Studies on the Inorganic Constituents of Milk

Abstract

In discussions of the composition of human milk and of modifications of cow's milk, much stress is laid on the absolute and relative proportions of fats, carbohydrates and protein, but, as a rule, no mention is made of the concentration of the mineral constituents. As an example, we may cite the fact that in many clinics the most premature infant is given mixtures of whey, which may provide certain advantages in regard to the quality of the protein, but which contain 300 per cent. more chlorids than does human milk. A similar relation exists in connection with several of the other inorganic constituents.This practice is, of course, based on the assumption that an excess of inorganic material is present even in human milk, and that this excess is not injurious, an assumption not based on experimental evidence. Theoretically, it is, of course, perfectly conceivable that such an excess of salts may not only increase the work of the kidneys to a dangerous degree, but may even induce intestinal disturbances. Stimulated by recent work which has demonstrated the importance of the mineral elements of the diet, we began about one year ago a study of the mineral constituents of human milk and of the various modifications of cow's milk ordinarily used in infant feeding. In this paper, which is the first of a series dealing with this subject, we shall consider only findings on the chlorids of human milk. METHOD OF ANALYSISBefore attempting the collection of data, it was first necessary to find an analytical method by means of which it would be possible to obtain accurate results with a moderate outlay of time, and with relatively small amounts of material. Most of the milk chlorid deter¬ minations recorded in the literature were made either by gravimetric methods, usually from the weight of silver chlorid, or by the Volhard titration. In either case, a considerable volume of milk had to be evaporated to dryness, ashed in a platinum dish at low heat with the

The Electrical Conductivity and Chloride Content of Women's Milk: Part 2: The Effect of Factors Relating to Lactation

“…Hence, it may be concluded that the tendency for after-milk to have higher electrical conductivity and chloride values than fore-milk is a real one. Similar observations were made by Sisson and Denis (1921), Macy, Nims, Brown, andHunscher (1931) and Ishii (1937), but their results were not statistically analysed.These authors were agreed that the values for after-milk could be either greater or smaller than those for fore-milk. Thus, when making investigations into either the electrical conductivity or chloride content of milk, all milk samples should be taken either before a breast-feed or after a breastfeed, unless the daily milk yield can be obtained for examination.…”

“…Hence, it may be concluded that the tendency for after-milk to have higher electrical conductivity and chloride values than fore-milk is a real one. Similar observations were made by Sisson and Denis (1921), Macy, Nims, Brown, andHunscher (1931) and Ishii (1937), but their results were not statistically analysed.…”

“…Previous investigators, who have recorded chloride values for milk specimens taken throughout the day, fail to agree on the time of day when the highest values are obtained (Sisson and Denis, 1921;Macy et al, 1931;and Ishii, 1937). (24) * The number of observations from which each mean has been calculated is indicated by the figure in brackets.…”

The Electrical Conductivity and Chloride Content of Women's Milk: Part 3: Relationship to Adequacy of Lactation

“…Some of the results suggest a relationship between the chloride content of the milk and either the adequacy of lactation or the milk yield, the chloride values below 50 mg. % being usually associated with adequate and those above 50 mg. % with inadequate lactation (Holt, Courtney, and Fales, 1915;Sisson and Denis, 1921;Widdows, Lowenfeld, Bond, Shiskin, and Taylor, 1935;Nozaki, 1934;Ishii, 1937). It has been shown in Part IL that there is not only a relationship between the chloride content of milk and adequacy of lactation, but also a relationship between the electrical conductivity of milk and adequacy of lactation, the average values for both being lower in women with adequate than in those with inadequate lactation.…”

“…In such cases, the infants should be test-weighed. Discussion In the past it has been shown that women between the second week and the fifth month of lactation and with a milk chloride content of less than 50 mg. % usually lactated adequately but those with a milk chloride of more than 50 mg. % usually lactated inadequately (Sisson and Denis, 1921;Nozaki, 1934;Widdows et al, 1935;Ishii, 1937). The chloride level of 50 mg. % quoted by previous investigators is analogous to the five critical levels selected in the present investigation.…”