Influence of Habitual Protein Intake on AA Tracer Oxidation (HPI)

Impact of Habitual Protein Intake on Estimates of Dietary Protein Requirements in Resistance Trained Athletes

Protein is an essential nutrient that one's diet to maintain important bodily functions and to recover from exercise. Currently, the Indicator Amino Acid Oxidation method (IAAO) has been used to determine protein requirements in a variety of populations including children, neonates, the elderly and recently, resistance trained populations. This study serves to test the robustness of the IAAO method and to determine if high habitual dietary protein intake, as seen in resistance trained males, has the potential to influence the protein requirements determined by the IAAO method. Further, the current study also aims to determine how the body metabolizes or uses dietary protein and how it might change when consuming a protein intake that is less than what is habitually consumed.

Study Overview

• Status: Completed
• Conditions: Protein/Amino Acid Metabolism; Indicator Amino Acid Oxidation Method
• Intervention / Treatment: Other: Three day Controlled Diet; Other: Dietary protein intake reduction

Detailed Description

This study employed a two-phase randomized crossover design, where participants performed both a High/Habitual protein phase and a moderate protein phase. The Habitual protein phase is designed to model resistance trained individual's habitual protein consumption by providing 2.2g/kg/d in a controlled diet. The Moderate protein phase is designed to investigate the impact of decreasing dietary protein intake to a moderate amount (1.2g/kg/d) over five days on protein metabolism. Both phases used the stable isotope L-[1-13C]Phenylalanine and metabolic trails were modelled after the indicator amino acid oxidation (IAAO) technique.

High Protein Phase The high protein phase is three days in length, with diet-controlled throughout, and a metabolic trail on day 3. Participants will perform whole-body resistance exercise on days one and three.

Moderate protein phase The Moderate protein phase is seven days in length, with MT on days three, five and seven. Dietary intake will be controlled throughout the whole phase providing either 2.2 g/kg/d of protein (days one and two), or 1.2 g/kg/d (days three through seven). Full body resistance exercise will be performed performed on days one, three, five and seven.

This phase will allow measurement of protein metabolism over five days following a decrease in dietary protein intake, and to determine the effect of dietary changes on the IAAO method.

• Study Type: Interventional
• Enrollment (Actual): 5
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Canada
  • Ontario
    • Toronto, Ontario, Canada, M5S 2C9
      • Goldring Centre for High Performance Sport

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 35 years (Adult)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: Male

Description

Inclusion Criteria:

• Healthy, weight-trained individuals that have trained consistently for > 1 year
• Habitually dietary protein consumption of 1.9 to 3.0g/kg/d
• Train each muscle group (i.e. chest, back, legs) at least twice a week
• Body mass stable in the last month

• Meets strength relative-to-weight guidelines (adapted from Morton et al., 2016; Chilibeck et -al., 1997)

  • Bench Press: - Bodyweight (kg) * 1.25
  • Leg Press: - Bodyweight (kg) *4.0

Exclusion Criteria:

• Inability to meet health and PA guidelines according to the PAR-Q+
• Inability to adhere to any of the protocol guidelines (e.g. alcohol and caffeine consumption)
• Regular tobacco use, screened by questionnaire

• Illicit drug use (e.g. growth hormone, testosterone, etc.), screened by a survey in training log

  • 1 month sedentary in the last 6 months prior to study participation
  • 30 minutes of continuous cardio per exercise session
• BMI > or equal to 35
• Individual plans to increase or decrease body mass in the next 3 months
• Use of supplements (excluding whey protein), such as creatine and beta-alanine, in the last 30 days

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Other: Habitual Protein phase; A trial investigating protein oxidation/metabolism that was used to model resistance trained individual's habitual dietary protein intake (2.2g/kg/d).	Other: Three day Controlled Diet; Three days of a controlled diet providing 2.2g/kg/d of dietary protein with protein metabolism measured on day 3. This was used to model the habitual intake of this cohort.
Experimental: Moderate Protein Phase; A series of three trials over a one week period investigating protein oxidation/metabolism that was used to investigate the metabolic response of decreased protein intake (1.2g/kg/d) over a period of five days (trials on days 1, 3, 5 following reduction in protein intake from 2.2g/kg/d to 1.2g/kg/d) relative to the Habitual protein phase trial.	Other: Dietary protein intake reduction; Following two days of controlled diet at 2.2g/kg/d of dietary protein, intake was reduced to 1.2g/kg/d for five days, and protein metabolism was measured on days 1, 3, and 5.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Phenylalanine excretion (F13CO2)	Expressed as µmol/kg/h; phenylalanine excretion is determined via breath enrichment (F13CO2) of the oral tracer. Breath 13CO2 enrichment was measured by continuous-flow isotope ratio mass spectrometry	Through study completion, an average of 3 months
Phenylalanine oxidation (PheOX)	Expressed as µmol/kg/h; phenylalanine excretion is determined via breath and urine enrichment of the oral tracer. Breath 13CO2 enrichment was measured by continuous-flow isotope ratio mass spectrometry and urinary L-[1-13C] phenylalanine was measured by liquid chromatography tandem mass spectrometry	Through study completion, an average of 3 months

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Phenylalanine Rate of Appearance (PheRa/Flux)	In µmol/kg/h; phenylalanine rate of appearance is determined via urinary enrichment of the oral tracer by liquid chromatography tandem mass spectrometry.	Through study completion, an average of 3 months
Net Protein Balance	In µmol/kg/h; calculated as the difference between whole-body protein synthesis and protein breakdown. ). Breath 13CO2 enrichment was measured by continuous-flow isotope ratio mass spectrometry and urinary L-[1-13C] phenylalanine was measured by liquid chromatography tandem mass spectrometry.	Through study completion, an average of 3 months

Collaborators and Investigators

• Sponsor: University of Toronto

Publications and helpful links

General Publications

• Tinline-Goodfellow CT, West DWD, Malowany JM, Gillen JB, Moore DR. An Acute Reduction in Habitual Protein Intake Attenuates Post Exercise Anabolism and May Bias Oxidation-Derived Protein Requirements in Resistance Trained Men. Front Nutr. 2020 Apr 22;7:55. doi: 10.3389/fnut.2020.00055. eCollection 2020.

Study record dates

Study Major Dates

• Study Start (Actual): November 1, 2017
• Primary Completion (Actual): April 18, 2018
• Study Completion (Actual): April 18, 2018

Study Registration Dates

• First Submitted: February 13, 2019
• First Submitted That Met QC Criteria: February 14, 2019
• First Posted (Actual): February 19, 2019

Study Record Updates

• Last Update Posted (Actual): February 19, 2019
• Last Update Submitted That Met QC Criteria: February 14, 2019
• Last Verified: February 1, 2019

More Information

Terms related to this study

• Keywords: metabolism; Protein; Amino acids; IAAO; Resistance trained; Tracer; Indicator amino acid
• Other Study ID Numbers: HPI

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No