L-cysteine 2018-02-14T13:24:02+00:00
amino acids are important for a healthy and happy life without illnesses and diseases

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L-cysteine is a proteinogenic amino acid contributing to building protein and includes the element sulphur.

It can be synthesised in the human liver and is therefore not an essential amino acid.
It should be however, be supplemented in order to cover the required daily amounts.
This amino acid is only included to a small degree in proteins (2 %).

This makes a varied diet very important to avoid Cysteine undersupply.

L-cysteine is built directly from the essential amino acid L-methionine.

This makes the abundance of L-methioning in the body a critical factor to the body’s supply of L-cysteine.

It is therefore sometimes counted as a semi-essential amino acid and also due to its role as a catalyst in many important metabolic cycles.

Benefits of L-cysteine

Cysteine is able to fulfill several important functions in the human body due to its specific structure including sulfur and contributes significantly to the general well-being.

Especially when the individual has chronic conditions, cataract or arthritis he or she will greatly benefit from the appropriate supplementation of this semi-essential amino acid.

Also illnesses of the intestines usually increase the needs for L-cysteine, because many nutrients simply cannot be absorbed and get lost as a result of the digestive system being  compromised.

Environmental factors such as stress or extreme physical strain will also lead to an increased demand in Cysteine.

The effect of extreme Reduction Diets on the body is not to be underestimated. This can severely deplete the body’s levels of vitamins and amino acids.
L-cysteine is very soluble in water. When cooking the above foods, special care should be taken that they are not be kept in water for too long to avoid washing out the amino acid.

L-cysteine and Anti-Aging

Beautiful muscular man after bath

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L-cysteine supports the synthesis of the highly antioxidative Glutathione and can also be stored in this chemical form. It therefore plays an important part in detoxification and the resulting protection of several tissues and organs.
According to recent research studies this does not only slow down the natural process of ageing, but also helps in preventing dementia and multiple sclerosis, because both conditions are associated with an accumulation of toxins.

Boosting the immune system

Glutathione also inhibits inflammation and leads to an overall strengthening of the immune system. It also stimulates the productions of so-called Leukotrien, which supports the defensive work of the macrophages, which are key elements in the immune system.
In cases of short falls of Cysteine infections may therefore become more prevalent due to the reduced amount of killer cells. In extreme cases, however, such shortfall can lead to cancer when the immune system is extremely weakened.
L-cysteine is also important in the metabolism of lipids. It plays, for example, a part in building essential fatty acids and therefore enables the production of cell membranes and protective covers of nerve endings. These consist mainly of myelin, a dielectric (electrically insulating) material that forms a layer, the myelin sheath, usually around only the axon of a neuron.
This protects the axon from environmental damage and attacks from free oxidative radicals. In this way L-cysteine has very high preventative potency in helping to prevent major degenerative illnesses such as Parkinson.

Healthy Skin and Hair with L-cysteine

A very important role of the semi-essential amino acids lies with protein synthesis, meaning the building of proteins. L-cysteine is a natural building block of many important structural proteins in the connective tissue. The body is also able to convert this multifunctional nutrient into Taurine, which is important for the conducting of electric nervous impulses, the digestive as well as the vascular system.

L-cysteine increases male fertility

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Supplementation with l-cysteine in the form of NAC has been shown to lower the concentration of damaging reactive oxygen species within semen, which increases sperm motility (the ability to swim forward and in a straight line). In a study by Ciftci and colleagues the effects of NAC supplementation were assessed on 120 men diagnosed with idiopathic infertility1.

Sixty men were given 600 mg/day orally of NAC for three months, while another 60 men received a placebo. Men who received NAC showed significant improvements in semen volume, viscosity, and sperm motility.

The total antioxidant capacity also improved and a reduction in destructive reactive oxygen species declined. The ability of NAC supplementation to improve sperm count and motility increases the potential for fertilisation. Enhancing semen viscosity is also important because this makes it easier for the sperm to propel forward towards the egg.

Other studies have shown that NAC together with the trace element selenium is beneficial for male reproductive health. Safarinejad and Safarinejad explored the effects of selenium and NAC on 468 infertile men diagnosed with idiopathic oligo-asthenoteratospermia2.

Subjects were randomly assigned to either a placebo, 200 microg selenium orally daily, 600 mg N-acetyl-cysteine orally daily, or 600 mg N-acetyl-cysteine plus 200 microg selenium daily over a period 26 weeks.

All semen parameters were significantly enhanced following the combination therapy. Sperm concentration increases, sperm motility improved, and the percentage of sperm with normal morphology also increased.

How to take L-Cysteine to improve male fertility

Specifically for male fertility, it is most efficient and affordable to take a combination supplement with several proven male fertility micro-nutrients. These will positively affect sperm count, motility and morphology simultaneously.

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L-cysteine reduces inflammation

L-cysteine can help reduce inflammation of reproductive tissues and organs. If the prostate or seminal vesicles are suffering from inflammation, fertility levels decline. The anti-oxidant effects of NAC and associated glutathione can help to alleviate inflammation, which improves fertility.

L-cysteine combats Illnesses

immune system response

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L-cysteine exceptionally strong antioxidant properties have so many positive effects on the overall health, that it can be used for both prevention as well as therapy of illnesses.
A study in 2009 investigated the anti-inflammatory properties of L-cysteine.  It was already well-known that there was a direct correlation between oxidative stress und inflammatory processes. The assumption was therefore that the elimination of damaging free radicals would also reduce the inflammatory risk in subjects with existing illnesses.
It was ultimately proven that the supplementation of L-cysteine reduces inflammatory reactions in the body promoting an acceleration of healing processes without complications ort side-effects. 3.

L-cysteine combats Osteoporosis

Cysteine helps combat osteoarthritis

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A further application of this semi-essential amino acid is the therapy of osteoporosis especially in older women.  The continuous reduction of bone tissue may increasingly lead to a loss of bone density and ultimately fractures.
It was suspected in the past that low bone density is often correlated with low L-Cystine concentration in the blood plasm. A study ultimately proved this inverse correlation between increased risk of osteoporosis and L-cysteine supplementation. 4.
It was shown that the supplementation of L-cysteine was able to significantly decrease the osteoporosis. It was able to reduce the activity of the osteoclasts whilst increasing synthesis of collagen , reversing both effects that subjects with Osteoporosis suffer from.
L-cysteine may therefore be classed as an extremely important remedy of orthomolecular medicine einzustufen and is used increasingly to treat conditions such as above. Although side effects are virtually non existent, diabetics should discuss the consumption of dietary L-cysteine supplements with their doctor first, because L-cysteine can reduce the concentration of insuline in the blood requiring an adjustment in the antidiabetic medicine.
Other roles are the detoxification of the body’s excess sulphuric acid and the protection of cells of free radicals with its strong antioxidant properties. It can also contribute to building Glutathione the body’s main antioxidant when combined with Glycine and Glutamic acid.

Glutathione is instrumental for the reduction of used (oxidised) Vitamin C and E.

L-cysteine can also neutralise copper poisoning and protect cells from harmful substances, which usually result from nicotine or tobacco consumption.

Foods containing lots of L-cysteine

Healthy, balanced diet

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L-cysteine levels in the body should always be kept high by consuming supplements in addition to a healthy diet, because it helps to fulfil a multitude of functions.  Many foods rich in protein usually contain L-cysteine, although usually in small amounts.
The diet should be as varied as possible and complimented with dietary supplements in order to ensure the ingestion of sufficient L-cysteine.
Meat and Soy products are best suited to cover the minimum daily required amounts of  1.400 mg L-cysteine. Pork and Chicken are particularly high in L-cysteine with 220 bis 240 mg per 100 g. Raw salmon (approximately 219 mg per 100 g) and chicken eggs (approximately 272 mg per 100 g) are also for an appropriate supply of L-cysteine.

Vegetarians can get their supply from sunflower seeds (approximately 451 mg per 100 g) and walnuts (approximately 208 mg per 100 g). Soybeans have the highest concentration with approximately 655 mg per 100 g.


L-cysteine is today often classed as a semi-essential amino acid due to its ability to neutralise toxic heavy metals in the body.

It plays an important role in the synthesis of structural proteins and thus contributes to the stiffness and stability in the connective tissue. L-Cystein protects nerves from oxidation and is thus able to prevent illnesses such as Alzheimer or Parkinson.

Last but not least, the immune system benefits particularly from an appropriate supply of this multifunctional amino acid.

It supports the building of the crucial macrophages and in doing so protects the body from infections.

Studies about L-cysteine:

  1. “Ciftci H, et. al. (2009). Effects of N-acetylcysteine on semen parameters and oxidative/antioxidant status. Urology. Volume 74, Issue, (pp. 173-6).”
  2. ‘Safarinejad, M and Safarinejad, S. (2009). Efficacy of selenium and/or N-acetyl-cysteine for improving semen parameters in infertile men: a double-blind, placebo controlled, randomized study. The Journal of Urology. Volume 18, Issue 2, (pp. 741-51).”
  3. “ScienceDaily: Targeting oxidized cysteine through diet could reduce inflammation and lower disease risk; Mar. 31, 2009
  4. “Baines M et al.: The Association between cysteine, bone turnover, an low bone mass; Calcif Tissu Int. 2007