The American Dental Association describes cold sores as "annoying, painful, fluid-filled blisters" caused by the herpes simplex virus. In the December 2005 issue of "Alternative Medicine Reviews," holistic medicine specialist Alan R. Gaby, M.D., explains that the laboratory tests show that the amino acid, lysine--a component of many proteins found in humans, other animals and plants---inhibits the replication of the herpes simplex virus. In humans, Gaby says, lysine may decrease the number and severity of cold sore outbreaks.
Function
According to Gaby, lysine may fight cold sores by competing with another amino acid, arginine, that the herpes simplex virus requires to reproduce itself. Since lysine and arginine use the same receptor molecules to gain access to the inside of cells, supplementing lysine means that less arginine reaches the inside of infected cells. In addition, Gaby notes, tests on cells grown in a laboratory suggest that lysine directly opposes growth-stimulating effects of arginine on the herpes simplex virus, although these results have not been replicated in humans.
Dose
Experts disagree on the therapeutic dose of lysine to treat and prevent cold sores. Pharmacists Charles W. Fetrow, Pharm.D., and Juan R. Avila, Pharm.D., endorse 1g to 6g per day in the 2003 edition of the "Professional's Handbook of Complementary and Alternative Medicine." Gaby says 500mg to 3g per day. The University of Maryland Medical Center says 3g per day to prevent cold sores and 3g to 9g per day to treat them. All agree that large doses should be divided and taken at least three times per day to maximize absorption from the gastrointestinal tract and maintain high levels of lysine within the bloodstream.
Sources
Consuming more lysine-rich foods represents one strategy for increasing lysine intake. Excellent food sources of lysine include red meat, pork, poultry, cheese and other dairy products, eggs, fish, legumes and whole grains. Most studies on lysine and cold sores focus on lysine supplements in the form of powders, capsules or liquids, available at many health and grocery stores.
Effectiveness
According to Gaby, clinical trials evaluating the effectiveness of lysine supplements in people with cold sores have generally shown favorable results, although they have been plagued with methodological issues. For example, one six-month trial including 114 people with cold sores or genital herpes who took 800mg of lysine or a placebo by mouth three times per day concluded that lysine was significantly more effective in reducing the frequency and severity of outbreaks and promoting healing. However, more than half the participants dropped out before the study was completed and statistical significance for the final data was not reported.
Safety
Lysine does not replace conventional medical treatment for cold sores. Gaby says the long-term safety of supplementing lysine beyond the body's nutritional requirements for therapeutic purposes, such as treating or preventing cold sores, is not known. The University of Maryland Medical Center cautions that people with liver or kidney disease and women who are pregnant or nursing should abstain from using lysine supplements, except as directed by a physician. Ideally, all patients should talk to their physicians before taking lysine or any other dietary supplement.
References
- American Dental Association: Canker Sores, Cold Sores and Common Mouth Sores
- "Alternative Medicine Reviews"; Natural Remedies for Herpes Simplex; Alan R. Gaby, M.D.; December 2005
- University of Maryland Medical Center: Lysine
- "Professional's Handbook of Complementary and Alternative Medicines, 3rd Edition"; Charles W. Fetrow, Pharm.D. and Juan R. Avila, Pharm.D.; 2003
