What is threonine?

Find out more about essential amino acids

Threonine is an essential amino acid. It is important for regulating protein balance in the body. This amino acid is a precursor to serine and glycine. These are two other amino acids necessary for muscle tissue production. L-threonine has many uses in the body. It supports:

  • Digestive function
  • Immune system
  • Liver function
  • Muscles and connective tissues
  • Central nervous system.

Health benefits

Effects on the digestive system

L-threonine and digestionA large portion of l-threonine is absorbed in the upper reaches of the small intestine (ileum). Here this amino acid protects the digestive tract. Threonine is needed to produce the mucus gel layer that covers the digestive tract. This mucus is a barrier to digestive enzymes that can damage the intestines. Threonine is also used in other endogenous secretions. Hence, this amino acid is important for supporting healthy gut function.

Animal studies involving chickens, pigs, and rats have found that a low threonine diet leads to digestive problems and a reduction in immune function1 2 3. Scientists believe this is due to a decline in the gut mucus barrier. Not only does this negatively affect the immune system, but it also disrupts nutrient absorption. Therefore this can lead to a cascade of health problems.

Supporting the immune system

L-threonine also helps to produce antibodies to boost the immune system. The thymus gland is responsible for making T lymphocytes (T- cells).  These cells fight off infections, and the thymus uses threonine to make T-cells. Ensuring that the body has enough threonine to support immune function is important to safeguard against a host of diseases.

Liver health benefits

Threonine works together with the amino acids methionine and aspartic acid to support the liver. These amino acids help to facilitate lipotropic function. In this process the body digests fats. Therefore in the absence of sufficient threonine the liver would become overwhelmed by fats. In the worst case scenario, this would result in liver failure.

Supporting bones, muscles and connective tissues

The structural proteins collagen and elastin need threonine. This amino acid is the precursor for serine and glycine. Therefore these two amino acids are necessary to create these proteins. Collagen is the most abundant structural protein in the body. It is vital for connective tissue formation and maintenance.

Thus, threonine helps to support strong and elastic muscles and connective tissue throughout the body. This includes the heart, which is why threonine is important for good cardiovascular health. Furthermore, this amino acid can help to accelerate healing of wounds and bones following injury.

Cognitive function

L-threonine and cognitive functionThreonine is in high concentrations in the central nervous system. There has been interest in the use of this amino acid in the treatment of Amyotrophic Lateral Sclerosis (Lou Gherigs Disease)4, 5. However, further studies are needed.

Additionally, other research has indicated the potential of threonine to help reduce some of the symptoms of Multiple Sclerosis (MS), including a reduction in spasticity6. Furthermore studies have found that threonine can help to fight depression and improve mental health7, 8.

Symptoms of threonine deficiency

Common symptoms of  threonine deficiency include digestive difficulties, emotional agitation, confusion and a fatty liver. This amino acid is usually abundant in a balanced diet. Consequently, deficiencies are rare. However, vegans and strict vegetarians may want to consider a supplement. This is because meat and dairy products contain the highest concentrations of threonine. This amino acid is also available in protein bars/powders and amino acid capsules/tablets.

Dietary sources of threonine

Some of the highest concentrations of this essential amino acid are found in fish, meat, dairy, eggs, carrots, and bananas. Nuts, beans, seeds and other vegetables also contain threonine but in lower concentrations. Adults need approximately 15mg of this amino acid per kilogram of body weight daily for optimal functioning9.


In summary, threonine is an important essential amino acid. It has a range of roles in the human body. It helps to support the immune system and healthy digestion. This amino acid is also essential for tissue development and maintenance. Therefore, it plays a key role in heart and liver health. In addition, the central nervous system also requires adequate concentrations of this amino acid. This helps to support cognitive function.

Most people acquire healthy levels of threonine through their diet. In cases where a deficiency is identified supplements may be required. However, it is important to only take threonine supplementation under the guidance of a medical practitioner as too much can be dangerous and cause liver damage and ammonia toxicity.


  1. Azzam M, et al. (2011). Effect of supplemental L-threonine on mucin 2 gene expression and intestine mucosal immune and digestive enzymes activities of laying hens in environments with high temperature and humidity. Poultry Science. Volume 90, Issue 10 (pp. 2251-2256).
  2. Hamard A, et al. (2010). A moderate threonine deficiency affects gene expression profile, paracellular permeability and glucose absorption capacity in the ileum of piglets. Journal of Nutritional Biochemistry. Volume 21, Issue 10, (pp. 914-921).
  3. Faure M, et al. (2005).  Dietary threonine restriction specifically reduces intestinal mucin synthesis in rats. Journal of Nutrition. Volume 135, Issue 3, (pp.486–91).
  4. Blin, O et al. (1992). A double-blind placebo-controlled trial of L-threonine in amyotrophic lateral sclerosis. Journal of Neurology. Volume 239, Issue 2, (pp. 79-81).
  5. Tandan, R et al. (1996). A controlled trial of amino acid therapy in amyotropic lateral sclerosis: I. Clinical, functional and maximum isometric torque data. Neurology. Volume 47, Issue 5, (pp. 1220-6).
  6. Hauser, S et al. (1992). An antispasticity effect of threonine in multiple sclerosis. Archives in Neurology. Volume 49, Issue 9, (pp. 923-6).
  7. Chalexka-Franaszek, E. and Chuang DM. (1999). Lithium activates the serine/threonine kinase Akt-1 and suppresses glutamate-induced inhibition of Akt-1 activity in neurons. Proceedings of the National Academy of Sciences of the United States of America. Volume 96, issue 15, (pp. 8745-60)
  8. Beaulieu, J. (2011). A role for Akt and glycogen synthase kinase-3 as integrators of dopamine and serotonin neurotransmission in mental health. Journal of Psychiatry & Neuroscience. Volume 37, Issue 1, (pp.7-16).
  9. Sudhir B, et al. (2002). Threonine requirement of healthy adults, derived with a 24-h indicator amino acid balance technique. American Journal of Clinical Nutrition. Volume 75, Issue 4, (pp.698-704).