Creatine and glutamine are organic chemical compounds manufactured by the human body. Transported by blood and stored in muscle, creatine is synthesized from amino acids in the liver and kidneys and used to produce energy. Glutamine is one of 20 amino acids, specifically one of 11 non-essential amino acids that the body can manufacture on its own. It is synthesized mostly by the muscles, and is associated with anabolism, or tissue growth. Both creatine and glutamine are popular as supplements among athletes, particularly as bodybuilding supplements, though they function differently toward this end.
An acid found in skeletal muscle, creatine is a compound that is essential to metabolism, which is the sum of energy taken in through food minus energy expended through processes like movement, the digestion of food, and the maintenance of bodily functions. A non-essential nutrient, it is synthesized by the acids L-arginine, glycine, and L-methionine in the liver, kidneys, and pancreas.
Humans obtain some additional creatine from meats consumed in the diet, meat being the skeletal muscle of animals. Though both creatine and glutamine are found in muscle, only creatine is consumed here, as it is metabolized to produce adenosine triphosphate (ATP), the main compound fueling energy consumption in cells. Creatine also is linked to the retention of water in muscle cells, which supports protein synthesis in muscles while minimizing catabolism, or breakdown, of protein.
Glutamine is sometimes referred to as a conditionally essential amino acid, meaning that it may be essential in dietary or supplement form for certain individuals, such as those recovering from surgery, injury, or illness. As an amino acid, it is a substance required for protein synthesis, manufactured largely in muscle tissue and consumed mostly by intestinal cells, kidney cells, and immune cells. In the intestines, it is extracted through the cell walls and sent to the liver, where it may be converted along with glucose for cellular energy. It is metabolized in the kidneys to produce ammonium, which is necessary to maintaining the body’s acid-base balance. Additionally, glutamine is relevant to immune-system function in that it helps the body to recover from injury or illness by donating nitrogen for anabolic or tissue-building purposes.
It is in the latter function that creatine and glutamine are related. Glutamine’s tissue-building properties, as well as its supposed influence on human growth hormone (HGH) levels, make it a popular choice among athletes and bodybuilders as a supplement. It can also be obtained through foods in the diet like meats, fish, dairy, and eggs, as well as plant foods like spinach, beans, and beets.
Creatine has been linked to strength and energy increases, as creatine is converted in the muscles to creatine phosphate, a substance that increases the ATP in cells that muscles use for energy. These increases support creatine’s tissue-building properties in muscle. Both creatine and glutamine can be taken in oral supplement form by those wishing to build muscle, though about 50 percent of creatine in humans is supplied by animal foods, so it is recommended to consume plenty of animal protein as well.