Threonine (T or Thr) is an amino acid, or a molecule that is one of the building blocks of proteins. It is an essential amino acid, meaning that it can’t be made by the body and therefore must be acquired through the diet. Many different foods contain threonine, including most meats, chicken, cottage cheese, mushrooms, and some leafy vegetables.
This amino acid supports many different body functions. Threonine is required for the formation of healthy bones and teeth and plays a role in the immune system because it is a necessary constituent of antibodies. It is also present in large amounts in muscle and connective tissues. It is thought to help contribute to their strength and elasticity due to its high proportion in collagen and elastin. Finally, it is required for the synthesis of certain neurotransmitters, suggesting a role in neural health.
It is well known that threonine is a necessary building block of many proteins, but its actual role in metabolism is not as well known. This amino acid can be converted to pyruvate or to alpha-ketobutyrate and eventually to succinyl-CoA, suggesting an association with the citric acid cycle. It is one of the amino acids that can be phosphorylated, which is a major mechanism by which cells control various signaling pathways. In addition, it is required for the body to synthesize two non-essential amino acids, glycine and serine, both of which play important roles in various physiological functions.
Due to the large amount of foods that contain this amino acid, threonine deficiency is considered rare in most westernized countries. Some vegetarians, vegans, or people with very restricted diets, however, may show slight deficiency of this amino acid. Symptoms of deficiency are usually psychological in nature, such as depression or excessive nervousness. Other symptoms may include digestive problems and, in severe cases, the build-up of fats in the liver, potentially leading to liver failure. People who suspect they have low threonine intake can safely supplement their diets by daily drinking a protein shake or eating a protein bar.
Some experiments have suggested that threonine may help to manage the symptoms of two diseases that affect muscle and nerve function: Lou Gehrig’s disease, or amyotrophic lateral sclerosis (ALS), and multiple sclerosis (MS). It may also help with mild depression. High levels of threonine can cause severe liver problems and possible ammonia toxicity in the body, so taking therapeutic doses of this amino acid is not recommended to anyone who is not under a doctor’s care.