Lactates

Lactates are the salts and esters of lactic acid, the simplest hydroxycarboxylic acid. In aqueous solution, lactic acid dissociates to lactate (the conjugate base) and a proton; at physiological pH, lactate is the dominant species. Common lactates include sodium lactate, potassium lactate, and calcium lactate.

Biologically, lactate is produced from pyruvate by lactate dehydrogenase during anaerobic glycolysis, allowing glycolysis to continue by regenerating NAD+. Lactate is released into the bloodstream and transported to the liver, where it can be reoxidized to pyruvate and used for gluconeogenesis (the Cori cycle). It can also serve as an energy source for the heart and skeletal muscles and may function as a signaling molecule in some tissues. Enantiomers exist; L-lactate is predominant in human metabolism, while D-lactate is produced by some bacteria and, in excess, can contribute to metabolic acidosis in certain conditions.

Clinically, blood lactate is measured as a marker of tissue perfusion and metabolic status. Hyperlactatemia can indicate hypoxia, sepsis, shock, or strenuous exercise. Persistent elevation or inability to clear lactate after treatment correlates with worse outcomes. Lactic acidosis is a category of metabolic acidosis caused by excess lactate, though lactate is rarely the sole contributor.

Industrial and food uses include sodium lactate and potassium lactate as humectants, buffering agents, and acidity regulators, and calcium lactate as a calcium supplement. Lactate salts are also produced by fermentation with lactic acid bacteria and are used in fermented foods such as yogurt, sauerkraut, and pickles.