Cysteine is a sulfur-containing amino acid that plays an important role in metabolism and antioxidant protection. It serves as a precursor to glutathione, one of the main intracellular antioxidants, and also participates in protein synthesis, strengthening the immune system, and maintaining the health of skin, hair, and connective tissue.
Beneficial Properties
Cysteine performs several vital functions in the body:
- involved in the synthesis of glutathione, the primary detoxifier and antioxidant of cells;
- supports the health of skin, nails, and hair due to its sulfur content;
- stimulates the immune response and accelerates tissue recovery;
- participates in the metabolism of vitamins B6 and B12, as well as iron and zinc.
With adequate consumption, cysteine helps protect the body from oxidative stress and inflammation, as well as supports overall well-being.
Daily Requirement and Sources
The recommended daily requirement for cysteine averages from 500 to 1800 mg depending on age, health status, and physical activity. In athletes, elderly individuals, and under stress conditions, the requirement may be higher.
Cysteine is classified as a conditionally essential amino acid: the body can synthesize it from methionine, but during methionine deficiency or periods of increased demand, external consumption becomes necessary.
Main dietary sources include:
- meat and offal (liver, heart);
- fish and seafood;
- eggs;
- dairy products;
- legumes and whole grain products (to a lesser extent).
Symptoms and Consequences of Deficiency
A deficiency of cysteine can lead to a decrease in glutathione levels and a deterioration of the body’s antioxidant protection.
Possible symptoms include:
- fatigue and weakness;
- frequent infections due to weakened immunity;
- skin and hair problems (brittleness, hair loss);
- slowed tissue recovery;
- increased risk of inflammation and oxidative stress.
Individuals with liver, intestinal diseases, or protein metabolism disorders are especially sensitive to cysteine deficiency.
Possible Risks of Excess and Their Manifestations
Taking high doses of cysteine, especially in supplement form, can lead to side effects.
Main manifestations of excess:
- headaches;
- digestive disorders (nausea, discomfort, diarrhea);
- unpleasant body odor and bad breath;
- increased anxiety and irritability;
- disruption of the absorption of other amino acids, especially methionine.
Long-term consumption of more than 2000 mg per day may increase the level of homocysteine – a marker of cardiovascular risks. Therefore, exceeding safe dosages without medical supervision is not recommended.
How to Maintain Optimal Levels
To maintain normal levels of cysteine:
- consume protein-rich animal products;
- if on a restricted diet, consider supplements (such as N-acetylcysteine), but only after consulting a specialist;
- ensure the intake of vitamins B6, B12, and folates that support amino acid metabolism;
- include moderate physical activities and monitor the health of your liver and kidneys.