Lactic acid is an organic acid typically derived from sugar through a process known asfermentation. This is a process in which microorganisms convert carbohydrates, like sugar, into alcohol and then an acid. Lactic acid is commonly found in foods that have fermented.

The compound was first identified by an eighteenth century Swedish chemist named Carl Wilhelm Scheele. In the following century, French chemist and microbiologist Louis Pasteur discovered that lactic acid was turning the vintage burgundy wine of France sour. During the process of making wine using yeast to ferment grape sugar into alcohol, bacteria had contaminated the mixture and through fermentation converted the sugar to lactic acid rather than alcohol

Since 1850, with the work of French physiologist Claude Bernard, it was known that the human liver stored a sugar called glycogen, and that this sugar was present in human muscle tissue ready to be converted...