NUTRIENT-TO-CALORIE RATIOS IN APPLIED NUTRITION.
This paper discusses the desirability of expressing the nutrient require ments of man and animals relative to their associated energy intake, and proposes a format for expressing a dietary standard for humans. Caloric needs are known to vary with size, activity, and productive performance. There is agreement that most of the nutrients quantitatively considered in diet or ration formulation should remain in balance with each other and with energy, for optimal food efficiency. Many nutri tionists believe that it is not possible to state the requirements for individual nutrients without also specifying the amounts of others also to be ingested. In the case of nutrients that must be stored in the body, as during growth, the ratio to energy intake changes progressively to the final adult equilibrium status. In the case of the human, one adult, and 3 juvenile "diet" categories appear to be adequate, within each of which the interbalances between nutrients and that between nutrients and energy are constant. Within these 4 categories, adequate daily nutrition can be accomplished by adjustments in the intake of the diet as a whole. One of the far-reaching concepts in dietetics and animal rationing is the im portance of balance between the nutrients of the diet â€” the realization that relative excesses are no less undesirable than rela tive deficiencies. We have only begun to unravel the picture of nutrient interrela tionships, but it is abundantly clear that the efficiency of food utilization by the animal body may be markedly affected by alterations in the inter-nutrient balance, or between the nutrient and energy pattern, or both. There may be some doubt whether we yet can define the ideal interrelations, but periodically since 1810 tabulations have been made of the quantities of energy and of nutrients that evidence indicated were needed daily by farm animals accord ing to species, weight, age, sex and produc tion performance. One pertinent study was that by Guilbert and Loosli ( 1) in which they computed for farm animals and poultry from the appro priate feeding standards (NAS-NRC series) the recommended daily feed intakes, and total digestible nutrients (TDN); and per unit TDN, the digestible crude protein, calcium, phosphorus, carotene, vitamin A, vitamin D, thiamine, riboflavin, niacin and pantothenic acid for individuals at at tained weights of from 10 to 100% of expected adult size. Although their study was mostly concerned with immature growing animals, and was hampered by excessive variability partly from the fact that the NAS-NRC feeding standard values at that time contained margins of safety of unknown magnitude over the true require ments, they prepared a table of generalized recommended allowances of protein, Ã‡a,P, thiamine and riboflavin in ratio to TDN intake for farm livestock and poultry. They state, 'The feasibility of expressing (in feeding or dietary standards â€”E.W.C.) the relationship of the various nutrients with metabolizable energy rather than with total digestible nutrients should be ex plored." They also comment, "In the pre occupation of seeking new nutritional fac tors, it would appear desirable to pause when they are found to determine their fundamental relations to other nutrients, to body weight, or to caloric intakes, and the quantitative requirements in a sys tematic procedure." Because of incomplete knowledge, the authors of the early tabulations often claimed as requirements, nutrient values later shown to be excessive; and it is sig nificant that, other than inclusion of addi tional nutrients, the chief changes in the chronologically successive "standards," even though by different authors, have been downward revisions of the amounts of nutrients believed to be required rela tive to energy intake. The criteria for such changes have been: increased effi ciency of the ration in producing growth, fattening, milk or egg production, or deReceivedfor publicationAugust8, 1963. J. NUTRITION, 82: '64 353 D ow naded rom http/academ ic.p.com /jn/article-at/82/3/353/4777993 by gest on 19 M arch 2019
Mathematical analysis of energy-nutrient relationships. 1. Protein and energy.
Abstract THE fact that protein and energy should be related in the diet has long been known as evidenced by the outline for calculation of the “nutrient ratio” (Morrison, 1948). In spite of the fact that the “nutritive ratio” was available, Morrison’s recommendations for poultry were quoted from the publication by the National Research Council, “Recommended Nutrient Allowances for Poultry, 1946.” These recommendations did not mention energy. The first major studies concerning energy values for poultry were published by Fraps (1946). These energy values were termed “productive energy” and defined by Fraps as the “net energy” stored in the body as fat and protein. 2 , 3 Later reports have criticized the use of “productive energy” because of difficulty of determination and the large variance in values found by different investigators for the same feedstuff. Some contend that its determination is impossible, or more precisely that the value obtained is worthless (Titus, 1951; Hill…
The physiology of ski-ing
This paper gives the results of physiological observations on a number of skilled and well-trained skiers, made either on level terrain, or going uphill. It is now clear that it is possible when to take harder physical exercise (as judged by the of than in any other way, perhaps, when