MaximalCrazy
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From a quick Google search:Can’t we just take l-arinine? @Helen
Citrulline bypasses the liver, unlike arginine, and is not subject to breakdown by arginase. Therefore, using citrulline in place of arginine allows for higher arginine levels and higher NO production. One study found that over 80% of L-citrulline is converted to arginine in the blood vessels.
Of course, citrulline is an even better NO booster than arginine. This has been shown in a couple of studies. The first one found that subjects taking equivalent doses of citrulline and arginine had higher arginine blood levels when they took citrulline versus arginine. A later study from German researchers reported that it took just half the amount of citrulline as arginine to raise blood concentrations of arginine to an equivalent level. The German researchers also found that a 3-gram dose of citrulline produced the highest increase in arginine and NO levels.
The greater effectiveness of citrulline versus arginine appears to be due to excessive breakdown of arginine in the body after it's consumed. This is due to the enzyme arginase that resides mainly in the intestines and liver. In fact, one study suggested that the amount of arginine consumed from oral supplements that was utilized in NO production was less than 1% of that consumed. Citrulline bypasses the liver, unlike arginine, and is not subject to breakdown by arginase. Therefore, using citrulline in place of arginine allows for higher arginine levels and higher NO production.
One study found that over 80% of L-citrulline is converted to arginine in the blood vessels. And yet another study in professional cyclists showed that those supplementing with citrulline had a significant increase in NO production during exercise.
In addition to boosting NO levels, using citrulline to increase arginine levels in the body can also elevate growth hormone (GH) levels. This works through arginine's ability to inhibit growth hormone inhibiting hormone (GHIH)—or somatostatin—which normally inhibits GH production. By inhibiting GHIH, arginine increases the production and release of GH from the anterior pituitary gland, which leads to higher blood levels of GH.