an essential amino acid, vegetarian & vegan diets may provide little, pure usp grade material, the grade used for clinical nutrition, not animal feed!, vegetarian & vegan friendly tablets & a relevant dose, manufactured to gmp standardslysine is termed an essential amino acid as it is one of the eight amino acids that our bodies can not make & so we are completely reliant on our diets to provide lysine. we require 2-3 g a day of lysine & it is most abundant in animal based foodstuffs such as meat. there is very little lysine in most vegetables & even vegetable proteins are not particularly high in lysine, & so some experts believe that vegetarian & vegan diets may provide rather low levels of lysine. the body uses amino acids to build proteins that are essential for the maintenance of muscle mass & normal bones. huge quantities of lysine are used in agriculture as it is the only amino acid that is routinely added to animal feeds. however we use a grade called usp meaning its quality & purity makes it suitable for clinical nutrition products. very cheap lysine products may be based on the lower grade, less purified animal feed grade.