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L-cysteine is found in most protein based foods, but it can also be taken in a natural or synthetic supplement form. This important amino acid has many health benefits, not least of which is its anti-aging properties.

Why You Need L-Cysteine

L-cysteine, often referred to as “cysteine”, is a non-essential and sulphur containing amino acid (building block of protein) found in the human body. It is found in beta-keratin, which is the main protein in our nails, hair and skin. L-cysteine has anti-aging properties due to its role in the process of detoxification and the synthesis of glutathione in the body, both of which result in the protection of several tissues and organs. According to recent research studies, listed on, it not only slows down the natural process of aging, but also helps in preventing dementia and multiple sclerosis, because both conditions are associated with an accumulation of toxins.  L-cysteine supports the synthesis of the highly anti-oxidative glutathione and can also be stored in this chemical form. It plays an important part in detoxification and the resulting protection of several tissues and organs. Glutathione also inhibits inflammation and leads to an overall strengthening of the immune system.

According to the National Centre for Biotechnology Information in the USA, cysteine is a crucial part of the body’s process of protein synthesis and collagen production, as well as supporting detoxification, maintenance of skin elasticity and texture, and the possibility of diverse metabolic functions. Due to the roles it plays in body function, cysteine is sometimes taken as a supplement.

The supplement comes in the form of N-acetyl-L-cysteine (NAC), which the body turns into cysteine and then into the powerful antioxidant glutathione. This assists in fighting off free radicals that have been implicated in aging, and the development of health problems such as heart disease and cancer. Although cysteine is classified as a non-essential amino acid, in rare cases it may be essential for infants, the elderly, and individuals with certain metabolic disease or who suffer from malabsorption syndromes.

This Amino Acid Will Support Healthy Body Functions

The European Food Safety Authority reports, “The amino acid L-cysteine is safe for all animal species if the requirements for sulphur amino acids are respected. The maximum amount of L-cysteine that can be safely added to the diet will depend on the levels of other sulphur-containing amino acids. “Supplemental L-cysteine will not be deposited in animal tissues as such; it will be incorporated in body proteins without causing any change in their natural composition, or it will be metabolised and excreted. The product under application does not contain substances of toxicological concern. Thus, the use of L-cysteine in animal nutrition does not raise any concerns for consumer safety.” According to South Africa’s Department of National Health and Population Development’s regulations governing the use of certain food additives in certain wheaten and rye products, South African food manufacturing companies are allowed to produce wheat meal with 30mg/kg of L-cysteine and bread products with 45mg/ kg of L-cysteine, in order to facilitate correct levels of sulphur-containing amino-acid consumption.

The only challenge you may have with the concept of added L-cysteine to your food or in supplement form, is knowing where it comes from in terms of the process of food manufacture. According to the University of Maryland Medical Centre in the USA, the majority of L-cysteine used in foods is obtained industrially by hydrolysis of human hair, poultry feathers or hog hair – with human hair being the preferred source, due to its efficiency in producing large quantities of L-cysteine.


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Synthetically produced L-cysteine, compliant with Jewish kosher and Muslim halal laws, is also available, albeit at a higher price.

Foods Containing L-Cysteine

Meat and soy products are best suited to cover the minimum daily required amounts of  1.400 mg L-cysteine. Pork, eggs, raw salmon and chicken are high in L-cysteine. If you are vegetarian you can get your L-cysteine from sunflower seeds and walnuts although soybeans have the highest concentration.


Whole Grain Smoked Salmon



Guest Writer

This post has been curated by a Longevity Live editor for the website.

The content in this editorial is for general information only and is not intended to provide medical or other professional advice. For more information on your medical condition and treatment options, speak to your healthcare professional.

One Comment

  • Lois Carol WESSELS says:

    Very interesting – pleased that there is alternate means for vegetarians to obtain L-Cysteine – thank you for the info