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Citrulline is a non-essential amino acid, meaning the body can manufacture it on its own from glutamine and another amino acid, L-Aspartate, as well as the addition of some vital enzymes. Often we see it accompanying the amino acid arginine in pre-workout and nitric oxide supplements, but what exactly does citrulline do in the body?

Citrulline actually converts to arginine in the endothelial cells of the body, which are a thin layer of cells that line the interior surface of blood vessels. This conversion process is vital to nitric oxide production, which is a central role player in cardiovascular health.

When arginine is supplemented to produce nitric oxide, or for other purposes, most of it is utilized in the liver and kidneys, with only a small portion of it being used for NO production. The addition of citrulline to nitric oxide supplements acts to extend the life of NO, allowing for an increase and sustained production of nitric oxide for longer life and greater benefit. Some sources even indicate citrulline as a superior source of nitric oxide over arginine due to these facts.

In addition to superior nitric oxide production, citrulline helps promote an increase in energy levels, stimulates immune system function for overall health, wellness and well-being, and plays a vital role in the Urea Cycle, which is the conversion of ammonia into urea for waste.

While still not an extremely popular supplement, the amino acid citrulline does exhibit many positive factors. With its list of benefits and powerful nitric oxide production, we may see citrulline start to take over arginine as the forerunner for pre-workout supplement ingredients.