L-arginine and L-citrulline are both amino acids with potential therapeutic applications. L-citrulline, once in the body, is converted to L-arginine.

As a result, L-citrulline can be supplemented to increase L-arginine levels. Since L-citrulline is a precursor of L-arginine, it can also be used to treat the same conditions as L-arginine.

Both L-arginine and L-citrulline are nitric oxide boosters that are commonly used in many popular preworkout supplements.

What is Arginine?

L-arginine is primarily responsible for increasing nitric oxide levels. High levels of nitric dioxide relaxes and dilates blood vessels, increasing blood flow to many organs including the heart, skin, and sexual organs.

L-arginine, a conditionally necessary amino acid, is something the body can usually make. However, stress and injury can reduce the body’s ability to produce enough.

L-arginine can be found in many foods including meats, milk products, poultry, nuts, and chocolate. According to New York University Langone Medical Center, the recommended daily intake is between 2 and 8 grams. However, higher doses can be used to treat certain conditions.

Benefits of Arginine

L-arginine is able to treat and prevent many conditions. Most commonly, L-arginine supplements are used for its blood-vessel-dilating effects, which can be effective in improving a number of heart-related conditions.

According to MedlinePlus, L-arginine has been used to treat high blood pressure, chest pain, and coronary heart disease. L-arginine can also be used to treat male infertility or erectile dysfunction.

L-arginine is good for health because it can improve circulation and stimulate growth hormone release.

What is Citrulline?

L-citrulline, which is an essential amino acid, can be synthesized by the body from other nutrients. L-citrulline can be made from glutamine, an amino acid.

Citrulline supplements are promoted for certain purposes, including enhancing athletic performance. Citrulline is usually consumed in the form citrulline malate, which can be taken between 6 and 18 grams daily.

Benefits of Citrulline

NYU Langone Medical Center points out that supplement companies market L-citrulline (a supplement that improves oxygen performance) as complimentary with creatine, which is a supplement designed to increase anaerobic exercise performance. However, there is no scientific evidence to support the claim that L-citrulline can increase aerobic exercise.

L-citrulline might still be useful for exercise in certain capacities. Examine.com rates L-citrulline as a “C”, meaning that it has been rated single-blind, twice-blind, or multiple-cohort studies support L-citrulline’s ability to increase protein synthesis (muscle build), reduce muscle soreness, fatigue, enhance immunity, and increase growth hormone and nitric oxide blood levels.