This article was featured in Muscular Development Magazine, November 1996.
To most people, glutamine is just one of the 20 amino acids that
are used to make protein. It's not even considered to be an
essential amino because the body is capable for making it for
itself. However, glutamine may be the single most important amino
acid in the body for creating anabolic conditions in the muscle
and protecting us from the ravages of overtraining.
It seems almost unbelievable that a single, free amino acid could
accomplish so many things in the body. The importance of glutamine is underscored by its sheer abundance. Although every bodily
tissue contains glutamine, many human tissues contain very high
levels, and it is the most abundant amino acid in muscle and
plasma. When something is normally found in large amounts in the
body, it is an important function, especially in those tissues
that contain the most. The question is, what happens when our
bodies are put under stress and these levels of glutamine start
to fall? This is exactly what is being asked about the effects of
exercise, which can quickly reduce the levels of glutamine in the
muscles and plasma.
Glutamine is considered to be a nonessential amino acid because
it is made by the body and is not absolutely required to be obtained through the diet. Although we do get glutamine in our diets, it is necessary for the body to produce more to meet the vast amounts required.
The major tissue in the body for producing glutamine is muscle. Muscle is capable of combining ammonia and the amino acid glutamate to form glutamine. The production of glutamine in the muscle is so great that it accounts for more than 60% of the free amino
acid pool in muscle cells. These large muscle stores also account
for most of the body's glutamine reserves, and they can release
glutamine into the circulation to maintain plasma levels and
provide other tissues with glutamine.
The Effects of Stress on
Under normal physiological circumstances the body can produce all
the glutamine that it needs. A delicate balance is maintained
between tissues that produce and release glutamine and those that
depend on it. The reason so many tissues need glutamine is that
is had so many functions in the body. It regulates ammonium
levels in the tissues, which can be toxic to the body's cells.
The ammonium is used to produce glutamine for release into the
blood. Here, glutamine is transferred to other tissues to be used
for fuel, especially the cells of the immune system. Glutamine is
directly involved in the regulation of protein synthesis and
breakdown and is a powerful anabolic stimulus. For these reasons,
glutamine is perhaps one of the most versatile amino acids in the
When the body's physiology is altered by factors, such as stress
or disease, its demands for extra glutamine can change drastically. One form of stress that occurs to the body is when a person
bodybuild using heavy poundages and intense training. During this
training the use of glutamine by other organs of the body increases in response to bodily stress. As a result, plasma gluta
mine levels begin to plummet drastically. To replenish these
levels, the muscles start to release their glutamine stores into
Intense exercise also cause the production of lactic acid and
ammonium by the muscles. To deal with these toxic products, the
production of glutamine from glutamate and ammonia is also
increased. this extra glutamine is rapidly transported into the
blood to such a degree that plasma glutamine levels begin to rise
within five minutes of exercise. As a result, the many tissues
that need glutamine, but can't produce it, are provided with
ample supplies during the exercise induced stress. The problem is
that the muscles are having their intracellular stores depleted
in the process.
Intense exercise also cause the release of catabolic hormones,
such as corticosteroids. These glucocorticoids also contribute to
the depletion of muscle glutamine stores by increasing the release of glutamine from muscle cells. These catabolic steroids
can cause glutamine to continue to be release from muscle even
after exercise has stopped and the body no longer needs extra
supplies. The result is that muscle become severely glutamine
Glutamine - the Anabolic
Glutamine is known to promote anabolic conditions in muscle cells
and increase the rate of protein synthesis. It was long thought
that glutamine was directly responsible for this anabolic state,
but it no seems that glutamine indirectly promotes growth by
increasing the hydration state of muscle cells.
The amount of water in cells can change in a matter of minutes,
going from being fully hydrated to a state of dehydration. It has
been found that the amount of water inside a cell can alter its
metabolism, especially protein synthesis and turnover. When cells
are swollen with water, this inhibits the breakdown of protein,
glycogen and glucose. It also stimulates protein and glycogen
synthesis. If a cell becomes dehydrated, it shrinks and immediately goes into a carbolic state that breaks down the muscle's
Experiments have shown that if isolated muscle cells are placed
in a solution that contains insulin and amino acids, the insulin
drivers the amino acids into the muscle cells and protein synthesis is increase. Protein synthesis can also be increased by
placing the cells in pure water, which causes them to swell.
Interestingly, when placed in a salt solution, this quickly draws
water out of the cells and they rapidly enter a catabolic state.
Thus, it appears that cell swelling is necessary for maintaining
an anabolic state.
When glutamine levels are high in the muscle cells, this
stimulates the entry of other amino acids into the cell. Amino
acids cannot directly enter into the muscle cell, but must be
carried in by a special transport system. The unique thing about
this transport system is that when it allows am amino acid to
enter, it also allows sodium to enter A the amino acid and sodium
levels increase inside the muscle, this excess sodium causes
water to be absorbed across the membrane and the cell swells to
an anabolic state.
When glutamine levels are depleted during exercise, this reverses
the transport of amino acids and sodium. The cells become dehydrated and enter a catabolic state.
The Role of Glutamine in
Men and women who are serious athletes and bodybuilder walk a
fine line between being undertrained and overtrained.
Overtraining results when increasing volumes and intensity of
training become out of balance with recovery time. Once a person
crosses over the line and sets foot in the overtraining zone,
from there on out all their hard work and effort will only send
their performance spiraling downward. The harder they work, the
less their gains.
One reason a person experiences the overtraining syndrome is that
they may deplete their bodies of glutamine to the point that they
can't recover. As explained above, an intense exercise cycle can
deplete the muscles of glutamine. Studies have shown that after
such a session, glutamine levels in the muscles bottomed out
between 4 to 6 hours post-exercise and took more than 24 hours to
fully recover to pre-exercise levels.
It is easy to see that if a person trains intensely each day that
they will start depleting their muscles glutamine stores before
they have fully recovered from the workout. The result is that
each day the amount of muscle glutamine gets a little lower.
Eventually, the muscle go below the critical amount of glutamine
needed to sustain a anabolic state and they revert into a long
term catabolic state. The more a person works out to try and
makes their muscles grow, the more glutamine they use and the
greater the catabolic response. Some athletes have suffered from
the overtraining syndrome for over two years and have been shown
to have low plasma glutamine levels for the entire time. This may
be due damage to the muscle's glutamine synthesizing system as a
result of it being overtaxed from too much training.
Individuals suffering from overtraining also are more
susceptible to disease and infections as a result of lowered
immunity. This may be due to the role of glutamine as a primary
source of fuel for the cells of the immune system, particularly
lymphocytes, macrophages and killer cells. In addition, glutamine
is used as precursor in the synthesis of nucleic acids, which are
necessary for cell division.
It is thought that adequate amounts of metabolic intermediates
for building key molecules are needed to allow a rapid response
when immune cells are faced with a challenge. During periods of
immunological assaults, glutamine metabolism is increased to
support the rapid cell division, protein synthesis and the production of antibodies and cytokines. These immune cells rely on the plasma to supple them with adequate supplies of glutamine. If these supplies are not met by the plasma, which is ultimately
provided by the muscles, the immune cells cannot mobilize to
defend the body against an infection of disease. Thus, low glutamine levels severely impair the immune system.
Don't Forget the
Because intense exercise can severely deplete the muscles of
glutamine and the overtraining syndrome may be the result from
the progressive and prolonged loss of glutamine, it is imperative
to conserve the muscle's glutamine stores. Previously it has been
suggested that glutamine was broken down to glutamate in the
stomach and that oral supplementation was of no benefit. Now
reports show that oral glutamine is a safe and effective means of
providing supplemental free glutamine to the body. Oral glutamine
has been shown to reduce the loss of glutamine from muscles and
help them maintain their reserves during a variety of catabolic
For this reasons, it makes sense to take a glutamine supplement that provides the free from of this amino prior to intense exercise. This will raise plasma glutamine levels and prevent the depletion of muscle glutamine stores. After exercise, a high quality protein carbohydrate supplement should be taken within 30 minutes to aid in recovery. The protein will provide amino acids, especially glutamine, and the carbohydrate will boost insulin levels, which will help transport these amino acids to the muscle.
As the amino acids are transported into muscle, they will also
promote water uptake to keep the muscles hydrated. This superhydrated state will prevent the muscles from entering into a catabolic state and promote anabolic growth. Because glutamine stores are not depleted, recovery time will be shorted and there is less
chance that one will become the victim of the overtraining syndrome due to progressive loss of glutamine stores.
Glutamine may be considered to be a nonessential amino acid for
the normal individual because the body has the ability to make
it, this there is not a great a need to acquire it in the diet.
However, for the elite centurions of the bodybuilding community
who use iron to forge a better body, glutamine can be considered
to be a "conditionally essential" amino acid. It is conditional
essential because intense weight training pushes the body to use
glutamine in such vast amounts that it cannot be produced fast
enough and thus causes temporary and eventually long term deficiencies.
Therefore, keep in mind that glutamine is one of the most important amino acids in the body and may be the single most important amino acid supplement for the bodybuilder.