Postprandial concentration of circulating branched chain amino acids are able to predict the carbohydrate content of the ingested mixed meal.
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BACKGROUND: The amount of the macronutrients protein and carbohydrate (CHO) in a mixed meal is known to affect each other's digestion, absorption, and subsequent metabolism. While the effect of the amount of dietary protein and fat on the glycemic response is well studied, the ability of postprandial plasma amino acid patterns to predict the meal composition is unknown. OBJECTIVE: To study the postprandial plasma amino acid patterns in relation to the protein, CHO, and fat content of different mixed meals and to investigate if these patterns can predict the macronutrient meal composition. DESIGN: Ten older adults were given 9 meals with 3 different levels (low, medium, and high) of protein, CHO, and fat in different combinations, taking the medium content as that of a standardized western meal. We monitored the postprandial plasma response for amino acids, glucose, insulin, and triglycerides for 8h and the areas under the curve (AUC) were subsequently calculated. Multiple regression analysis was performed to determine if amino acid patterns could predict the meal composition. RESULTS: Increasing meal CHO content reduced the postprandial plasma response of several amino acids including all branched chain amino acids(BCAA) (leucine; q<0.0001, isoleucine; q=0.0035, valine; q=0.0022). The plasma BCAA patterns after the meal significantly predicted the meal's CHO content (leucine; p<0.0001, isoleucine; p=0.0003, valine; p=0.0008) along with aspartate (p<0.0001), tyrosine (p<0.0001), methionine (p=0.0159) and phenylalanine (p=0.0332). Plasma citrulline predicted best the fat content of the meal (p=0.0024). CONCLUSIONS: The postprandial plasma BCAA patterns are lower with increasing meal CHO content and are strong predictors of a mixed meal protein and CHO composition, as are plasma citrulline for the fat content. We hypothesize that postprandial plasma amino acid concentrations can be used to predict the meal's macronutrient composition.
