Lysine is an essential amino acid necessary for growth and to help maintain nitrogen balance in the body. It may help promote proper nitrogen balance in the body and inhibit glycation, the bonding of a sugar and protein or lipid molecule accelerated by elevated levels of sugar in the blood.

Lysine has many functions in the body because it is incorporated into many proteins, which are used for a variety of purposes.

Most people consume adequate amounts of lysine. However, vegans whose diets contain large amounts of grains and only minimal amounts of beans could become lysine deficient. Athletes involved in frequent vigorous exercise have an increased need for essential amino acids, although most diets meet these increased needs. Lysine supplementation has been shown to increase the absorption and retention of calcium.

Lysine works with other essential amino acids to maintain growth, lean body mass and the body's store of nitrogen. In addition, dietary supplementation with the essential amino acid L-lysine has been shown to promote relaxation in humans with low dietary intake of L-lysine. L-lysine, together with arginine, has been documented to promote healthy hormonal stress responses in humans.