Creatine (Kreatin)
Creatine (kreatin in 19th-century notation) is a nitrogenous organic compound found naturally in vertebrate muscle tissue, where it participates in the phosphagen energy system. In the 1840s Liebig analysed it as one of the characteristic water-soluble constituents of fresh meat and identified it as part of the nitrogenous fraction he associated with nutritive value. Swedish chemist August Almén’s critical analysis of LEMCO established that creatine and its catabolite creatinine are the primary nitrogenous constituents of the extract. Almén characterised these compounds as metabolic waste products without nutritive value: creatinine is in fact excreted via the kidneys as a waste product of creatine metabolism, and creatine itself, while a normal and functional muscle metabolite, contributes nothing to tissue protein synthesis or caloric supply in the quantities present in the extract.
The irony documented by Almén: the very compound Liebig and LEMCO cited as evidence of nutritive potency was evidence of the extract’s failure to capture meat’s real nutritive content. Creatine is present in high concentration in fresh muscle precisely because it is water-soluble and diffuses readily into the broth on cooking; the actual proteins, fats, and myosin that constitute meat’s nutritive value are not water-soluble and remain in the depleted meat residue.