Protein requirements in humans

Article Abstract:

Proteins from the diet are required for the synthesis of structural proteins, including those in muscle and skin, and for synthesis of important compounds such as hormones. In the body, proteins are continually being broken down into their constituent amino acids, which are then reassembled as new, different proteins. The general principles used for estimating protein requirements are stated in this paper, which was held for three years before publication so that the official revised Recommended Dietary Allowances could be published first. The component which makes protein different from carbohydrate is nitrogen, and previous estimates of total nitrogen requirements have been flawed. Currently, nitrogen balance studies, which determine the difference between nitrogen intake and excretion, are preferred for assessing adult protein needs. Nine of the twenty amino acids are essential in the diet because they cannot be synthesized by humans. The current knowledge, although incomplete, regarding requirements for these essential amino acids is presented. Certain factors affect the protein value of diets, including digestibility, combinations of amino acids in each meal, and the availability of energy, which is needed for protein metabolism; the contribution of each is reviewed. Protein requirements for various age groups are presented, along with the amounts needed for pregnancy and lactation. Other factors, such as effects of activity, and the effects of high protein intakes, are discussed. These recommendations are compared with those of the previous recommended protein allowances; many of the values are similar, but the methods of calculating the requirements have changed a great deal. (Consumer Summary produced by Reliance Medical Information, Inc.)

Analysis, Nutritional aspects, Protein metabolism, Nutritional requirements, Proteins in human nutrition, Dietary protein

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A theoretical basis for increasing current estimates of the amino acid requirements in adult man, with experimental support

Article Abstract:

The daily requirements of all nutrients have been estimated and published. Requirements vary according to age, gender, and health status. Requirements for the amino acids in healthy adults are examined. Amino acids are the molecular units that combine to make proteins. Adult humans need eight amino acids in the diet, whereas other amino acids required for protein synthesis are manufactured in the body and do not need to be consumed from food. Once the requirement for a nutrient has been published, many nutrition professionals tend to accept this figure. Researchers do from time to time reevaluate the published level and sometimes propose changes. It is suggested that healthy adults need more of each amino acid than the requirement published by the Food and Agriculture Organization/World Health Organization (FAO/WHO). Raising the requirement for the amino acid valine from 10 to 24 mg/kg/day is proposed. For the eight amino acids, the revised level suggested is two to three times the current published level. This represents a substantial increase. If the new higher levels of amino acid requirement are accepted, better protein nutrition would become the goal and food aid programs could be affected. It is acknowledged that the large increases proposed must be viewed as tentative, and need to be confirmed by further research.

Health aspects, Research, World Health Organization, Amino acids, Amino acids in nutrition, Food and Agriculture Organization of the United Nations

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Food energy requirements in humans

Article Abstract:

The energy, or food, requirement of an individual is the number of calories needed to replace energy output, taking into account body size and composition and physical activity. This paper, which was held for publication for three years until official release of the revised Recommended Dietary Allowances, discusses the contribution of various factors to the estimated energy requirements of individuals. The general principles used in determining these estimates are discussed. Components of total energy expenditure include: resting energy expenditure, the amount of calories burned when the body is at rest; thermogenesis, heat production which occurs after eating; and physical activity during work and recreation. The estimated energy allowances for adults, with modifications for pregnancy and lactation, and for infants, children, adolescents, and the elderly, are presented. These estimates of energy requirement are similar to previous recommendations, except that slightly lower values are suggested for children and pregnant women, with slightly higher values for lactating women. It is also stressed that adjustments for individual activity patterns are essential. (Consumer Summary produced by Reliance Medical Information, Inc.)

Reports, Physiological aspects, Energy metabolism

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