Lysine, or L-lysine, is an essential amino acid. That means it is necessary for human health but the body can't manufacture it; lysine has to be gotten from food. Amino acids like lysine are the building blocks of protein. Lysine is important for proper growth, and it plays an essential role in the production of carnitine, a nutrient responsible for converting fatty acids into energy and helping to lower cholesterol. Lysine appears to help the body absorb calcium, and it plays an important role in the formation of collagen, a substance important for bones and connective tissues including skin, tendon, and cartilage.

Most people get enough lysine in their diet, although athletes, vegans who don't eat beans, and burn patients may need more. Not enough lysine can cause fatigue, nausea, dizziness, loss of appetite, agitation, bloodshot eyes, slow growth, anemia, and reproductive disorders. For vegans, legumes (beans, peas, and lentils) are the best sources of lysine.

Herpes

Some studies have found that taking lysine on a regular basis may help prevent outbreaks of cold sores and genital herpes. Not every study has shown positive results, however. One study found that taking lysine at the beginning of a herpes outbreak did not reduce symptoms.

Osteoporosis

Lysine helps the body absorb calcium and decreases the amount of calcium that is lost in urine. Because calcium is crucial for bone health, some researchers think lysine may help prevent bone loss associated with osteoporosis. Lab studies suggest that lysine in combination with L-arginine (another amino acid) makes bone-building cells more active and enhances production of collagen. But no studies have examined whether lysine helps prevent osteoporosis in humans.

Foods rich in protein are good sources of lysine. That includes meat (specifically red meat, pork, and poultry), cheese (particularly parmesan), certain fish (such as cod and sardines), nuts, eggs, soybeans (particularly tofu, isolated soy protein, and defatted soybean flour), spirulina, and fenugreek seed. Brewer's yeast, beans and other legumes, and dairy products also contain lysine.

Lysine is available in tablets, capsules, creams, and liquids, and is usually sold in the L-lysine form.

Pediatric

For children ages 2 - 12: Recommendations are 23 mg/kg/day or 10 mg per pound of body weight daily. Do not use lysine in children less than 2 years of age unless under the supervision of a health care provider.

Adult

For adults ages 13 and older: Recommendations are 12 mg/kg/day.

For adults with herpes infections: To treat symptoms, take 3,000 - 9,000 mg per day in divided doses. To prevent recurrences, take 1,000 mg 3 times per day.

Because of the potential for side effects and interactions with medications, dietary supplements should be taken only under the supervision of a knowledgeable health care provider.

Lysine in the diet is considered safe. High doses have caused gallstones and a rise in cholesterol levels in animals.

People with kidney or liver disease should ask their doctor before taking supplemental lysine.

Pregnant and breastfeeding women should not take supplemental lysine without talking to their doctor.

If you are currently being treated with any of the following medications or supplements, you should not use lysine supplements without first talking to your health care provider.

Arginine -- Arginine and lysine share common pathways in the body. High levels of arginine may lower lysine levels in the body.

Beauman JG. Genital herpes: a review. Am Fam Physician. 2005 Oct 15;72(8):1527-34. Review.

Bruzzese N, Sica G, Iacopino F, et al. Growth inhibition of fibroblasts from nasal polyps and normal skin by lysine acetylsalicylate. Allergy. 1998;53:431-434.

Civitelli R, Villareal DT, Agnusdei D, Nardi P, Avioli LV, Gennari C. Dietary L-lysine and calcium metabolism in humans. Nutrition. 1992;8(6):400-405.

De los Santos AR, Marti MI, Espinosa D, Di Girolamo G, Vinacur JC, Casadei A. Lysine clonixinate vs. paracetamol/codeine in postepisiotomy pain. Acta Physiol Pharmacol Ther Latinoam. 1998;48(1):52-58.

Di Girolamo G, Zmijanovich R, de los Santos AR, Marti ML, Terragno A. Lysine clonixinate in the treatment of primary dysmenorrhea. Acta Physiol Pharmacol Ther Latinoam. 1996;46(4):223-232.

Dietary Guidelines for Americans 2005. Rockville, MD: US Dept of Health and Human Services and US Dept of Agriculture; 2005.

Fini M, Torricelli P, Giavaresi G, Carpi A, Nicolini A, Giardino R. Effect of L-lysine and L-arginine osteoblast cultures from normal and osteopenic rats. Biomed Pharmacother. 2001;55(4):213-220.

Flodin NW. The metabolic roles, pharmacology, and toxicology of lysine. J Am Coll Nutr. 1997;16:7-21.

Furst P. Dietary L-lysine supplementation: a promising nutritional tool in the prophylaxis and treatment of osteoporosis. Nutrition. 1993;9(1):71-72.

Gaby AR. Natural remedies for Herpes simplex. Altern Med Rev. 2006 Jun;11(2):93-101. Review.

Griffith RS, Walsh DE, Myrmel KH, Thmpson RW, Behforooz A. Success of L-lysine therapy in frequently recurrent herpes simplex infection. Treatment and prophylaxis. Dermatologica. 1987;175(4):183-190.

Hugues FC, Lacoste JP, Danchot J, Joire JE. Repeated doses of combined oral lysine acetylsalicylate and metoclopramide in the acute treatment of migraine. Headache. 1997;37:452-454.

Krymchantowski AV, Barbosa JS, Cheim C, Alves LA. Oral lysine clonixinate in the acute treatment of migraine: a double-blind placebo-controlled study. Arq Neuropsiquiatr. 2001;59(1):46-49.

Singh BB, Udani J, Vinjamury SP, et al., Safety and effectiveness of an L-lysine, zinc, and herbal-based product on the treatment of facial and circumoral herpes. Altern Med Rev. 2005;10(2):123-7.

Tfelf-Hansen P. The effectiveness of combined oral lysine acetylsalicylate and metoclopramide in the treatment of migraine attacks. Comparison with placebo and oral sumatriptan. Funct Neurol. 2000;15(Suppl 3):196-201.