Glutamine, or L-glutamine, is an amino acid derived from another amino acid, glutamic acid. Glutamine plays a role in the health of the immune system, digestive tract, and muscle cells, as well as other bodily functions. It appears to serve as a fuel for the cells that line the intestines. Heavy exercise, infection, surgery, and trauma can deplete the body's glutamine reserves, particularly in muscle cells.

The fact that glutamine does so many good things in the body has led people to try glutamine supplements as a treatment for various conditions, including preventing the infections that often follow endurance exercise, reducing symptoms of overtraining syndrome, improving nutrition in critical illness, alleviating allergies, and treating digestive problems.

There is no daily requirement for glutamine because the body can make its own supply. As mentioned earlier, various severe stresses may result in a temporary glutamine deficiency.

High-protein foods such as meat, fish, beans, and dairy products are excellent sources of glutamine. Typical daily intake from food ranges from approximately 1 to 6 g.