Unlike the name suggests, lactic acid is not derived from milk.
Lactic acid is the acid ingredient of sour dairy products, fermented
fruits and vegetables and sausages. Lactic acid has been
consumed by humans since prehistoric times.
Lactic acid as a product of nature, however, is even older. It is present in every form of organized life and was supposedly already prevalent in the first forms of primitive life that existed on earth. Many bacterial species produce lactic acid, with Lactobacillus, Bifidobacterium, Streptococcus, Pediococcus and Leuconostoc being the predominant examples.
Lactic acid found in animals and humans has many functions, the most important of which is related to the supply of energy in muscle tissue. Metabolic turnover of lactic acid in adult men has been estimated to be approximately 120 to 150 g per day.