an essential amino acid,vegetarian and vegan diets may provide little,pure usp grade material,the grade used for clinical nutrition, not animal feed!, vegetarian and vegan friendly tablets and 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 and so we are completely reliant on our diets to provide lysine. we require 2-3 g a day of lysine and it is most abundant in animal based foodstuffs such as meat. there is very little lysine in most vegetables and even vegetable proteins are not particularly high in lysine, and so some experts believe that vegetarian and 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 and 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 and purity makes it suitable for clinical nutrition products. very cheap lysine products may be based on the lower grade, less purified animal feed grade.