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Threonine

Threonine is an essential amino acid with lipotropic properties that the body cannot produce itself and must therefore be obtained from the diet. Threonine was isolated from the protein fibrin in 1935 and synthesized in the same year. This amino acid is often added to animal feed to improve the protein profile of breeding animals. Glycine is a non-essential amino acid with a sweet taste that was isolated from gelatin in 1820. Glycine is the simplest amino acid (without d- and l-forms) and is considered less reactive when incorporated into proteins and enzymes. In its free state, it is involved in a number of important processes in the body. Glycine can be formed from threonine and serine as well as from other sources. Serine is also a non-essential amino acid; it was isolated from sericin, a silk protein, in 1865. Serine can be formed from threonine and glycine as well as from glucose.

Threonine, glycine and serine have important functions in the body

Many of the functions of threonine have not yet been researched in detail. It is generally required for growth, uric acid metabolism and the immune system. Threonine is an important building block in the protein metabolism chain and contributes to the formation of enzymes and hormones. It is involved in the biosynthesis of vitamin B12 and isoleucine and in turn requires vitamin B6, magnesium and niacin for its functions. Threonine can strengthen the immune system and is required for the formation of immunoglobulins and antibodies. It helps to maintain the health of the thymus gland, in which the T lymphocytes that are important for the immune system mature. Threonine can be used to generate energy during strenuous physical activity. Together with glycine and serine, threonine plays an important role in the metabolism of porphyrin.

Glycine is needed for the biosynthesis of nucleic acids, bile acids, creatine phosphate and other amino acids. It promotes the excretion of uric acid and can lower uric acid levels in the blood. Glycine is required for the synthesis of heme, an important component of haemoglobin. The same applies to the formation of purines (part of the genetic material) and glutathione (a coenzyme). Glycine is also part of the fluid in the prostate and is thought to contribute to its healthy function. Glycine can inhibit or weaken the signals of neurotransmitters in the central nervous system, thus having a calming effect. Glycine dampens the activity of hyperactive nerves and improves neuromuscular control. Serine is a component of phospholipids present in biological membranes. It contributes to the formation of neurotransmitters and DNA. Serine is needed to build choline, acetylcholine, cysteine and tryptophan and is part of many enzymes.

The main suppliers of threonine, glycine and serine

Threonine is abundant in dairy products, egg yolk, meat, rice, potatoes and pulses. Cereals contain relatively little threonine. Glycine is present in almost all protein-containing foods, especially in fish, meat, beans and dairy products. About 3 to 5 grams are ingested daily with food. Serine is mainly found in gluten, soybeans and peanuts.

Typical groups for an additional requirement of threonine and/or glycine

  • Threonine possibly for high physical performance
  • Glycine possibly for benign prostatic hyperplasia (BPH)
  • Threonine or glycine possibly in hyperactive nerve reactions and neuromuscular disorders

When threonine, glycine and serine are missing in the body

A lack of threonine leads to rapid fatigue, low energy, loss of appetite and weight loss. A deficiency of glycine and serine is usually rare, as both amino acids can be formed from threonine and other substances and converted into each other. An imbalance between the amino acids serine and cysteine is considered characteristic of some psychoses.

Can you overdose on threonine, glycine and serine or are there side effects?

Threonine and glycine are not known to have any toxic effects. Glycine should not be taken in high doses without a doctor's recommendation if you have kidney or liver disease. The same applies to the intake of medication; interactions may occur. Excess serine can contribute to psychotic processes and increase blood pressure.

The daily requirement of threonine

The daily requirement for threonine in adults is around 14 mg per kg of body weight.