Dietary protein requirement of 65–75 year old females using indicator amino acid oxidation (IAAO) technique

Abstract

Studies of dietary protein requirement in vulnerable groups, including elderly adults, are needed using methods other than nitrogen balance. The objective of this study was to determine the protein requirement in 8 healthy free‐living elderly females (65 – 75y old) by measuring the oxidation of L‐[1‐13C]‐phenylalanine to 13CO2 in response to graded intakes of protein. Subjects received a maximum of 7 protein intakes (0.2 to 2.0g.kg−1.d−1) for a total of 43 studies (preliminary data). The diets provided energy at 1.7 times measured resting energy expenditure and were isocaloric. Protein was given as an amino acid mixture patterned after egg protein. All subjects consumed controlled diets containing 1 g protein.kg−1.d−1 for 2 days prior to the study day. The mean protein requirement was determined by applying a 2‐phase linear regression crossover analysis on F13CO2 (label tracer oxidation in 13CO2), which identified a breakpoint in the F13CO2 in response to graded intakes of protein. Mean protein requirement was determined to be 1.1 g.kg−1.d−1. These preliminary results suggest the mean protein requirement of elderly women is higher than current recommendation derived from nitrogen balance studies. This study was supported by a CIHR grant.