L-lysine is an essential amino acid; it must be ingested or injected as a supplement since it cannot be synthesized by the body. Supplementation and topical applications of L-lysine are used to prevent the treatment of herpes simplex labialis. In 1992, the FDA determined that no orally administered active ingredient or OTC treatment was recognized as a safe and effective treatment for cold sores; this means that L-lysine products are marketed as nutritional supplements under DSHEA, not approved OTC drugs. L-lysine is also used orally by athletes to improve performance, because it is believed to enhance anabolic processes which encourage the growth of muscle tissue. Because L-lysine may support calcium absorption and homeostasis, some researchers have suggested it as a treatment for osteoporosis.
L-lysine contributes to protein and enzyme synthesis. L-lysine may also be involved in the cellular absorption and regulation of calcium.
Anti-viral activity: L-lysine inhibits the multiplication of herpes simplex type 1 virus in vitro. Lysine appears to be an anti-metabolite, which means it competes with arginine for inclusion into viral replicative processes. The herpes simplex virus depends on arginine, so competition can suppress its growth.
Herpes simplex type 1 (HSV-1): Few reliable studies are available, but oral L-lysine prophylaxis does not appear to reduce the recurrence rate of HSV-1 lesions. However, some L-lysine-treated patients were recurrence-free in a few studies. L-lysine has been associated with decreases in active lesion healing-times in some open studies; other trials have not found this effect when compared to placebo. Most experts have concluded that orally administered L-lysine does not improve the healing of cold sores, but supplementation may decrease recurrences or improve symptoms in some patients.
Ergogenesis: Studies suggest that L-lysine supplementation does not enhance hGH or insulin secretion compared to exercise alone, and it does not appear to be an effective ergogenic. A diet of normal high-protein foods should meet increased the increased dietary needs induced by intense exercise.
Renal Impairment: Administration of levocarnitine to patients with end-stage renal disease (ESRD) on hemodialysis can increase plasma levocarnitine concentrations. Chronic administration of high doses of oral levocarnitine in patients with severe renal impairment or in ESRD patients on dialysis may result in accumulation of the accumulation of toxic metabolites that are normally excreted in the urine. The metabolites do not accumulate to the same extent following intravenous administration.
Nutraceuticals should be used cautiously in children and pregnant patients. L-lysine supplementation should be avoided by those with kidney or hepatic disease.
Calcium salts and calcium supplements: Orally administered L-lysine may increase dietary calcium absorption and may decrease urinary calcium excretion.