Plasma amino acid response to single test meals in humans. V. Ethiopian preschool children given lowcost protein supplements

Plasma amino acid response to single test meals in humans. II. Healthy young adults given synthetic amino acid mixtures

The postprandial plasma amino acid response to test meals containing different amino acid mixtures was analysed in six young adults. The amount of amino acids given in each test meal was equivalent with 3.5 g of nitrogen. Each test meal also contained a large amount of carbohydrate (mainly as wheat starch). Five different amino acid mixtures were used, and the effects on the plasma amino acid response of different dietary levels of lysine, isoleucine and methionine were studied in detail. The plasma amino acid responses were evaluated both by a modified Longenecker and Hause procedure (PAA ratios) and by the procedure proposed by Graham and Placko (percentage changes in the postprandial essential amino acid molar ratios). The plasma amino acid response of lysine was found to be less sensitive to reductions in the dietary supply than the isoleucine and methionine responses evaluated by these procedures. The influence of altered levels of dietary supply on the postprandial plasma concentrations of isoleucine and methionine seemed to be specifically great at the intake levels where these essential amino acids become limiting for protein utilization according to the amino acid score of the test mixtures. The nutritional significance of the postprandial pattern and level of essential amino acids is discussed on basis of the present results. Experimental conditions and evaluation models are examined with regard to the use of single-meal plasma amino acid responses to assess the protein quality of human diets.

Plasma amino acid response to single test meals in humans. III. Supplementary effect of dried skim milk and L-methionine on a vegetable protein mixture

The plasma amino acid response to single test meals in young adults was used for human biological evaluation of the supplementary effect of dried skim milk powder (DSM) and synthetic L-methionine on a vegetable protein mixture. The protein sources in the vegetable mixture were wheat flour, defatted soya bean flour and pea flour. The plasma amino acid responses were evaluated both as PAA ratios (a modification of the Longenecker and Hause method), and as delta MR% (percentage change in the postprandial essential amino acid molar ratios according to Graham and Placko). Both evaluation methods indicated that there was an adequate supply of all the essential amino acids in the basic vegetable mixture, except for a small deficit of methionine. Supplementation (5% and 10%) with DSM did not significantly improve the low plasma amino acid response of methionine. The addition of synthetic L-methionine proved to be very effective in this respect. 1 g of L-methionine per 100 g of proteins from the vegetable mixture gave a plasma methionine response similar to that of the other essential amino acids. This implies that the deficit of methionine in the basic wheat/soya bean/pea mixture was about 30%.