Humans amino acid requirements

Fuller MF, Garlick PJ Human amino acid requirements. Annu RevNutr 1994 14 217. 

Source Values taken from Young VR, Bier DM. A kinetic approach to the determination of human amino acid requirements. Nutr Rev 45 289-298, 1987. 

On the other hand, the methods currently used for measuring protein qnaUty of foods were established when information was not extensively available on human amino acid requirements. Therefore, while results were not grossly in error, they did not accurately reflect human requirements. Since most of these methods nse a rat assay, they in large part measnre the amino acid... 

The nutritive value of a protein depends on its capacity to provide nitrogen and amino acids in adequate amounts to meet the requirements of an organism. Thus, in theory the most logical approach for evaluating protein quality is to compare amino acid content (taking bioavailability into account) of a food with human amino acid requirements. A number of comparisons have been made using reference patterns such as those derived from egg and milk protein. The first major change in procedure was substitution of a provisional pattern of amino acid requirements for the egg protein standard. 

A hypothetical reference protein derived from the pattern of human amino acid requirements was proposed as a standard for comparison. Shortcomings have been recognized and progress has been made in accurately evaluating human amino acid requirements. Equally critical for success is the ability to obtain precise measurements of amino acid content in the protein sources. Finally, to improve on accuracy of scoring procedures, chemically determined amino acid contents may have to be corrected for digestibility or biological availability. 

PDCAAS is based on human amino acid requirements, which makes it more appropriate for humans than a method based on the amino acid needs of animals. 

Numerous and conflicting reports on the protein requirements of the adult are to be found in the literature (23, 64, 65, 66). The use of heterogeneous natural food stuffs in the majority of these studies does not permit a ready estimation of the human amino acid requirements from the nitrogen data. In balance studies in which milk proteins constitute the principal nitrogen component of the diet, it is possible to approximate... 

Young, V., and PeUett, P. 1990. Human amino acid requirements with reference to protein quality. Pages 25-40 in Proc. Int. Conf. on Sorghum Nutritional Quality. Purdue University, USAID, and ICRISAT. West Lafayette, IN. 

Amino acid compositions of the four oilseeds are given in Table 3 along with the amino acid (see Amino ACIDS) requirements for humans suggested by a Joint FAO/WHO/UNU Expert consultation. 

Essential amino acid requirements for humans recommended by FAO/WHO/UNU (21). An essential amino acid is one that caimot be synthesized by... 

Pea.nuts, The proteins of peanuts are low in lysine, threonine, cystine plus methionine, and tryptophan when compared to the amino acid requirements for children but meet the requirements for adults (see Table 3). Peanut flour can be used to increase the nutritive value of cereals such as cornmeal but further improvement is noted by the addition of lysine (71). The trypsin inhibitor content of raw peanuts is about one-fifth that of raw soybeans, but this concentration is sufficient to cause hypertrophy (enlargement) of the pancreas in rats. The inhibitors of peanuts are largely inactivated by moist heat treatment (48). As for cottonseed, peanuts are prone to contamination by aflatoxin. FDA regulations limit aflatoxin levels of peanuts and meals to 100 ppb for breeding beef catde, breeding swine, or poultry 200 ppb for finishing swine 300 ppb for finishing beef catde 20 ppb for immature animals and dairy animals and 20 ppb for humans. 

Plants synthesize all the amino acids they require. They do so using as raw material carbohydrates, which they make during photosynthesis, and nitrogen, derived from nitrate ions absorbed from the soil. Animals cannot synthesize all the amino acids required for their regular living, health, and growth. Those they cannot synthesize, known as the essential amino acids, are acquired from plants and/or animals they consume as food. Human beings, for example, acquire nine essential amino acids from their diet. 

Little attention has been paid to the question of inter-individual differences in amino acid requirements. In the attempts to determine what the human adult requirements for individual essential amino acids are (for maintaining nitrogen equilibrium), studies have been made on individual young men. The following inter-individual ranges... 

Pencharz, P.B. Ball, R.O. (2003) Different approaches to define individual amino acid requirements. Annu. Rev. Nutr. 23, 101-116. Determination of which amino acids are essential in the human diet is not a trivial problem, as this review relates. 

Alanine and Glutamine in the Blood Normal human blood plasma contains all the amino acids required for the synthesis of body proteins, but not in equal concentrations. Alanine and glutamine are present in much higher concentrations than any other amino acids. Suggest why. 

Animal organisms generally require effective assistance of intestinal flora, as in ruminants, to assimilate inorganic nitrogen into body protein. This accounts for the human needs of a daily requirement of 70-80 grams of protein, However, over half of the protein-constituent amino adds can be derived from other amino acids by their own enzymic reactions. Thus, amino acids are classified as essential or nonessential. Amino acid requirements vary with the physiological state of the animal, age. and possibly with the nature of the intestinal flora. 

PER is a method to metabolize or determine the quality of protein in foods. Quality is measured by the amount of usable protein and the growth resulting from it through an animal assay. Formerly, this method was used as the standard method for all protein quality analysis. However, there is some question as to whether or not it is a valid measurement. This is because PER does not account for the differences in amino acid requirements between humans and rats (Seligson and Mackey, 1984), nor does PER account for the protein needed for cell maintenance. Therefore, PER results often overestimate the requirements for some amino acids and underestimate others. Specifically, PER tends to underestimate the protein quality of lysine-deficient proteins such as wheat gluten (Hackler, 1977). 

Figure 24.8. Essential and Nonessential Amino Acids. Some amino acids are nonessential to human beings because they can be biosynthesized in a small number of steps. Those amino acids requiring a large number of steps for their synthesis are essential in the diet because some of the enzymes for these steps have been lost in the course of evolution.

Young, V. R., and El-Khoury, A. (1995). Can amino acid requirements for nutritional maintenance in adult humans be approximated from the amino acid composition of body mixed proteins Proc. Natl. Acad. Sci. U.S.A. 92,300-304. 

Eagle H (1955a) The specific amino acid requirements of a human carcinoma cell (strain HeLa) in tissue culture. Journal of Experimental Medicine 102 37- 8. 

The problem with using plant sources of protein is that they do not provide the proper balance of the amino acids required for human nutrition [70]. Some of the deficient amino acids may be synthesized by the body. But some, the essential amino acids, must be acquired through the diet for proper human nutrition and growth. Commercial production of amino acids has mainly been for animal feed supplementation. However, cereals supplemented with synthetically produced essential amino acids could improve the nutritional value of plant crops to supply the human protein requirement. In this way a proportion of the crops now grown for animal feed could be diverted to human consumption, and more people could be fed from the same area of arable land than would be possible using animal protein. 

Harper, A. E., Human amino acid and nitrogen requirements as the basis for evaluation of nutritional quality of protein, in Food Proteins, Whitaker, J. R. and Tannenbaum, S. R., Eds., Avi Publishing Co., Inc., Westport, 1977, 363-386. 

In 2002, an expert consultation of international amino acid/protein scientists was convened by the United Nations World Health Organization, Food and Agriculture Organization, and University (WHO/FAO/UNU) to evaluate studies to-date and make recommendations for human protein intake (WHO/FAO/UNU Expert Consultation, 2007). That body had previously asked Rand et al. (2003) to prepare a meta-analysis of nitrogen balance studies. The meta-analysis, consisting of 235 individual subjects across 19 studies was used in the 2007 report, along with other research to make these current WHO/FAO/UNU Expert Consultation (2007) recommendations. The amino acid requirements for adults in the previous EAO/WHO/UNU Expert Consultation Report in 1985 (EAO/WHO/UNU Expert Consultation, 1985) had been taken directly from the 1973 EAO/ WHO report (EAO/WHO, 1973). However, since 1985 concern had arisen regarding the previously derived values and that the values for adults were too low (WHO/EAO/UNU Expert Consultation, 2007). 

Millward, D. J. (1999). Meat or wheat for the next millermium The nutritional value of plant-based diets in relation to human amino acid and protein requirements. Proc. Nutr. Soc. 58, 249-260. 

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