Lysine, or L-lysine, is an essential amino acid, meaning it is necessary for human health, but the body cannot make it. You have to get lysine from food or supplements. 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 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, tendons, and cartilage.

Most people get enough lysine in their diet. Although athletes, burn patients, and vegans who do not eat beans may need more. If you do not have enough lysine, you may experience:

• Fatigue
• Nausea
• Dizziness
• Loss of appetite
• Agitation
• Bloodshot eyes
• Slow growth
• Anemia
• Reproductive disorders

For vegans, legumes (beans, peas, and lentils) are the best sources of lysine.

Herpes simplex virus (HSV)

Some studies suggest that taking lysine on a regular basis may help prevent outbreaks of cold sores and genital herpes. Others show no improvement. Lysine has antiviral effects by blocking the activity of arginine, which promotes HSV replication. One review found that oral lysine is more effective atpreventing an HSV outbreak than it is at reducing the severity and duration of an outbreak. One study found that taking lysine at the beginning of a herpes outbreak did not reduce symptoms. Most experts believe that lysine does not improve the healing of cold sores. But supplementation may reduce recurrences or improve symptoms.

Osteoporosis

Lysine helps the body absorb calcium and reduces the amount of calcium that is lost in urine. Since 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.

Athletic performance

Athletes sometimes use lysine as a protein supplement. Some studies suggest lysine helps muscle tissue recover after stress.

Good sources of lysine include foods that are rich in protein, such as:

• Meat, specifically red meat, pork, and poultry
• Cheese, particularly parmesan
• Certain fish, such as cod and sardines
• Eggs
• Soybeans, particularly tofu, isolated soy protein, and defatted soybean flour
• Spirulina
• 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

Speak with your pediatrician regarding appropriate dosages. Dosage is usually adjusted based on body weight.

Adult

Dosing depends on different factors. Talk to your doctor to determine the right dose for you.

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

Lysine can increase the absorption of calcium. Use caution when taking large amounts of calcium while supplementing with lysine.

While lysine in the diet is considered safe, excessive doses may cause gallstones. There have also been reports of renal dysfunction, including Fanconi syndrome and renal failure.

Talk to your doctor before taking supplemental lysine if you have kidney disease, liver disease, or if you are pregnant or breastfeeding.

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 doctor.

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

Aminoglycoside antibiotics (gentamicin, neomycin, streptomycin, etc.): Use with lysine may increase the risk of nephrotoxicity.

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

Breau RH, Kokolo MB, Punjani N, et al. The effects of lysine anaolgs during pelvic surgery: a systematic review and meta-analysis. Transfus Med Rev. 2014;28(3):145-55.

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.

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

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.

Rakel D. Integrative Medicine. 3rd ed. Philadelphia, PA: Elsevier Saunders; 2012.

Rao M, Chinnasamy N, Hong JA, et al. Inhibition of histone lysine methylation enhances cancer-testis antigen expression in lung cancer cells: implications for adoptive immunotherapy of cancer. Cancer Res. 2011;71(12):4129204.

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.