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Glutamine Supplementation and Overtraining

It is common to see supplement manufactures making unrealistic claims when promoting their products, trying to impress us with a few links referring to some recent research papers to support their statements. A good example is glutamine targeted at the weight lifting and bodybuilding community to help them build more muscle.

Glutamine happens to be the most abundant free amino acid in our body, comprising 40% of muscle amino acid content and 20% in the plasma. The basic hypothesis promoted by the supplement manufacturers is simple. Glutamine encourages building of protein (anabolism) and inhibits breakdown of protein (catabolism). Exercise depletes glutamine stores in muscle, thus having a negative effect on recovery and growth whereas our dietary intake of glutamine is limited to 5-8g per day. In order to prevent this depletion we should use glutamine supplements.

But one important fact supplement manufacturers won’t tell you is that our bodies produce about 80g of glutamine a day. This amount is sufficient to meet all normal physiological requirements. And while glutamine levels can deplete under stress, if this occurs when weight training, you must be doing something wrong. Glutamine depletion is actually being recognised as one of the markers of overtraining, which is something weight lifters and bodybuilders should be seeking to avoid. Exercise of the intensity and duration needed to deplete glutamine stores in muscles is associated with increased release of catabolic hormones and inhibition of growth hormone release. This is the exact opposite of what athletes should be trying to achieve. However, in exercise of moderate intensity, especially where the workload is being progressively increased (like in weight-lifting), the body’s glutamine levels are known to improve.

In order to further increase muscle glutamine levels you should better be consuming branched chained amino acids and glucose. This stimulates skeletal glutamine synthesis and promotes anabolic recovery. Studies show that when carbohydrates with protein containing branched chained amino acids are consumed, the addition of extra glutamine is unnecessary, as it has no impact on performance, recovery or growth.

Is Glutamine Supplementation Good for Anyone?

Situations of severe metabolic stress and trauma, such as surgery, cancer, burns or injury, generate increased demands upon body’s glutamine stores that are in excess of what our body can synthesise. Glutamine is also the fodder for the immune system and its depletion causes immunosuppression. Long periods of inactivity such as bed rest can also trigger a decline in the production of glutamine and its eventual depletion.

Glutamine depletion (means in excess of what the body is able to produce) commonly happens in exhaustive exercises. That is why many endurance athletes have an increased incidence of infections of the upper respiratory tract such as colds, coughs, sinus infections or sore throats, which are due to immunosuppression associated with glutamine depletion. However, glutamine supplementation can help against these infections. After just one week of supplementation with 5 grams of glutamine twice daily, a noticeable decline in infection rate of marathon runners was observed.

It is not defined which duration and intensity of exercise is so demanding as to require glutamine supplementation. It is clear, though, that for a one hour weigh training session, with rests in between sets, the effect is zero. However, for marathon runners the advantages are quite convincing as they are simply overtraining and create enormous stress on their body. For cases in between, such as football, rugby, basketball, tennis etc., this is where it gets unclear. Supplementation will likely improve recovery and can be recommended for periods of intense training and competitive activity. In those who are recovering from injuries and unable to train, glutamine supplementation could prevent decrease in synthesis that accompanies long periods of rest.

The body’s biggest consumer of glutamine is our gut, using it as fuel. The demand is so big that circa 50% of the amount we consume will be absorbed by the gut cells and will not reach the systemic circulation. In a hospital glutamine is infused in order to avoid gut utilisation. Nonetheless, oral supplementation can still make sense with glutamine metabolism by the gut being associated with improving intestinal health. This amino acid is known to protect the integrity of the gut lining, suppress inflammation and protect against diarrhoea.