Glutamine has been considered as a “bodybuilding staple” for many years and is often mentioned in the same breath as other proven supplements such as whey protein, creatine and fish oils.
Although I don’t expect to convince those who have been using glutamine for years and swear by its effects, in this post I’ll be providing an evidence-based review of why l-glutamine supplements are almost certainly a waste of money for the average person trying to build muscle and burn fat.
What Is Glutamine?
As you probably already know, protein is made up of smaller individual building blocks called amino acids. Glutamine is the most abundant amino acid in the body and actually makes up about 2/3 of those found in muscle tissue.
Glutamine is a non-essential amino acid (meaning the body can produce it on its own) which becomes “conditionally essential” under periods of particularly high stress when the need for glutamine may exceed its availability.
Supplement companies sell isolated l-glutamine products in pill and powder form and promote it as having a wide variety of uses for those following a muscle building or fat burning program.
The Benefits of Glutamine
Studies have shown that supplementation with the amino acid L-glutamine can minimize breakdown of muscle and improve protein metabolism. Glutamine is the most common amino acid found in your muscles – in fact, over 61% of your skeletal muscle is glutamine. Glutamine consists of 19% nitrogen, making it the primary transporter of nitrogen into your muscle cells.
During intense training, glutamine levels are greatly depleted in your body, which decreases strength, stamina and recovery. It can literally take up to six days for levels of this amino acid to return to normal – a fact that most people who train are grossly unaware of. Glutamine also plays a key role in protein synthesis and studies have shown that supplementation can minimize the breakdown of muscle and improve protein metabolism.
Glutamine also increases your ability to secrete human growth hormone (HGH), which helps metabolize body fat and support new muscle growth. So in turn, glutamine’s anti-catabolism ability prevents the breakdown of your muscles. This is extremely useful for bodybuilders during the cutting phase before a contest, as well as for individuals trying to get rid of some extra body fat to look good during the summer months without losing any muscle.
Why Does Your Body Need Glutamine?
To fully understand why glutamine is beneficial to the body we must all endure a little Biochemistry lesson. The body uses glutamine to shuttle ammonia around in the body, so blood levels of glutamine try to maintain constant. Glutamine is craved by the digestive tract and the immune system as a fuel. Most bodybuilders eat more than enough protein from the supermarket, but they do not get enough glutamine through the digestion of meats and other proteins.
The muscles cells are the giant storehouses of glutamine. Under certain pathological circumstances the body's tissues need more glutamine than the overall amount supplied by diet and natural synthesis such as during a bodybuilder's strenuous workout[5,24].
During catabolic stress, for instance, intracellular glutamine levels can drop more than 50 percent, and plasma concentration can fall by 30 percent. It is under these circumstances that supplemental glutamine becomes necessary[23].
Skeletal muscle contains the greatest intracellular concentration of glutamine, comprising up to 60 percent of total body glutamine stores, and is considered the primary storage depot of glutamine, and thus the primary exporter of glutamine to other tissues [1]. In times of metabolic stress, glutamine is released into circulation, where it is transported to the tissue in need. Intracellular skeletal muscle glutamine concentration is affected by various assaults including injury, sepsis, prolonged stress, and starvation. Besides skeletal muscle, the lungs are the next largest producer of glutamine[9,12].
Glutamine is especially useful postworkout when nutrients are at a low until recovery. In this condition research shows glutamine levels are significantly reduced, taking up to one month to return to baseline[4]. In athletes, glutamine has been used as a marker to indicate overtraining. This fall in glutamine is catabolic to muscle tissue. BCAA's [comprising 37% of total muscle] are debranched from skeletal muscle, and the resulting molecules are used to synthesis glutamine.
In the catabolic state, glutamine is the first amino acid used to correct that deficiency. Glutamine drives protein into the muscle cell where it is synthesized for growth[6,8]. This means that additional Glutamine is necessary during periods of stress [such as intense weight training which induces a catabolic state which has been shown to uniformly decrease Glutamine levels by 50%, taking several hours to return to normal levels[1]. Additionally, L-Glutamine also decreases protein degradation [BCAA catabolism], resulting in bigger, stronger muscle cells[23].