest among athletes and fitness enthusiasts.
Cardiovascular Support: Due to its direct role in nitric oxide production, L-arginine is commonly used to support healthy cardiovascular function and circulation.
Wound Recovery: L-arginine is thought to play a role in collagen synthesis, which may be relevant for tissue repair and recovery processes. As such, it could be of interest to individuals recovering from injuries or surgeries.
Sexual Health: Some studies have investigated L-arginine’s potential effects on male sexual health, particularly concerning blood flow to reproductive tissues.

Comparing L-Citrulline vs. L-Arginine

When comparing L-citrulline and L-arginine, both are recognized for their roles in supporting nitric oxide production. However, they differ in absorption and utilization by the body.

Some research suggests that L-citrulline may be more effective at suporting blood levels of L-arginine compared to direct supplementation of L-arginine itself. This potential association has led to interest in L-citrulline as a potential option for supporting nitric oxide levels in the body. Still, L-arginine continues to be used for its direct role in nitric oxide synthesis.

Metabolic Roles

L-arginine

Semi-essential amino acid
Direct precursor to nitric oxide
Involved in protein synthesis and hormone secretion functions

L-citrulline

Non-essential amino acid
Converted to L-arginine in the kidneys
Involved in the urea cycle

Absorption and Bioavailability

L-citrulline has been shown to have an advantage over L-arginine in terms of absorption and bioavailability:

L-citrulline is noted as being efficiently absorbed by the intestines.
L-citrulline is less affected by liver metabolism.
L-arginine undergoes significant first-pass metabolism in the intestines and liver.

As a result, these characteristics may result in varying plasma levels of arginine when comparing L-citrulline supplementation to L-arginine supplementation.

Effects on Nitric Oxide Production

Both amino acids are involved in nitric oxide production, but through different pathways:

L-arginine is directly converted to nitric oxide by the enzyme nitric oxide synthase (NOS).
L-citrulline is first converted to L-arginine in the kidneys, which then produces nitric oxide.

Additionally, some studies suggest that L-citrulline supplementation may lead to sustained levels of L-arginine, which could influence nitric oxide production over time.

Exercise Performance and Recovery

L-citrulline has gained popularity in sports nutrition for its potential role in exercise performance and recovery:

Some research suggests that L-citrulline may support muscle recovery during physical activity.
L-citrulline supplementation has been associated with improved exercise performance.

Cardiovascular Health

Both amino acids are discussed for their potential roles in cardiovascular health:

Some studies suggest that L-arginine may be involved in promoting blood flow and supporting blood pressure levels.
L-citrulline is noted for its efficient conversion to arginine, which may influence vascular function and nitric oxide production over time.

	L-Citrulline	L-Arginine
Source	Found in fruits and vegetables like watermelon and cucumbers	Found in protein-rich foods like meat and dairy
Common Uses	Often associated with exercise performance and recovery support	Potential cardiovascular health and circulation support
Metabolism	Converted to L-arginine in the kidneys	Directly involved in the production of nitric oxide
Absorption	Believed to have higher bioavailability	Undergoes first-pass metabolism in the liver

Support A Healthy Lifestyle With Double Wood Supplements

At Double Wood Supplements, we offer high-quality L-Citrulline and L-Arginine products designed to support your fitness and health journey. Whether you're looking to enhance athletic performance, promote cardiovascular health, or support overall well-being, our supplements are formulated to meet high standards, helping you explore the potential benefits of adding these amino acids to your wellness routine.

Visit Double Wood Supplements to learn more about our offerings and see which supplements may be right fo your health and fitness goals.

[2] https://pubmed.ncbi.nlm.nih.gov/8764239/

[3] https://pubmed.ncbi.nlm.nih.gov/7543959/

[4] https://pubmed.ncbi.nlm.nih.gov/19128180/

[5] https://pubmed.ncbi.nlm.nih.gov/15817832/

[6] https://www.semanticscholar.org/paper/5c69dfbd4f19f4ef464241ef685d7b83de29854a

[7] https://pubmed.ncbi.nlm.nih.gov/9088044/

[8] https://www.semanticscholar.org/paper/9fbef46a29cf8e9db68785090c3bc923a7b2b2cc