The body does not keep a reserve store of iron on hand as is the case with calcium and phosphorus in the bone tissues, but must depend upon the daily intake in food to supply its needs. The iron content of food materials is not large, but a careful regulation of the iron bearing foods (see Table on page [5]) will make it easy to cover the demands of the body with a material which has been found to do its work most efficiently. Medicinal iron has received much attention in the determination of the essential needs of the body. “Whether medicinal iron actually serves as material for the construction of hemoglobin is not positively known, but we have what appears to be a good evidence that food iron is assimilated and used for growth and for regeneration of the hemoglobin to much better advantage than are inorganic or synthetic forms, and that when medicinal iron increases the production of hemoglobin, its effect is more beneficial in proportion as food iron is more abundant—a strong indication that the medicinal iron acts by stimulation rather than as material for the construction of hemoglobin” (Sherman).
The newborn infant has a store of iron already on hand, derived from the mother through the placenta before birth. After the birth, and through the nursing period, the child receives a certain amount of iron from the mother’s milk. This supply is not altogether reliable, however, since any disturbance of the digestion will tend to interfere with its absorption, and consequently deprive the organism of what would otherwise be used for the building up of the blood supply. Thus it is clearly indicated that the infant’s safest source of iron is from the mother during the pre-natal period. This supply must necessarily come from her diet during this time, and is made possible by regulating day by day the iron bearing foods in her dietary. After the original store of iron is reduced to that of the adult (after the child has tripled in birth-weight, generally at 12 or 13 months), and during the remainder of the growth period, it is very necessary to regulate the iron-bearing food in the diet, in order to insure the child of an adequate amount to cover the demands made by the increasing blood supply.
VITAMINES
Up to a few years ago it was believed a complete diet should contain an adequate amount of protein of a proper type, a sufficient amount of calcium, phosphorus and iron, and enough carbohydrates and fats to furnish the body with sufficient fuel to cover its energy expenditures. This belief was proved to be incorrect a number of years ago by Dr. Hopkins of England. In making certain feeding experiments with rats, Dr. Hopkins showed that some substance or substances present in milk, other than those already mentioned, was essential for the growth of the animal; that animals deprived of this material grew for a time, but gradually ceased to do so. Later on, Osborne, Mendel, McCollum and Davis discovered a like substance in butter fat; and still later Dr. McCollum found the same growth stimulating material, or one very like it, existing in the leaves of plants. These scientists found, upon investigation, that there were probably two substances in milk—one soluble in the fat, the other in the protein-free and fat-free whey—both of which were essential for normal growth. In 1911 Dr. Funk discovered in rice polishings a substance which he believed to be a cure and preventive of Beri-beri; to this substance, which is now believed to be identical with the second substance found in milk, he gave the name “vitamine.” Dr. Funk’s name “Vitamine” is now accepted to cover a number of substances essential to growth, and for the prevention and cure of certain diseases. To the first two has been added a third member of the vitamine family, which has proved to be a cure and preventive of scurvy. These substances are called—on account of the substances in which they are soluble—“Fat soluble A,” “Water soluble B,” and “Water soluble C.” The table on page [496] shows the sources from which these factors may be obtained. The four plus system is used by Dr. Eddy to describe the abundance with which they occur.[11]
Function of “Fat Soluble A.”—All investigators agree that the “A” vitamine is an essential factor in the growth of young tissue, and the repair of mature tissues. McCollum claims that this vitamine is likewise a factor in the prevention of the eye disease known as xerophthalmia, and other scientists also hold this opinion. Eddy states that a diet lacking in the “A” vitamine will, in the majority of cases, result in stunted growth and the development of the eye disease, and that the appearance of the latter may be taken as a sure indication of the absence or deficiency of this vitamine.
The following diagram shows the effect of adding fat soluble “A” to the diet which was adequate in other respects. This chart represents the growth curve of young rats.[12]
Figure showing the effect upon growth of adding “fat soluble A”
to a diet adequate in all other respects.
Courtesy of Dr. E. V. McCollum.
Mellanby of England believes the “A” vitamine to be a factor in the prevention of rickets. Scientists of America have recently investigated this disease, and Dr. Hess (New York) has found cod liver oil to be a remedy for it. Cod liver oil is known to be rich in “Fat soluble A,” but whether the cure of rickets is due to the presence of this vitamine in the oil, or to a possible fourth vitamine, is still undetermined.
Effect of Heat on the “A” Vitamine.—Heat, as applied in the ordinary methods of cooking, is not believed to exert a great deal of destruction upon the “A” type of vitamine; but hydrogenation, the process used in the hardening of certain fats in the manufacture of lard substitutes, is said to destroy it completely.