What is Lysine?
L-lysine, commonly known as lysine, is one of the indispensable, essential, amino acids for humans. Lysine is not produced in the body and thus it needs to be obtained from dietary sources or as a supplement. Lysine is one of the amino acids that constitute proteins.
Health Benefits of Lysine
A well-known benefit of lysine is for the prevention and treatment of herpes: cold sores, (caused by herpes simplex virus-1) and genital herpes (caused by herpes simplex virus-2). Lysine may also increase absorption of calcium and reduce excretion of calcium and thus lower the severity of osteoporosis. Lysine is also the substrate for the synthesis of amino acid carnitine, which in turn is an important substrate in the process of energy generation. Other lysine benefits include improving the immune system and promotion of overall well-being.
There is also a hypothesis that suggests an association between consumption of foods high in lysine and low in arginine and lower risks of incidence of Alzheimer’s disease.
Lysine, Arginine and Herpes
L-arginine is an amino acid required by the herpes virus for its reproduction. And the mechanism by which lysine helps in the treatment of cold sores and genital herpes is by reducing the availability of arginine for the herpes virus. Both lysine and arginine compete for absorption in the intestine, re-absorption in the kidney and transport vehicles to the cell. Thus, a high lysine to arginine ratio allows lysine to outcompete arginine and starve the herpes virus the amino acid required for its replication. Besides, lysine increases the breakdown of arginine by stimulating the enzyme arginase.
Lysine Daily Requirement
The daily lysine requirement is higher for infants than adults. However, the amount of the estimated daily requirement for lysine varies from study to study. Tables 1a and 1b show different estimates of the lysine requirement.
Table 1a: Daily lysine requirements of infants, children, adolescents and adults (Source: Tome and Bos, 2007)
|Age ( in years)||Lysine requirement (mg/kg body/day)|
|4 - 10||45|
|10 - 18||34 - 36|
Table 1b: Lysine daily requirements for infants, childeren, adolescents and adults (Source: FAO).
|Age||Lysine requirement (mg/kg body/day)|
|3 - 4 months||103|
|10-12 yrs||44 - 60|
Food Sources High in Lysine Content
Lysine is found in high amounts in high protein foods. Lysine is generally low in cereal foods, except in wheat germ. Based on the USDA Nutrition Laboratory analysis of common foods in the US, high lysine foods include seal and whale meat, soy protein isolate, egg (the white part), cod, and parmesan cheese. A Western diet, for adults, provides on average 6 – 10 grams per day.
The tables below show the top highest lysine foods (Table 2) of all food categories and also top highest lysine food sources in each food category (Tables 3 - 6).
Table 2: Top 14 foods high in Lysine content.
|Rank||Lysine food source||Lysine content (g/g of edible food portion)|
|1||Seal, bearded (Oogruk), meat, dried (Alaska Native)||6.69|
|2||Whale, beluga, meat, dried (Alaska Native)||6.31|
|3||Fish, cod, Atlantic, dried and salted||5.77|
|4||Egg, white, dried||5.52|
|5||Soy protein isolate, PROTEIN TECHNOLOGIES INTERNATIONAL, SUPRO||5.50|
|6||Soy protein isolate||5.33|
|7||Egg, white, dried, powder, glucose reduced||5.08|
|8||Seal, bearded (Oogruk), meat, partially dried (Alaska Native)||5.05|
|9||Fish, whitefish, dried (Alaska Native)||4.77|
|10||Egg, white, dried, flakes, glucose reduced||4.74|
|11||Soy protein concentrate, produced by acid wash||3.93|
|12||Cheese, parmesan, dry grated, reduced fat||3.84|
|13||Smelt, dried (Alaska Native)||3.69|
|14||Gelatins, dry powder, unsweetened||3.46|