What is Glutamine?
Glutamine is one of the 20 amino acids that make up proteins in our body. It is considered to be non-essential in the diet as it can be created from other amino acids. However, there are instances when it can be considered semi-essential. These include instances when people experience certain stresses, such as severe burns, surgery, cancer therapy and extreme exercise levels.
It is related to another amino acid called glutamate and the two can be easily interconverted. Note that the additive monosodium glutamate MSG, used in Chinese restaurants, that some people are reactive to, is related to glutamate and not glutamine.
About 90% of the glutamine that we don't get via the diet is produced in our muscles, where it is also stored1. Usage of glutamine however, is concentrated in the cells of our intestines, kidneys and parts of the brain along with cells of the immune system.
Amino acid or protein?
Some people state on principle that you don't need to supplement amino acids because protein provides all the amino acids that you need. This is basically rubbish, and two considerations can convince us of this. Firstly, the different amino acids have different affects on the body. An example is the amino acids, leucine and arginine, which can boost levels of insulin much more than any other amino acid. Secondly there is plenty of clinical evidence for the effective use of single amino acids in eliciting positive benefits for patients. Glutamine for instance, as is discussed below, is very effective at reducing the length of hospitalisation after surgery.
What does glutamine do?
Glutamine has a number of functions in our bodies:
- It helps keep our body from getting too acidic by allowing acid to be excreted in our urine.
- It provides energy for various cells such as those lining our gut, cells of the immune system and of the kidneys.
- It can boost recovery from intense exercise by boosting our stores of quick burning energy, glycogen.
- Glutamine has been used successfully on people with burns, reducing the chances of subsequent infections. It has also been used to help cancer patients being treated with chemotherapy and radiotherapy. It reduces the likelihood of gastrointestinal inflammation, as well as preventing some cardiac side effects of the cancer drugs.
- It has been suggested that glutamine supplementation may increase strength by promoting increased protein synthesis in the muscles.
- After conversion into glutamate by an enzyme called glutaminase, it helps transport the waste product, ammonia out of our body.
- After conversion into glutamate it can be used to create the anti-oxidant enzyme, glutathione, which reduces free radical activity in the body.
Benefits for the gastro-intestinal and immune systems.
For the above reasons glutamine supplementation has been associated with improvements in gastro-intestinal health, immunity and increased strength. From the gastro-intestinal angle it appears that oral glutamine can reduce intestinal permeability2. This is an important result as increased intestinal permeability can lead to problems with immunity, and as is seen with surgery and burns patients, recovery is normally significantly quicker when glutamine is taken.
Immunity is lowered in athletes who exercise for prolonged periods at a medium-high intensity. It has been suggested that because glutamine levels in the blood also fall after heavy exercise that the two facts could be related. However, the evidence for this is not that strong, and it seems likely that the immune cells can still thrive at the typical glutamine concentrations found after hard exercise in an otherwise healthy person3. Given that the number of white blood cells seems to remain static after glutamine supplementation, it would seem that a major benefit for immunity is only likely if you have undergone surgery, have burns, undergone cancer treatment or have serious overtraining syndrome.
Benefits for fast energy stores.
Endurance athletes in intense training have been found to recover more quickly after glutamine supplementation. This is due to an increase in the rate of glycogen storage after completion of exercise4. The evidence points to a 25% increase in the rate of glycogen synthesis after exercise if you add glutamine to a glucose type recovery mixture. This improvement may also be obtained using a combination carbohydrate-protein recovery drink also. However, the bottom line is that taking carbohydrate alone is probably not the best way to boost your glycogen stores immediately after exercise.
Many body builders use glutamine. The reason for this is that there is some evidence that glutamine can improve the hydration of our muscle fibres. It is transported into the fibres along with sodium (salt), and this increased concentration of salt draws water into the fibres by osmosis. A muscle fibre with more water in it is able to build itself up, whereas if it is dehydrated it tends to breakdown. However recent studies have not shown great anabolic effects from glutamine supplementation for healthy volunteers. It seems that the body can adjust to all but the lowest levels of blood glutamine, by creating glutamine from other amino acids when it needs it. However, for people on corticosteroids, people after surgery or with burns, there are likely to be benefits, as glutamine under these circumstances seems able to prevent muscle wasting away.
How do I boost my glutamine intake?
Glutamine is found as part of many proteins. There is plenty to be found in meat, fish, eggs and dairy. The average person probably absorbs between 5-10g of the amino acid glutamine from the gut every day. This glutamine will have come from protein which is broken down into amino acids in the stomach and small intestine. If you want a concentrated additional dose of glutamine it may be best to take a glutamine supplement. Given the amounts of glutamine available in the average diet, supplementation is probably only meaningful if you take 2g or more of glutamine per day.
The doses of supplemental glutamine vary. Most supplement manufacturers suggest taking at least 500mg per day to see any of the touted benefits. Others use a formula taking into account a person's bodyweight. So for instance 70g/kg bodyweight per day would imply that a 70kg male should take 4.9g per day. For short term usage (<14days) it appears that many people can take between 20-30g per day without any side effects3.
Glutamine supplements typically cost 10p for 5g. For most daily supplementation could be expected to cost somewhere between 10p and £1. Take it with other foods at room temperature. Glutamine has been used very successfully as part of total parenteral nutrition (TPN) formulas, where it is mixed with a whole load of other nutrients and amino acids. As such I see no need to take glutamine on its own, outside of meal times. Heat can destroy glutamine, so avoid having it with hot drinks or foods.
Do not take supplemental glutamine if you have kidney disease, liver disease, or Reye syndrome (a rare childhood disease involving swelling of the brain).
You get plenty of glutamine every time you eat protein containing foods. However there are times when it may be beneficial to take extra glutamine. One of these instances is when you are training hard. Studies have shown that glutamine can enhance the recovery of glycogen stores after exercise4. This should lead to later training sessions being more effective. What is clear in the context of intense training is that you can do much better than consuming carbohydrates on their own immediately after exercise. I would always advise that you consume some protein as well within the two hours after completing a heavy exercise session. Whether glutamine is needed to achieve optimal recovery is in my view open to more proof. It is clearly better than nothing, but consuming protein could be equally or more effectrive.