Lysine is an essential amino acid that is not synthesized in adequate amounts by the body, so it must be obtained from dietary sources. Lysine furnishes the structural components for the synthesis of carnitine, which promotes fatty acid synthesis within the cell. It is particularly important for proper growth. Lysine also regulates calcium absorption and plays an important role in the formation of collagen.

A vegetarian diet may not provide sufficient lysine. Among protein sources, plants often contain insufficient sources of lysine. Lysine is the limiting amino acid of many cereals. In many areas of the world where diets are grain-based, this becomes important as a lysine deficiency can create a negative nitrogen balance and lead to kidney stones. Lysine deficiency may be characterized by fatigue, nausea, dizziness, appetite loss, emotional agitation, decreased antibody formation, decreased immunity, slow growth, anemia, reproductive disorders, pneumonia, acidosis, and bloodshot eyes.

Lysine has been used to treat herpes infections caused by both herpes simplex viruses and herpes zoster. Supplementation can improve recovery speed and suppress recurrences of infections. Some studies have found lysine of potential benefit in treating cardiovascular disease, osteoporosis, asthma, migraines, nasal polyps, and postepisiotomy pain.

Generally, lysine is found in the following foods:

• Meat, particularly red meats
• Cheeses
• Poultry
• Sardines
• Nuts
• Eggs
• Soybeans

The most concentrated sources are torula yeast, dried and salted cod, soybean protein isolate, soybean protein concentrate, Parmesan cheese, pork loin (excluding fat), dried and frozen tofu, freeze-dried parsley, defatted and low-fat soybean flour, fenugreek seed, and dried spirulina seaweed.

Lysine is an essential amino acid. Chemically, lysine is unique among the amino acids in that it possesses two amino (NH2) groups. The extra amino group can react with other substances, such as glucose or lactose, creating an amino–sugar complex that cannot be split by digestive enzymes, thus reducing the availability of lysine.

Lysine is also known as LYS, amino acid K, and 2-diamino-hexaenoic acid. Its chemical composition is C6H13NO2.

• L-lysine acetylsalicylate (LAS)
• Lysine clonixinate (LC)
• L-lysine monohydrochlorine (LMH)

• Asthma: LAS, when administered by inhalation, has been shown to protect against histamine-induced bronchoconstriction.
• Herpes: Supplementation may improve recovery speed and suppress recurrences of infections.
• Migraine: Treatment with a combination of LAS and metoclopramide may be effective.
• Nasal polyps: Recent research suggests that LAS may prevent relapses of nasal polyps.
• Postepisiotomy pain: 125 mg/day of LC was found to reduce postepisiotomy pain in primiparous patients with moderate to severe postepisiotomy pain.

The following are the recommended dietary allowances, according to the National Research Council.

• Birth to 4 months: 103 mg/kg/day
• 5 months to 2 years: 69 mg/kg/day
• 3 to 12 years: 44 mg/kg/day
• Adults and teenagers: 12 mg/kg/day

Based on obligatory amino acid losses (including data from amino acid tracer studies), it has been suggested that adults need 30 mg/kg/day.

Nutritional doses are 1 to 3 g per day.

Lysine appears to be nontoxic.

L-lysine may increase cholesterol and triglyceride levels.

No clinically significant interactions between lysine and conventional medications are known to have been reported in the literature to date.

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