This knowledge aids in understanding how drugs, prescription and non-prescription, have to be used, if at all. How the mere act of smoking tobacco results in carbon exhaled, for example. This can lead to a study of pharmacology and how the knowledge affects the individual. The effect of marijuana, cocaine, L.S.D. and others on thought processes can be stated as action and reaction data. Even the effect of psychopharmacologists, and neuropharmacologists working on experimental drugs to boost mental sharpness, can be better understood when one learns more of chemical brain carriers.
Urine testing is also a good way to determine the results of body metabolism.