Glutamine is
the most abundant amino acid in the body – comprising approximately half
of the free amino acids in the blood and muscle. As a non-essential amino
acid, glutamine can be produced in the body by conversion from another
amino acid - glutamic acid (primarily by the skeletal muscle and liver.
Glutamine’s main functions in the body include serving as a precursor in
the synthesis of other amino acids and glucose for energy. Cells of the
immune system, the small intestine and the kidney are the major consumers
of glutamine.
Claims
Boosts immune system
function
Maintains muscle mass
Prevents muscle
catabolism (breakdown)
Enhances glycogen
storage
Aids recovery from
exercise
Theory
Intense
exercise training results in a well-described drop in plasma glutamine
levels. Chronically low glutamine levels have been implicated as a
possible contributing factor in athletic overtraining syndrome as well as
the transient immunosuppression and increased risk of infections that
typically affects competitive athletes during intense training and
competition. Under conditions of metabolic stress, the body’s need for
glutamine may exceed its ability to produce adequate levels – meaning
that a dietary source is required to prevent catabolism of skeletal muscle
– the primary source of stored glutamine in the body.
Scientific
Support
A significant
body of scientific literature exists to support the beneficial effects of
glutamine supplementation in maintaining muscle mass and immune system
function in critically ill patients and in those recovering from extensive
burns and major surgery. When plasma glutamine levels fall, skeletal
muscles may enter a state of catabolism in which muscle protein is
degraded to provide free glutamine for the rest of the body. Since
skeletal muscle is the major source of glutamine (other than the diet),
prolonged deficits in plasma glutamine can lead to a significant loss of
skeletal muscle protein and muscle mass. Very little specific work has
been done, however, to address the primary target population for the
majority of commercially produced glutamine supplements on the market
today – competitive athletes
In recent years, at least a half-dozen studies have been conducted on
glutamine supplementation in athletes and a strong basis exists for the
efficacy of glutamine supplements in athletic populations. For example,
glutamine’s role in immune system support has been shown to prevent
infections following intense bouts of physical activity – which tend to
reduce plasma glutamine levels. Glutamine supplements have also been shown
to play a role in counteracting the catabolic (muscle-wasting) effects of
stress hormones such as cortisol, which are typically elevated by
strenuous exercise. The function of glutamine in stimulating glycogen
synthase, the enzyme which controls the synthesis and storage of glycogen
fuel storage in muscles and liver, may provide a mechanism by which
glutamine supplements promote enhanced fuel stores. Glutamine supplements
cause a rapid rise in cellular glutamine levels and glutamine stores in
muscle. Glutamine is also thought to increase cell volume, where it may
stimulate the activity of enzymes in the liver and muscles involved in
glycogen storage as well as those involved in anabolic activities such as
protein synthesis. Glutamine supplements have also been hypothesized to
increase levels of growth hormone, which may be expected to help stimulate
protein synthesis and encourage gains in muscle mass and strength, but
reliable evidence for this effect of glutamine supplements has not been
demonstrated by clinical studies.
Safety
Glutamine
supplements are well tolerated at levels up to at least 20 grams per day
and intakes of as much as 40 grams per day should induce no significant
adverse effects outside of mild gastrointestinal discomfort. As with any
isolated amino acid supplement, consumption in divided 2-4 divided doses
throughout the day should increase total body stores without posing
significant absorption issues.
Value
Glutamine
supplements are relatively inexpensive compared to other amino acid
supplements. For anybody exposed to heightened levels of stress, such as
those recovering from injury, surgery, or intense exercise, glutamine
supplements represent an economical way to promote tissue repair, reduce
muscle catabolism and help prevent infections.
Dosage
For the
immune system support and anti-catabolic actions that are of interest to
most athletes, recommended doses range from 1-10 grams.
References
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Glutamine Info & Review
