Cysteine quick review

• Description: a nonessential amino acid, a naturally occurring hydrophobic amino acid which has a sulfhydryl group and is found in most proteins.

• Health benefits: strengthens the protective lining of the stomach and intestines, increases levels of the antioxidant glutathione.

• Sources & dosage: ricotta, cottage cheese, yogurt, pork, sausage meat, chicken, turkey, duck, luncheon meat, wheat germ, granola, and oat flakes.

• Deficiency symptoms: slowed growth in children, decreased levels of serum essential proteins, apathy, loss of pigmentation in hair, edema, lethargy.

• Side effects: nausea, vomiting and other gastrointestinal disturbances. D-cysteine, D-cystine, and 5-methyl cysteine are toxic and should be avoided.

N-A-C by Jarrow Formulas

N-Acetyl-L-Cysteine (NAC) is an amino acid and antioxidant. It is a precursor in the body to the critical antioxidant glutathione, which is produced intracellularly, primarily by the liver. Glutathione exerts a variety of protective effects, including detoxification and intracellular defense against oxidative stress. Substances known to reduce glutathione status are acetaminophen and alcohol. N-A-C by Jarrow Formulas is manuafactured according to the highest pharmaceutical standards and uses only the best quality raw ingredients. Click here for more information.

Cysteine

Cysteine, a nonessential amino acid, is one of the 20 building blocks of protein. Cysteine is a part of organic molecules containing an amino group, which can combine in linear arrays to form proteins in living organisms. Cysteine can be synthesized by the body and is not essential to the diet. Its key chemical feature is a thiol group that contains sulfur. Cysteine is a naturally occurring hydrophobic amino acid which has a sulfhydryl group and is found in most proteins, however only in small quantities. When it is exposed to air it oxidizes to form cystine, which is two cysteine molecules joined by a disulfide bond. One molecule of water (H2O) is the byproduct from the creation of each molecule of cystine. It can be taken as a supplement in the form of N-acetylcysteine (NAC). N-acetyl-L-cysteine (NAC) helps break down mucus and detoxify harmful substances in the body. Both cysteine and NAC have been shown to increase levels of the antioxidant glutathione. This thiol group can combine with the thiol group of another cysteine to form a disulfide bridge, which helps structural proteins and enzymes maintain their configuration. Two cysteine molecules linked by a disulfide bridge make up the amino acid cystine.

Cysteine functions, uses, and health benefits

Cysteine is one of the key components in all living things. Proteins are synthesized by formation of peptide bonds during ribosomal translation of messenger RNA. Cysteine plays a key role in stabilizing extracellular proteins. Cysteine strengthens the protective lining of the stomach and intestines, which may help prevent damage caused by aspirin and similar drugs. In addition, cysteine may

play an important role in the communication between immune system cells. Cysteine can react with itself to form an oxidized dimer by formation of a disulfide bond. The environment within a cell is too strongly reducing for disulfides to form, but in the extracellular environment, disulfides can form and play a key role in stabilizing many such proteins, such as the digestive enzymes of the small intestine. Cysteine is occasionally converted into glucose and used as a source of energy. Cysteine is one of the few amino acids that contains sulfur. This allows cysteine to bond in a special way and maintain the structure of proteins in the body. Cysteine is a component of the antioxidant glutathione. The body also uses cysteine to produce taurine, another amino acid. Cysteine is believed to play a role in the normal growth rate of hair. Cysteine may possibly help reduce the effects of aging on the skin, assist in healing after surgery or burns, and help protect the skin from radiation injury.

N-acetyl cysteine (which contains cysteine) is the most frequently used form of cysteine. N-acetyl-L-cysteine (NAC) helps break down mucus and detoxify harmful substances in the body. Both cysteine and NAC have been shown to increase levels of the antioxidant glutathione. Antioxidants are substances that scavenge free radicals, damaging compounds in the body that alter cell membranes, tamper with DNA, and even cause cell death. Oral or intravenous NAC is commonly used to prevent or reduce liver and kidney damage associated with overdoses of acetaminophen, an over the counter medication commonly used for pain or headache. NAC may help dissolve mucus and improve symptoms associated with chronic bronchitis, asthma, cystic fibrosis and emphysema. Chronic smokers also may benefit from NAC supplementation. NAC may help prevent changes caused by smoking in cells lining the respiratory passage. Supplementation with cysteine may help strengthen the immune system in those with HIV and diminish the bodily damage associated with this infection. N-acetyl-L-cysteine (NAC) may improve symptoms associated with Sjogren's syndrome, enhance cognitive functioning in some individuals with Alzheimer's disease, prevent development of cataracts and macular degneration, and slow down motor impairment in amyotrophic lateral sclerosis.

Dietary sources of cysteine

The body can synthesize cysteine from methionine and other building blocks. Cysteine, the amino acid from which NAC is derived, is found in most high-protein foods including ricotta, cottage cheese, yogurt, pork, sausage meat, chicken, turkey, duck, luncheon meat, wheat germ, granola, and oat flakes.

Cysteine dosage, intake

Most people do not need to supplement cysteine. There is no specific pediatric recommendation for cysteine. Recommended adult doses of NAC vary depending on the health condition being treated. NAC is administered either intravenously or orally in the hospital to treat acetaminophen (paracetamol) poisoning in both children and adults. Typical dosage recommendations are in the range of 250-1500mg of NAC daily for the majority of therapeutic benefits. Those who supplement with l-cysteine should drink at least six to eight glasses of water daily in order to prevent cystine renal stones.

Cysteine deficiency

Cysteine deficiency is rare, but may be seen in vegetarians with low intake of the plant foods containing methionine and cysteine. Cysteine deficiency can lead to reduced production of the essential peptide glutathione. Glutathione acts as an intracellular detoxifying agent and is important in maintaining hepatic function. Glutathione protects the liver by neutralizing free radicals, which have a deleterious effect on all tissues in the body. A deficiency of this amino acid may either contribute to, or result from, immune suppression associated with HIV. Symptoms of cysteine deficiency include slowed growth in children, decreased levels of serum essential proteins, apathy, loss of pigmentation in hair, edema, lethargy, liver damage, muscle loss, skin lesions, weakness, fat loss. Adequate amounts of methionine are needed in the diet, as the precursor to cysteine, to prevent cysteine deficiency.

Toxicity, side effects, interactions, and contraindications

Cysteine is considered to be of low toxicity, even in high doses. High oral doses of N-Acetyl cysteine have been associated with nausea, vomiting and other gastrointestinal disturbances. NAC may enhance the blood pressure-lowering effects of ACE inhibitors, medications commonly used to treat high blood pressure. Treatment with NAC may enhance the effectiveness of immunosuppressive medications such as azathioprine, cyclophosphamide, prednisolone, or prednisone. N-acetyl cysteine may increase the effectiveness of corticosteroids, a class of drugs with anti-inflammatory activity. Topical applications of NAC may increase the effectiveness of oxiconazole, an antifungal medication used for athlete's foot. Some forms of cysteine are toxic and should be avoided. These include D-cysteine, D-cystine, and 5-methyl cysteine.