Introduction to Human Nutrition

Nutrition and Metabolism of Proteins 71

food proteins mentioned above it is not surprising that
there are distinct differences in the intakes of the indis-
pensable amino acids by different population groups
worldwide. An example of such differences is given in
Table 4.16. As already noted, the four amino acids of
greatest importance and those most likely to be most
limiting in intake, relative to requirements, are lysine,
the sulfur amino acids (methionine and cystine), tryp-
tophan, and threonine.

4.8 Factors other than diet affecting
protein and amino acid requirements

Not everyone of the same age, body build, and gender
has the same nutrient requirements. These differences
may be due, in part, to variations in genetic back-

ground. Various environmental, physiological, psy-

chological, and pathological infl uences affect the vari-

ability in physiological requirements for nutrients

among individuals (Table 4.17). For example, as

already discussed, the growing infant or child requires

higher nutrient intakes per unit of body weight than

does the adult. Besides energy, for which the daily

requirement declines with age because of reduced

physical activity, it appears that the nutrient needs of

healthy aged subjects do not differ signifi cantly from

those of young adults. Nevertheless, a characteristic

of aging is an increased incidence of disease and mor-

bidity, which is likely to be far more important than

age per se in determining practical differences between

the nutrient requirements of younger adults and

elderly people.

Table 4.16 Calculated mean values per caput for the availability of specifi c indispensable amino

acids in developed and developing regions

Region

Amino acid per day (mg) mg/g protein

Lys SAA Try Thr Lys SAA Try Thr

Developinga 2947 2160 693 2204 49 36 11 37

Developed and transitionalb 6149 3619 1177 3799 64 38 12 40

From Young VR, Scrimshaw NS, Pellett PL. Signifi cance of dietary protein source in human nutri-

tion: Animal and/or plant proteins? In: Waterlow JC, Armstrong DG, Fowder L, Riley, eds. Feeding

a World Population of More Than Eight Billion People. Oxford University Press in association with

the Rank Prize Funds, Oxford, 1998: 212.

a Data for 61 countries.

b Data for 29 countries.

SAA, sulfur amino acids; TSAA, total sulfur amino acids.

Table 4.15 Protein supplies per caput per day for selected regions

Plant protein Animal protein Cereal protein

Region Total (g) % Total (g) % Total (g) % Total protein (g)

World 26 36 46 64 33 46 72

Developing regions

Africa 11 20 46 80 31 54 58

Asia 16 25 49 75 36 56 65

Latin America 32 45 39 55 25 36 70

Developed regions

North America 72 64 41 36 25 22 113

Western Europe 62 60 41 40 25 24 103

Oceania 71 69 32 31 19 19 102

From Young VR, Scrimshaw NS, Pellett PL. Signifi cance of dietary protein source in human nutri-

tion: Animal and/or plant proteins? In: Waterlow JC, Armstrong DG, Fowder L, Riley, eds. Feeding

a World Population of More Than Eight Billion People. Oxford University Press in association with

the Rank Prize Funds, Oxford, 1998: 212.