Pattern of amino acid requirements in humans: an interspecies comparison using published amino acid requirement recommendations.

We undertook an interspecies comparison of essential (indispensable) amino acid requirements, in relation to those for total protein, to examine whether the current, internationally proposed human amino acid requirement patterns are significantly different from those of other animals. Data were compiled in their original form and then expressed as mg amino acid/g total dietary protein (N X 6.25) required (amino acid requirement pattern). Patterns of requirements within the various species were organized according to four, arbitrary age-developmental groupings (very young, early growth, growth and mature), and these were compared with the requirements for (a) human infants, (b) 2-5 year old children, (c) 10-12 year old children and (c) adults, respectively. Statistical comparisons determined if significant differences existed between humans and other species, at apparently similar age-development stages, for both the total and for individual indispensable amino acids. The sum of the specific indispensable amino acid requirements for humans was significantly different than that for other species at infancy, growth and adulthood; the greatest differences, however, were for the amino acid requirement pattern in adulthood. The change between the very young and adult was the greatest for humans. Some of this difference might be due to experimental factors, including the biological status of a species within the arbitrary groupings described and the criteria used to determine "requirements." Nevertheless, it is difficult to escape the conclusion that the current international human amino acid requirements, for adults in particular, appear to be anomalous when judged against data for other animal species.