Lysine is an essential amino acid. This means that it must
be obtained through the diet in adequate quantities to meet the body's needs.
Lysine is required in the body for the manufacture of
carnitine, which is an amino acid used for the proper metabolism of fats.
Lysine incorporated into proteins if often cross-linked, such as in the body
proteins collagen and elastin (the major proteins of the body). Cross-linking
of lysine to make proper collagen and elastin is dependent upon the enzyme
lysloxidase, which requires copper. Copper deficiency, therefore, can result in
imperfections in collagen or elastin. Lysine has also been found to stimulate
the synthesis of cholesterol in the liver. High lysine to arginine ratio diets,
as found in animal protein, stimulate cholesterol synthesis, whereas lower
lysine to arginine ratio diets do not stimulate as much cholesterol synthesis.
Lysine deficiency can interfere with carnitine synthesis
and have adverse impact upon fat metabolism to energy.
Lysine supplementation is helpful in the management of
herpes infections. The mechanism of the action of lysine in the treatment of
herpes infections is not yet known, but appears to have some effect upon the
replication of the herpes virus in infected cells. Doses range between 400 and
It is commonly a limiting amino acid in strict vegetarian
diets in that it is in short supply in many vegetable grains. "Limiting amino
acid" means that its shortage in the diet may limit the synthesis of body
protein and enzymes.
An unusual feature of lysine metabolism is that the
alpha-amino group does not equilibrate with the nitrogen pool, as it does with
most amino acids. Lysine can actually be broken down by four different pathways
and is one of the more closely regulated essential amino acids in intermediary
metabolism. Lysine is used along with methionine in the manufacture of
carnitine, which is important for fatty acid metabolism. Lysine is also very
important for the synthesis of ribosomal proteins and its insufficiency in the
diet can result in poor protein biosynthesis. By degradation of lysine to
gamma-butyro betaine, it can then be converted on to carnitine. These steps
require ascorbic acid (vitamin C) for their reactivity.
Cottage cheese (dry) 3,500 mg/cup
Cottage cheese (crmd) 2,562 mg/cup
Fish & other seafoods 1,500-11,800 mg/lb
Meats 2,000-8,500 mg/lb
Poultry 4,500-6,500 mg/lb
Sesame seeds 1,200 mg/cup
Dry, whole lentils 3,000 mg/cup
Excessive intake of lysine can result in increased urinary
spill of lysine and kidney problems; therefore, doses above 1,500 mg per day
should not be used. Because lysine has an effect on cholesterol synthesis in
the liver, its use may slightly elevated LDL cholesterol.