Lysine is an essential amino acid, which means that it is essential to human health but cannot be manufactured by the body. For this reason, lysine must be obtained from food. Amino acids 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 to lower cholesterol. Lysine appears to help the body absorb and conserve calcium and it plays an important role in the formation of collagen, a substance important for bones and connective tissues including skin, tendon, and cartilage.

If there is too little lysine in the diet, kidney stones and other health related problems may develop including fatigue, nausea, dizziness, loss of appetite, agitation, bloodshot eyes, slow growth, anemia, and reproductive disorders. It is extremely rare, however, to obtain insufficient amounts of lysine through the diet. Generally, only vegetarians who follow a macrobiotic diet and certain athletes involved in frequent vigorous exercise are at risk for lysine deficiency. For vegetarians, legumes (beans, peas and lentils) are the best sources of lysine.