Minerals are found in every cell, tissue, and organ. They are important constituents of essential molecules such as thyroxine, hemoglobin, and vitamin B12. They serve as critical cofactors in numerous enzymatic reactions, and form the hard mineral complexes that comprise bone. Minerals serve in the maintenance of pH, osmotic pressure, nerve conductance, muscle contraction, energy production, and in almost every aspect of life. One concept that nutritionists have developed relates not only to absorption efficiency but also to mineral interactions at the site for absorption and the site of use. This concept is that of bioavailability. Bioavailability is defined as the percent of the consumed mineral that enters via the intestinal absorptive cell, the enterocyte, and is used for its intended purpose. There is another term referring to absorption that is frequently used. That is the term “apparent absorption”. This term refers to the difference between the amount of mineral consumed and that which appears in the feces.