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Other name(s):

a-amino-b-thiolpropionic acid

Unsubstantiated claims

Please note that this section reports on claims that have not yet been substantiated through studies.

Cysteine may help treat arthritis (L-cysteine) and hardening of the arteries. It may also help treat certain lung diseases. These include bronchitis, emphysema, and tuberculosis. It may help protect the lungs from cigarette smoke.

Cysteine is said to help protect the liver from alcohol and prevent hangovers. It may also reduce the risk of damage to brain cells from alcohol.

Cysteine may play a role in the normal growth rate of hair. Cysteine may also help reduce the effects of aging on the skin. It may help healing after surgery or burns and protect the skin from radiation injury.

Cysteine is also claimed to help burn fat and increase muscle mass.

Recommended intake

Amino acids (AAs) are available as individual AAs or in AA combinations. They also come as part of multi-vitamins, proteins, and food supplements. The forms include tablets, fluids, and powders.

Note that by eating enough protein in your diet, you get all of the amino acids you need.

There are no conditions that increase how much cysteine you need.

Side effects, toxicity, and interactions

Using a single amino acid supplement may lead to negative nitrogen balance. This can decrease how efficient your metabolism is. It can also make your kidneys work harder. In children, taking single amino acid supplements may also cause growth problems.

You should not take high doses of individual amino acids for long periods of time.

Women who are pregnant or breastfeeding should not use cysteine supplements.

You should not use cysteine if you have diabetes or cystinuria (a rare genetic issue that causes cystine kidney stones). Cysteine may interfere with how insulin works.

Online Medical Reviewer: Brittany Poulson, RD
Online Medical Reviewer: Wilkins, Joanna, R.D., C.D.
Date Last Reviewed: 8/1/2016