L-glutamine acts as a major metabolic fuel for the small intestine. If the intestine loses its integrity (that is, its ability to absorb nutrients selectively) the bacteria present there may translocate. That means bacteria that normally provide a beneficial function when they reside in the intestine suddenly travel through the intestinal wall into the bloodstream and throughout the body, causing serious infection. L-glutamine prevents this from happening. That's why researchers in hospitals began supplementing some of their oral and tube-feeding formulas with this substance to keep the small intestines of seriously ill patients from breaking down.
What does this have to do with bodybuilding? Along with maintaining the intestines of patients, researchers found that L-glutamine also bolstered the immune system and regulated the rate of protein turnover in the muscle. Bodybuilding researchers quickly took note of this, and it wasn't long before protein powders and supplements were being fortified with L-glutamine.
There are additional benefits as well. From a recent study it appears that L-glutaminecan stimulate the release of growth hormone, results that were achieved with a relatively low dose of only two grams. That's great news for natural bodybuilders and maybe even greater news for men over 40, the age at which normal growth hormone levels start to decline.
The functions of growth hormone include accelerated protein synthesis and positive nitrogen balance. For bodybuilders this translates into muscle growth.
For men over the age of 40, whether or not they're bodybuilders, growth hormone can translate into improved health. One study found that some individuals over 40 release very little growth hormone during sleep, whereas growth hormone levels in children and young adults increase significantly during the first four hours of sleep. Since decreased levels of growth hormone are related to increased fat stores, decreased bone formation, decreased renal blood flow and decreased lean body mass, a natural method of increasing growth hormone to levels similar to those found in young adults would certainly provide health benefits.
The key is to take just enough glutamine to increase growth hormone to desirable levels. The more-is-better doctrine doesn't apply here. Taking larger amounts of L-Glutamine would be counterproductive, overloading your liver. The two grams used in the above-described study provided enough to raise serum glutamine levels without activating liver involvement, and the increase in growth hormone release that followed wasn't enough to cause liver stress but was enough to supply the benefits associated with growth hormone.
If you need another reason to take L-glutamine, consider that after ingesting it, the subjects' plasma bicarbonate levels increased. According to the researchers of this study, "The rise in plasma bicarbonate (and plasma glutamine) would be expected to drive up muscle cellular glutamine content, thereby slowing protein breakdown." This is because protein breakdown is accelerated under acidic conditions.
When should you take L-glutamine? The subjects in the study took it 45 minutes after a light breakfast. Eight of the nine subjects registered elevated blood glutamine levels at 30 and 60 minutes after ingestion. At 90 minutes after ingestion blood glutamine levels returned to normal, which was followed by an increase in circulating growth hormone levels and an elevation in blood bicarbonate levels.
Don't waste your money on unproven supplements. Try those that have proven effective in medical studies like L-glutamine.