NEUTRAL AND BASIC-AMINO-ACID CONCENTRATIONS IN PLASMA DURING THE DAY IN SUBJECTS FED WITH 2 MODEL RURAL AND 2 MODEL URBAN MEXICAN DIETS

The purpose of the study was to measure the variation in concentration s of plasma neutral and basic amino acids during the day in subjects f ed two Mexican model rural diets, one containing 55% (R55) and the oth er 70% (R70) of energy as carbohydrates, and two model urban diets wit h the same two proportions of carbohydrates (U55 and U70). The R55 and R70 diets contained 1.35- and 1.69-fold more fiber than the U55 and U 70 diets, respectively. Eight female volunteers were adapted to each o f the four diets for 3 d before the day of blood sampling. Protein and energy intakes were adjusted to each subject for a consumption of 1 g protein/kg body wt and 150.7 kJ/kg body wt. Blood samples were withdr awn at 0700, 0930, 1100, 1500, 1900, 2300, and 0300. Only plasma conce ntrations of alanine changed during the day, dropping significantly (P < 0.05) at 2300 and 0300 with the U70 diet. Urban diets produced sign ificantly higher plasma isoleucine and valine values than did the rura l diets at some sampling times. Plasma phenylalanine was significantly higher with the U70 diet at 2300 than with the other three diets. Ala nine plasma concentrations were significantly higher with the U55 diet at 1900 and significantly lower with the R55 diet at 0930 with respec t to the other diets. Lysine was significantly higher at 0700 with the U70 diet than with the other three diets. No other significant change s were observed. These results show the stability of the plasma amino acid profile despite the consumption of different diets in physiologic proportions. Possibly, some of the changes observed in the plasma ami no acids can be explained by the high proportion of dietary fiber in t he Mexican rural diets.