Besides a sufficiency of the familiar organic nutrients, any diet that is destined to maintain health for a considerable time must include certain indispensable inorganic elements, among which calcium and phosphorus are foremost. For a long time there was some debate among students of nutrition as to whether organic compounds of these elements do not have superior virtues from the standpoint of their dietary values. The same problem was discussed somewhat earlier in relation to iron. For many years the alleged advantages of preparations of "organic iron" in therapy were given prominence, particularly in pharmaceutic advertisements. Research has made it clear, however, both that so-called inorganic iron can be absorbed and that it can actually be utilized in those synthetic functions, such as blood pigment formation, for which the element is a requisite. Indeed, there is evidence further leading to the belief that the digestive processes serve to "set free"
ALIMENTARY FACTORS INFLUENCING ABSORPTION OF CALCIUM AND PHOSPHORUS. JAMA. 1924;83(23):1850. doi:10.1001/jama.1924.02660230044013