L-arginine and L-citrulline

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In the body, the arginine-nitric oxide pathway is utilized to convert arginine into nitric oxide with help from the enzyme nitric oxide synthase (NOS).

Increasing nitric oxide levels relax the blood vessels, allowing them to widen or dilate, and dilated blood vessels deliver more blood flow to tissues like muscle fibers.

Nitric Oxide

Nitric oxide or just NO is a relatively simple molecule, which has huge ramifications in the human body and is featured heavily in the study of neurosciences, physiology, and immunology.

It is such an important molecule that it was once named molecule of the year by the famous journal ‘Science’.

Nitric oxides function in the human body, acting as a neurotransmitter and plays a role in immunity. It is also most commonly known for its ability to relax the smooth muscle around blood vessels in order to dilate them.

This helps to increase blood flow including peripheral blood flow to working skeletal muscles.

This has been proposed to help with increased muscle growth and prolonged endurance.

In order to produce the majority of nitric oxide in the body, arginine reacts with oxygen, a molecule called NADPH and the enzyme nitric oxide synthase to produce citrulline and nitric oxide.


Arginine is an amino acid that is considered conditionally essential, or semi-essential, depending on one’s health and development status. Thus, Arginine may or may not need to be supplemented by outside sources.

For instance, pre-term infants lack the ability to produce arginine internally and so require an external source of arginine.

Arginine is found in abundance in most meats, seafood as well as in high quantities in nuts and seeds, and can also be produced in the body from reactions involving other amino acids such as glutamine and citrulline.

L-Arginine benefits include the ability to help the body produce and synthesize proteins, which are essential in the process of muscular repair and growth.

It is also a constituent in the formation of bones and tendons, and helps stimulates the production of growth hormones, natural sterols, which help the muscles rebuild and enlarge after an intense workout.

L-Arginine improves immune function, speed up the healing time of injuries, and also helps remove cortisol, which controls stress levels, and other waste products in the body.


L-citrulline comes from the Latin word Citrullus, which means watermelon.

It is a non-protein amino acid. This means that it is not a necessary amino acid to act as a building block for protein.

Citrulline is an amino acid that is closely related to arginine, and can be derived internally through two reactions; as part of the urea cycle or through the nitric oxide synthase reaction.

New research has begun looking at citrulline as a way of providing endogenous arginine due to its ability to escape being metabolized by our digestive system.

Citrulline can be converted to arginine with the help of two enzymes, namely, argininosuccinate synthetase (ASS) and argininosuccinate lyase (ASL).

L-citrulline is used for heart disease, bodybuilding, increasing energy, and improving athletic performance.

It is also used against fatigue, muscle weakness, sickle cell disease, erectile dysfunction, high blood pressure, and diabetes.

L-citrulline other benefits include its ability to help reduce body fat levels, and in maintaining natural energy production, ATP (adenosine triphosphate), which can often drop off drastically during a hard workout.

A 2010 study showed Citrulline malate enhances athletic anaerobic performance and relieves muscle soreness.

L-Arginine vs. L-Citrulline

L-arginine and L-citrulline supplements are combined in muscle building formulas to support protein metabolism and maintain muscle tissue.

Both supplements are non-essential amino acids, however, it seems that less L-citrulline is needed by the body, and as much as 80% of the supplement is converted to L-arginine in the blood vessels.

L-arginine and L-citrulline supplements are used to increase nitric oxide (NO) levels in the blood, promoting positive effects for muscle growth, energy, stamina, and strength, especially, for bodybuilders.

German researchers found that a 3 g dose of L-citrulline produced the highest increase in L-arginine and nitric oxide levels because the process of breaking down L-citrulline by-passes the liver.

L-Arginine and L-citrulline are nitric-oxide boosting substances.

Both supplements support the elimination of oxidative stress in the arteries and ease clogging.

However, research suggests that L-citrulline may be more effective at a lower dosage, than L-arginine.


L-arginine and L-citrulline should not be taken with blood pressure medication.

Neither should it be taken with a low blood pressure condition.

They should also not be taken with Nitrates medications, insulin, and cholesterol-lowering agents, and should be avoided for people with kidney and or liver impairments.

Viagra may also interact with this supplement, and herpes virus conditions and Asthma symptoms can be made worse.

Make sure to consult your doctor before using these supplements, or any other.

Best Selling L-Arginine Supplements

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