NOTE: In the US, nutraceuticals are marketed under the Dietary Supplement and Health Education Act of 1994 (DSHEA). Consequently, scientific data supporting claimed benefit(s) are not always available for nutraceuticals as they are for traditional pharmaceuticals since nutraceuticals are not regulated as drugs. Monographs on nutraceuticals are included in CP when reliable clinical data are available. The information presented below is condensed from the best clinical data we could find.
L-lysine is an essential amino acid, meaning it cannot be synthesized in the body and must be ingested daily via the diet or via supplementation. The normal US diet results in ingestion of >= 5 g of this amino acid daily. Orally and topically, L-lysine is commonly used to prevent and treat the clinical symptoms of herpes simplex labialis. In 1992, the FDA determined that no orally administered active ingredient was recognized as safe and effective for OTC use to treat or relieve the symptoms of cold sores. Thus, L-lysine products are marketed as nutritional supplements under DSHEA versus approved OTC drugs. L-lysine is also used orally as a protein-supplement by athletes for improving athletic performance; L-lysine is thought to enhance anabolic processes which promote muscle tissue accretion. Because L-lysine may be important in calcium absorption and homeostasis, some authors have suggested a potential use of this amino acid in the treatment of osteoporosis.1
Actions: L-lysine is an essential amino acid, and contributes to protein- and enzyme-synthesis. Amino acids reduce catabolism. L-lysine may be involved in the cellular absorption, regulation, and utilization of calcium.
Anti-viral activity: L-lysine has an inhibitory effect on the multiplication of herpes simplex type 1 virus in vitro. Lysine appears to be an anti-metabolite; it competes with arginine for inclusion into viral replicative processes (the herpes simplex virus is highly dependent on arginine).2
Uses/Documentation: •Herpes simplex type 1 (HSV-1): Available studies are equivocal; most are poorly designed. Oral L-lysine prophylaxis overall does not appear to affect the overall 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 subjective decreases in healing-times of active lesions in some open studies; other trials have not found a reduced time-to-healing of lesions or improved lesion appearance compared to placebo. Most experts have concluded that orally administered L-lysine does not objectively improve the healing of cold sores, but supplementation may decrease recurrences or improve symptomatic complaints in certain individuals.34
•Ergogenesis: Current data suggest that L-lysine supplementation does not enhance hGH or insulin secretion compared to results obtained with exercise alone, and reputable data suggest it is not an effective ergogenic. Consumption of normal high-protein foods should be adequate to meet increased dietary needs induced by high-intensity exercise.
Contraindications/Precautions: NOTE: Nutraceuticals should be used cautiously in young children and pregnant females. Because amino acids are broken down into nitrogenous wastes, excessive lysine supplementation should be avoided by those with kidney or hepatic disease.
Drug Interactions: Calcium salts and calcium supplements: When administered orally, L-lysine may increase dietary calcium absorption; L-lysine may also decrease urinary calcium excretion.
Adverse Reactions: Diarrhea or abdominal pain upon ingestion of >= 10 g/day. An isolated case of interstitial nephritis with eventual progression to chronic renal failure has been reported.5
- 1. Civitelli R, et al. Dietary L-lysine and calcium metabolism in humans. Nutrition 1992;8:400—5.
- 2. Flodin NW. The metabolic roles, pharmacology and toxicology of lysine. J Am Coll Nutr 1997;16:7—12.
- 3. Griffith RS, et al. Success of L-lysine therapy in frequently recurrent herpes simplex infection. Treatment and prophylaxis. Dermatologica 1987;175:183—90.
- 4. Walsh DE, et al. Subjective response to lysine in the therapy of herpes simplex. J Antimicrob Chemother 1983;12:489—96.
- 5. Lo JC, et al. Fanconi's syndrome and tubulointerstitial nephritis in association with L-lysine ingestion. Am J Kidney Dis 1996;28:614—7.