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If you're regularly involved in strenuous exercise or are concerned about your cardiovascular health, you might find a supplement called L-citrulline malate of potential value. Citrulline is an amino acid that's considered nonessential because your body makes a sufficient supply and dietary intake isn't essential. Modern research suggests that L-citrulline malate, the chemical form of citrulline available as a supplement, can boost energy and may help lower your risk of certain chronic problems.

Citrulline Metabolism

You can obtain citrulline from food or your body can manufacture it from ornithine, another amino acid you obtain from food, through a biochemical process called the urea cycle. This cycle helps rid your body of ammonia, a waste product of protein digestion. After your digestive system metabolizes citrulline malate into citrulline, enzymes in your liver cells convert it into another amino acid called arginine, and other enzymes then convert arginine into nitric oxide in a process that also produces new citrulline molecules. Nitric oxide is a vasodilator that can help protect you from cardiovascular problems by lowering blood pressure and improving blood flow to your organs, according to experts at the University of Southern California. Although your body can make cirtulline in this way, research suggests that consuming extra citrulline may have significant health benefits.

Enhanced Exercise Tolerance

Research on the body's usage of citrulline during exercise suggests that consuming a citrulline supplement might enhance performance. A study published in 2011 in the "Journal of Nutritional Science and Vitaminology" reported that laboratory animals fed citrulline and subjected to intense exercise were able to perform longer and also had lower levels of blood ammonia and lactate, two waste compounds produced during exercise, than a placebo group. In a small clinical study published in the September 2010 issue of the "European Journal of Applied Physiology," researchers found that male cyclists who took citrulline two hours before exercise had blood markers indicating improved use of amino acids by their tissues, compared to a control group. These promising results are preliminary, however, and still need confirmation in larger clinical trials.

Cardiovascular Benefits

Several clinical studies suggest that supplementation with L-citrulline malate may improve the health of your arteries and heart. For example, a study published in "Caridology Journal" in 2010 that involved subjects with heart failure found that consumption of L-citrulline for two months helped improve performance on a treadmill and also resulted in lower blood pressure and better heart function. Another study published in the March 2012 issue of the "International Journal of Cardiology" found that healthy male subjects who consumed L-citrulline for seven days had improved arterial function because arterial walls were less stiff, compared to a placebo group. These are positive findings, but both studies were small, and larger clinical trials are still needed to confirm citrulline's cardiovascular benefit.

Citrulline Sources

L-citrulline malate supplements are available as pills from health food stores and some pharmacies. Because citrulline is a natural amino acid, it's generally considered safe and without significant side effects. No minimum effective dose has been established, but clinical studies used a daily dose of 5 to 8 grams. Talk to your doctor about L-citrulline malate to decide if the supplement might be helpful for you.