L-cysteine: benefits, dosage, contraindications

L-cysteine is a semi-essential amino acid used in protein synthesis. Although the body can produce it from the amino acid methionine, L-cysteine plays several key roles that support overall health. Its side chain contains sulfur, which is crucial for the formation of disulfide bonds that help stabilize protein structures. It is important not to confuse L-cysteine with N-acetylcysteine (NAC); although the two are related, their uses and benefits are slightly different. Beyond its contribution to protein structure, L-cysteine is involved in the synthesis of several vital compounds, including glutathione, a powerful antioxidant that protects cells from damage caused by free radicals and toxins. It also contributes to the production of taurine, sulfate, and coenzyme A, which are essential for proper metabolic function and cardiovascular health. Found naturally in certain foods such as soy, meats, or nuts, the dietary requirement for L-cysteine is usually low because it is synthesized endogenously. However, it is often used as a supplement for its antioxidant effects and to support glutathione production, particularly in situations where the body is exposed to increased oxidative stress, such as during chronic illness or recovery after intense physical exertion. Although L-cysteine is being explored for its potential therapeutic effects in various conditions such as addictions or the cosmetic appearance of hair and nails, it is important to note that scientific evidence regarding its effectiveness in these areas remains limited.