L-Lysine is protein amino acid. It is classified as an essential amino acid for humans and therefore must be supplied in the diet. Certain proteins, such as those found in meat, poultry and milk are rich in L-Lysine.
Proteins found in grains, cereals and their products are typically low in L-Lysine. For example wheat is low in L-Lysine; wheat germ, however, is rich in L-Lysine. Small amounts of free L-lysine are found in vegetables, vegetable juices and in such fermented foods as miso and yogurt.