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What does glutamine do? The cells of the immune system – like all the other cells in the body – need energy, and the fuels they use include glucose and glutamine. When a foreign organism is detected in the body, the cells of the immune system are sent to attack and inactivate it. The immune cells grow and divide rapidly, so the energy demand is high. Studies with isolated cells show that when they are stimulated to grow and divide in the test tube, this process is slowed if the supply of glutamine is inadequate. It has also been shown that hard exercise causes a fall in the concentration of glutamine in the blood plasma. There is not much doubt about this, and a reduction in the circulating glutamine concentration has been demonstrated during and after a variety of different types of exercise. From there it is an obvious step to suggest that hard exercise will restrict the ability of the immune cells to multiply and to attack invading germs because of the low plasma glutamine level. Low glutamine levels - much lower than those seen in the blood even after very hard exercise - have been show n to impair the capacity of these cells to multiply when stimulated in a test tube. Glutamine is sold to athletes as a training aid. This is based on four propositions: That athletes in hard training have an increased susceptibility to minor infections that interrupt training. That exercise causes plasma glutamine concentrations to fall. That immune function is impaired in these athletes because of reduced glutamine availability. That glutamine supplementation can enhance immune function and reduce the rate of illness. It is a small further step to suggest that taking glutamine supplements might help in preventing the fall in the glutamine concentration, and this might enhance the body's ability to resist infection. This last part of the argument seems logical, but it has not yet been shown that this can and does actually happen to athletes during hard training or after competition. Does it Work? Some parts of this story are established fact. Hard exercise does cause the glutamine level to fall, and glutamine supplementation can reduce or prevent that fall. The evidence that the reason that the immune system is less effective after hard exercise is due to a fall in glutamine is less good however, and there is little convincing evidence that glutamine supplementation reduces the rate of illness in athletes in hard training. At present, there is limited information on the influence of glutamine supplementation, and there is no clear pattern of results. Some studies by Professor Eric Newsholme and his colleagues at Oxford University suggest a beneficial effect of glutamine supplementation on resistance to infection after endurance exercise, but a positive effect was not always seen. Several other well controlled studies, however, have not seen any effect on the ability of the immune system to fight off infection, and the balance of the available evidence is not in favour of a beneficial effect of supplementation. Glutamine Supplementation and Immune Function: There is some evidence to support a role for glutamine supplementation in athletes BUT the evidence at present is not entirely convincing. Well controlled studies show that a high carbohydrate intake is a better strategy In spite of the attractiveness of this hypothesis, it has not yet been established that there is a clear link between hard exercise, compromised immune function and susceptibility to infection. Not all athletes in hard training experience problems, and, of course, most people, whether active or not, fall victim to a cold or flu at some stage. Nonetheless, glutamine supplementation for athletes is being promoted and supplements are on widespread sale in sports nutrition There are some other things that glutamine might do that could benefit the athlete. These will be discussed later.

Source: http://drinkfoodsocial.eu/pdfs/training/train09.pdf