lysine

Lysine is an essential amino acid in humans, of the L- form that is incorporated into proteins during translation. Because the body cannot synthesize lysine, it must be obtained from dietary proteins. Adequate intake is important for growth, tissue repair, and the maintenance of nitrogen balance; severe deficiency is uncommon in developed countries but can occur with very restricted diets.

Biological roles of lysine include its participation in protein synthesis and enzyme production, as well as involvement in carnitine biosynthesis, which helps fat metabolism. Lysine residues in collagen are targets for cross-linking, contributing to the strength of connective tissues. It also supports calcium absorption and may influence immune function.

Dietary sources of lysine are rich in animal products such as meat, fish, eggs, and dairy. Plant-based sources include legumes (beans, lentils), soy products, quinoa, and certain nuts and seeds. Some cereals are relatively low in lysine, so a varied diet or combining legumes with grains can help ensure adequate intake in vegetarian and vegan diets.

Lysine is available as a dietary supplement and is marketed for cold sore prevention, among other uses. Evidence for reducing herpes simplex outbreaks is mixed and should not replace standard antiviral therapy. High-dose lysine supplements can cause abdominal discomfort and diarrhea; they may interfere with arginine and should be used with caution by people with kidney disease, during pregnancy, or while lactating. As with all supplements, medical advice is recommended for specific health conditions or medications.