Carnosin (beta-alanyl-L-histidin) er et dipeptid (=to aminosyrer) -molekyl, oppbygd av aminosyrene beta-alanin og histidin. Muskel og hjernevev er rikt på Carnosin. Sammen med Carnitin ble Carnosin først påvist av en russisk kjemiker Vladimir Gulevich. Carnosin has been proven to scavenge reactive oxygen species (ROS) as well as alpha-beta unsaturated aldehydes formed from peroxidation of cell membrane fatty acids during oxidative stress. It also buffers pH in muscle cells, and acts as a neurotransmitter in the brain. It is also a zwitterion, a neutral molecule with a positive and negative end. Like carnitine, carnosine is composed of the root word carn, meaning "flesh", alluding to its prevalence in animal protein. There are no plant-based sources of carnosine. Therefore, a vegetarian or vegan diet provides little or no carnosine in comparison to the amounts found in a diet that includes meat. Carnosine can chelate divalent metal ions. Carnosine can increase the Hayflick limit in human fibroblasts, as well as appearing to reduce the telomere shortening rate. It is also considered as a geroprotector.