Glutamine

Main functions

• Increases immune function.
• Prevents overtraining syndrome.

[1], [2], [3], [4], [5], [6], [7]

Theoretical basis

Glutamine is the most abundant amino acid that is contained in the human plasma and muscles. Skeletal muscles synthesize, accumulate and release glutamine at high speed. It participates in the synthesis of proteins, the donor of nitrogen for the synthesis of nucleotides, carries nitrogen transport between different tissues, is a substrate for the formation of urine. Glutamine - a powerful source of nutrition for intestinal enterocytes and cells of the immune system.

Glutamine, apparently, can be conditionally indispensable during a high metabolic stress or critical states. The levels of skeletal and plasma glutamine are reduced in infections, operations, injuries, acidosis and burns. Long-term endurance loads, such as a marathon, can also reduce the concentration of glutamine in the plasma. Moreover, the concentration of glutamine in plasma is much lower in overtrained athletes than in athletes in the control group.

Since glutamine is indispensable for the optimal functioning of the immune system, a reduced plasma concentration in it can worsen the immune function and increase the risk of infection. Glutamine supplements can enhance immune function, reduce the risk of infection and help prevent overtraining syndrome.

Research results

The use of glutamine supplements for inpatients during periods of severe physiological stress is well known. Oral or parenteral glutamine supplements after major injuries or surgeries help maintain muscle glutamine concentration, improve the excretion of 3-methylhistidine (a muscle catabolism marker), prevent intestinal atrophy, increase body weight and reduce hospital stay.

However, the benefits of glutamine supplements for athletes during periods of intense training are not yet established. Castell et al. Studied the effect of glutamine supplements on runners on average, marathon and super marathon distances, as well as on elite rowers. Observations were conducted during training sessions and competitions. Immediately after the load to exhaustion, 72 athletes were given a drink containing glutamine, and 79 - a placebo. Athletes filled out questionnaires about the occurrence of infections within seven days after the load. The number of athletes reporting no infection was significantly higher in the glutamine supplement group (81%) than in the placebo group (49%). Cases of infection were least noted among runners at medium distances and most of all in marathoners and super marathoners, as well as in elite rowers after intensive training. In a later experiment, Castell et al. Reported that the glutamine supplement did not seem to affect the function of the immune system (estimated by the distribution of lymphocytes).

Rohde et al. The effect of glutamine supplements and repeated loading on the state of immunocompetent cells in an arbitrary cross-placebo-controlled experiment was studied. Eight athletes cycled 30, 45 and 60 minutes at 75% V02max and rested for 2 hours between the races. Although plasma glutamine levels were maintained in the group consuming a glutamine supplement and were reduced in the placebo group, the number of lymphocytes and lymphocytes stimulated by phytohemagglutinin decreased 2 hours after each arrival in both groups. Thus, postnagruzochnye immune changes do not depend on reduced concentrations of glutamine in the plasma.

Recommendations

The concentration of glutamine in the plasma can decrease after intensive training, which leads to the depletion of glutamine. However, an adequate daily intake of carbohydrates can help prevent the depletion of muscle glycogen and overtraining, as well as maintain the normal status of glutamine. While some preliminary data show that glutamine supplements can reduce respiratory infections in athletes, further research is needed to confirm the findings.