The effect of dilution of milk proteins with non-essential amino acids (L-alanine and L-glutamic acid) on nitrogen retention and biological value of the proteins in children.

It is now well recognized that the biological value (BV) of dietary proteins depends
on the content, availability and balance of essential amino acids in them (Block &
Mitchell, 1946; Swaminathan, 1964, 1967; Swaminathan & Daniel, 1968). The FAO/
WHO Expert Group on Protein Requirements (FAO, 1965) suggested that, after the
required pattern of the essential amino acids has been specified, the percentage of the
total nitrogen intake contributed by the essential amino acids must be indicated. They
also stated that ‘there is good reason to believe that in both human milk and egg
proteins, the proportions of essential amino acids are higher than those required for
older children and adults, although the physiological reason for this is not clear’.
Snyderman, Holt, Dancis, Roitman, Boyer & Balis (1962) reported that addition of
glycine or urea to a milk diet providing 1.1 g proteinlkg body-weight brought about
increase in N retention and body-weight of infants. More recently Daniel, Desai,
Venkat Rao, Swaminathan & Parpia (1968) have reported that dilution of milk proteins
with a non-essential amino acid (glutamic acid) brings about a decrease in the protein
efficiency ratio (PER) of the proteins in proportion to the quantity of glutamic acid
added. It was considered desirable to conduct metabolic studies in growing children
to confirm the findings in rats. In the present investigation, the effect of dilution of
milk proteins with a mixture of two non-essential amino acids (NEA), alanine and
glutamic acid, on N retention and BV of the proteins has been studied in children aged
1-11 years.