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Sulphurous amino acids – why they are indispensable

Amino acids differ in their chemical structure. Perhaps you have heard of sulfur-containing amino acids. Methionine and cysteine have sulphur in their chemical composition.

We will introduce these two sulphur-containing protein building blocks to you in more detail here and go into their functions in our body.

Sulphurous amino acids & their special features

The so-called proteinogenic amino acids are the building material of every body tissue. They are also known as protein or protein building blocks. The building blocks form chains of varying lengths. From these we build up the body’s own proteins and peptides.

The human organism can form some of these building blocks itself. Others have to be taken up again and again with food. For this reason, proteinogenic aminos are divided into two different main groups. One group comprises the essential, the other the non-essential building blocks.

Chemical structure

In terms of their chemical structure, aminos consist of a main chain and several side chains. The structure of the side chains differs slightly for each amino acid.

These differences give rise to different subcategories, according to which the building blocks can be further subdivided. Among these categories is one that contains sulfur in the side chain. In the chemical nomenclature, the S appears in the chemical structure of two building blocks. This characteristic applies to the non-essential amino acid cysteine and the essential methionine.

A special mineral substance

Sulphur compounds are found in almost all living organisms. Even in the human body, where the mineral makes up on average 0.25% in all body tissues. In total, the total sulphur content in the human organism can amount to about 0.6%.

The mineral is considered indispensable for various cell functions. Among other things, it contributes to the stabilisation of certain protein structures. It is also a component of some enzymes. The latter perform catalyst functions in our body. This means that they promote or even make possible reactions between various other substances. In doing so, they act like a kind of ignition spark that sets off a biochemical reaction.


The sulphurous, essential amino acid must be taken in with the diet. The requirement for methionine can vary from person to person. On average, values between 13 mg and 16 mg/kilogram body mass are assumed. Under certain conditions, this requirement is said to increase to up to 21 mg/kilogram bodyweight.

Methionine is contained in the following foods, for example:

  • beef
  • poultry meat
  • nuts
  • sesame
  • salmon
  • soybeans

Among other things, methionine plays a role in the formation of L-carnitine. L-carnitine is a substance in the human body that plays a decisive role in energy metabolism in human cells. The substance transports fatty acids to the mitochondria, the power stations in our cells. Furthermore, cysteine is also formed from methionine. This is the second protein building block, which has a sulphur building block in the side chain.

Methionin gehört zu den schwefelhaltigen Aminosäuren

Further functions of methionine

Methionine has other tasks and functions:

The protein building block is a precursor of taurine. This non-proteinogenic protein building block protects, among other things, our heart health.

It is also involved in the formation of glutathione. This is a substance that has an antioxidant effect. Antioxidative substances combat so-called free radicals. These are reactive and aggressive oxygen particles that can damage cells. Vitamin C, vitamin E, the mineral selenium and various other substances are also antioxidants. Methionine also has a function in selenium metabolism.

Furthermore, methionine supports

  • liver function and health by reducing excessive fat deposits.
  • the regeneration of the kidneys.
  • detoxification of heavy metal bodies such as lead.

Methionine in medical use

Urinary acidification can be achieved by the intake of larger amounts of methionine. This effect occurs when excess methionine forms sulphuric acid. This is the case, for example, with cystitis that is treated with antibiotics. Methionine can help to inhibit bacterial growth by acidifying the urine.

As a cat owner, you can also find methionine in pet food. Cats often suffer from diseases of the urinary and kidney tract. Acidification of the urine is also useful here.


The second and non-essential sulphurous amino acid is cysteine. This protein building block is produced by our organism itself with methionine and homocysteine. It is also contained in various foods, such as

  • salmon
  • chicken eggs
  • poultry meat
  • pork
  • sunflower seeds.

The sulphur-containing cysteine is an essential component of various fibre proteins, which are summarised under the name keratin. Cysteine is, therefore, the basis of skin, hair and nails. Similar to methionine, cysteine is involved in the formation of various other important substances including

  • Glutathione
  • Taurine
  • Coenzyme A.

Required values isolated from methionine are usually not given for cysteine. However, cysteine is often considered together with methionine because both protein building blocks contain sulphur compounds and have overlapping functions.

Schwefelhaltige Aminosäuren chemische Struktur

Cysteine in medical application

Cysteine is used to make some pharmaceutical substances that you may know as NAC or ACC.

These substances are said to be able to liquefy viscous mucus in various bronchial and pulmonary diseases. Cysteine is also used to prevent radiation damage and in some neurological diseases. Newborns, premature babies and people suffering from cirrhosis of the liver do not have a certain enzyme that is responsible for the formation of cysteine. Here, under certain circumstances, as with an essential amino acid, cysteine must be constantly supplied from outside.

What is homocysteine?

You may have heard of homocysteine in connection with the health of your blood vessels. Now you may wonder if cysteine and homocysteine are related.

Homocysteine is also a protein building block, but it does not belong to the group of proteinogenic building blocks. This means that homocysteine does not contribute to tissue formation.

Instead, this protein building block plays a part in the body’s own formation of cysteine.

Homocysteine participates in conversion processes of protein building blocks and other substances in the human body. However, elevated homocysteine levels are associated with various diseases.

According to modern scientific findings, the so-called calcification of the blood vessels is significantly related to increased homocysteine levels. Similar connections are also discussed with various dementia diseases. Among other things, a vitamin B12 deficiency is thought to contribute to the presence of too much homocysteine.

Sulphur compounds in protein building blocks are indispensable

Sulphurous amino acids have a special place in the group of proteinogenic building blocks.

Our organism needs these amino acids not only for the formation of tissue, for example, skin, hair and nails. They are also important for liver health and in the fight against oxidative substances.

The importance of sulphurous amino acids can therefore hardly be overestimated. Since they are the precursors of various antioxidants, you may be able to benefit from these two amino acids, especially in old age. Oxidative processes are also increasingly associated with ageing. However, the need for research on this topic is still high.

Maik Thies (Fitnessfachwirt IHK)

Unser Ernährungsexperte Maik Thies arbeitet seit 2011 erfolgreich als Personalcoach und Manager für Fitness- & Freizeitanlagen im Gesundheitsmarkt.

Als Fitnessfachwirt und Weltmeister im Bodybuilding gibt er sein Wissen an Menschen weiter, die körperliche und mentale Grenzen neu definieren möchten und Wert auf gesunde und ausgewogene Ernährung legen. Zu seinen Kunden zählen u.a. Skeleton Atlethen Janine Becker und Alexander Gassner, Bobpilotin Stephanie Schneider, Rallye Motorsportler Sepp Wiegand etc.

Er unterstützt amino4u dabei, die Prozesse des Körpers für Sie einfach und verständlich zu erklären und Ihnen dadurch die Möglichkeit zu geben, wieder mehr Gesundheit und Lebensfreude zu erlangen.

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