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
Human energy expenditure.
HYSIOLOGICAL STUDY of man's food needs and capacity for physical work began on a systematic basis about seventy years ago. Following upon Atwater's classic experiments with a human calorimeter at the end of the last century, the validity of using rates of oxygen consumption as the basis for measuring energy expenditure (indirect calorimetry) was firmly established. Throughout this early period rates of energy expenditure during a variety of human activities were recorded. Recently there has been a renewal of interest in such measurements. This is in part due to the development of apparatus which can be conveniently applied under many industrial conditions, where it had not hitherto been practicable to use the more cumbersome apparatus designed for laboratory studies. Also, methods of work in many industries and in agriculture have changed markedly. Machines increasingly do the work formerly done by manual labor. This change is more noticeable in the highly industrialized coun.tries, but it is spreading throughout the world. Much of 'heavy' industry now consists in controlling large sources of mechanical power by means of levers and switches and the work for the human operator is often 'light.' Further, with increased productiveness there has been a shortening of the working week. There is now time and opportunity for recreations on a scale altogether different from fifty years ago. Many recreations demand much expenditure of physical energy and a wage earner may use his muscles more in his leisure time than during his earning hours. These factors call for new assessments of human energy expenditure , Indirect calorimetry enables the energy expended to be determined while a de& nite activity is undertaken for a limited period of time, usually measured in minutes. More information is necessa.ry to assess the energy expenditure in daily life. This energy has, of course, to be provided by the food, if health and activity are to be maintained. In the past most assessments of total energy needs have been made from dietary studies. This was the method used by Voit, Atwater and others, who first stated the energy expenditure of a variety of occupations, after analyzing records of the diets consumed by persons of known employment. The method is open to the theoretical objection that it assumes that the diets consumed provide exactly enough energy with no surplus or deficiency. It provides no direct yardstick of requirement. Indeed in the East and elsewhere large numbers of …
The Lunar Rocks
Book on lunar rocks covering pre-Apollo lunar scientific knowledge, Apollo and future lunar mission planning, lunar mineralogy, petrology and geochemistry, etc