Is Lactic Acid a Primary Chemosignal Molecule for Pair Bonding in Humans?

Objective: We propose a hypothesis that lactic acid may be a primary chemosignal molecule for pair bonding (both, mother-baby and romantic pair) in humans. Method: Published studies in humans which provided quantitation of lactic acid (or lactate) in seven body fluids, reviews on lactic acid metabolism and relevant publications which promoted the concept of putative pheromones were analyzed. Results: A total of 22 studies in humans which had quantitated lactic acid (or lactate) values in seven body fluids (breast milk, lacrimal tear, saliva, semen, sweat, urine and vaginal fluid) were analyzed. The determination method had varied among these 22 studies. Colorimetry, enzymatic, oxidation and titration, capillary electrophoresis with amperometric detection, gas chromatography and HPLC were the mainly used methods for lactic acid determination. A definite pattern of the presence of lactic acid in all the body fluids receives recognition. Six reasons for why lactic acid is a primary chemosignal for humans in mother-baby bonding and romantic pair bonding are suggested. Conclusions: Our hypothesis invite further attention on the functional versatility of lactic acid in all the body fluids of humans, and its contribution to the emotional states of excitement during pair bonding. [ABSTRACT FROM AUTHOR]