Cysteine and Cystine

Cysteine and Cystine are sulfur-containing amino acids that are synthesized in the liver and are involved in multiple metabolic pathways. Cysteine is formed from homocysteine, which comes from the essential amino acid methionine. Cysteine can be converted to cystine and taurine. Cystine itself is a disulfide, containing two cysteine molecules. Cysteine is contained in a variety of foods and is found mainly as cystine in poultry, yogurt, oats, and wheat germ, or in the sulfur foods that contain methionine and cysteine, such as egg yolks, red peppers, garlic, onions, broccoli, and brussels sprouts.

In recent years, findings about cysteine and its many functions in the body have been exciting. It can be used to help treat a variety of problems. Cysteine can form glutathione (along with glutamic acid and glycine), a powerful antioxidant and detoxifier that functions in many enzyme systems. Glutathione is a cofactor in many important enzymes that help protect us from the harm of heavy metals, chemicals, and smoke. Cysteine is becoming even more important as a useful antioxidant-detoxifier-protector with the increasing pollution and toxicity of this industrial age. A cell membrane stabilizer, it may reduce thehazards of smoking and alcohol consumption. It specifically helps neutralize the aldehydes produced by the liver as a by-product of the metabolism of alcohol, fats, air pollutants, and some drugs. It may also be helpful in this regard by minimizing free-radical effects, which also contribute to a variety of degenerative processes. Cysteine in sufficient levels will bind with metals—preferentially, the heavy metals lead, mercury, and cadmium bond most strongly—thus, cysteine aids the body’s elimination of them. It helps promote tissue healing after surgery or burns, and it also may stimulate white blood cell activity to help in disease resistance and provide protection from mutagenesis of cells and the carcinogenic process, though further research is needed in these areas.



Smoker’s cough/bronchitis

Air pollution

Exposure to chemicals

Psoriasis (aids skin healing)

Surgery or injury (aids wound healing)

Hair loss

Infection (immune support, detoxifier)

Rheumatoid arthritis

Cataract (best in prevention)

Cancer prevention and treatment

(decreases toxicity of offending agents)

Mental illness


Metal toxicity or exposure (lead,

mercury, cadmium)


* Protects alveoli from smoke damage, along with beta carotene, zinc, and selenium.

The overall idea, then, is that L-cysteine is one of the antiaging nutrients, as aging is thought to be due mainly to oxidation and free-radical damage. It may be helpful in actually increasing our life span and can be beneficial in those inflammatory problems caused by free radicals, such as arthritis and vascular irritation. L-cysteine also forms another amino acid, L-cystine, which is important in hair and nail tissues.

L-cysteine supplementation will be discussed in the specific programs in Part Four of this book. Basically it is used in amounts commonly ranging from 250–750 mg. daily, often taken in several portions throughout the day along with three times the vitamin C to prevent crystallization of excess cystine.

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Written by Elson M. Haas MD

Explore Wellness in 2021