Leucine Requirements in School-Age Children

Determination of Leucine Requirements in Healthy School-Age Children Using the Indicator Amino Acid Oxidation Method

Leucine is an essential amino acid, which serves a special purpose of signaling cell growth in muscle in addition to making up protein. Essential amino acids like leucine need to be eaten every day from our foods like meat, dairy, eggs, beans, and nuts, as they cannot be made by our bodies. The current recommendation for leucine in the diet of school-age children are based upon adult needs. This study will measure the leucine requirement in children aged 6-10 years old using an non-invasive technique with special diets, safe stable isotopes, and simple breath collections. Creating guidelines based on measured requirements for leucine in this age group is essential for supporting optimal growth in healthy children.

Study Overview

• Status: Not yet recruiting
• Conditions: Nutrient Intake
• Intervention / Treatment: Dietary supplement: Leucine Intake

Detailed Description

Purpose:

- The purpose of this study is to determine the requirement of the essential amino acid leucine, in school-aged children (6-10 years old), with the minimally invasive indicator amino acid oxidation (IAAO) protocol.

Hypothesis:

- The leucine requirement for healthy school-age children is higher than current 2005 recommendation of 40-49 mg/kg/d when measured using the IAAO method.

Justification:

- Protein is essential for growth, tissue repair, and maintenance of physiological functions throughout the lifecycle. Dietary protein is particularly important during childhood to support a healthy growth trajectory and lean body mass development. Despite the importance of protein to support early life growth and development, childhood protein requirements are largely extrapolated from adult values, and not on pediatric-specific data. Consequently, the current leucine recommendations for children of 40-49 mg/kg/d may not accurately reflect the physiological needs of growth.

Objectives:

• Primary Objective: To determine the leucine requirement in healthy school-aged children using IAAO.
• Secondary Objective: To quantify urinary flux of L-[1-13C] phenylalanine as an additional measure of amino acid metabolism during the experimental protocol.

Research Design:

• Randomized crossover metabolic design based on the IAAO technique to estimate the minimum dietary requirement for leucine. The repeated measures study design involves 7 children (participants) completing 1 pre-study visit and 5 IAAO study visits each with a randomized leucine intake.
• After a 10h fast, each child (participant) is randomized to receive 1 of 7 leucine intake levels (10, 20, 30, 40, 50, 60 or 80 mg/kg/d). On the study day, the diet is administered hourly as eight isonitrogenous, isocaloric meals. Each meal consists of two protein-free cookies and a formulated drink prepared with crystalline amino acids, a flavoured protein-free liquid (powdered drink mix), and corn oil. Multivitamin supplements are provided throughout the study to ensure adequate micronutrient intake. The study diet provides an energy intake equivalent to 1.7 x resting energy expenditure and 1.5 g/kg protein.
• The principle underlying IAAO is that when the intake of an essential amino acid is insufficient, protein synthesis cannot proceed, and the remaining amino acids, unable to be stored, are oxidized. This physiological process can be leveraged by administering a stable isotope-labeled "indicator" amino acid, L-[1-13C]-phenylalanine. When requirements are met, the indicator is incorporated into body protein, but when an amino acid is limiting, the indicator is oxidized, and its labeled carbon appears as 13CO2 in the breath.

• Study Type: Interventional
• Enrollment (Estimated): 7
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Kendall Plant; Phone Number: 4607 604-875-2000; Email: kendall.plant@bcchr.ca
• Study Contact Backup: Name: Rajavel Elango; Phone Number: 4911 604-875-2000; Email: relango@bcchr.ubc.ca

Study Locations

• Canada
  • British Columbia
    • Vancouver, British Columbia, Canada, V5Z 4H4
      • BC Children's Hospital Research Institute
      • Principal Investigator: Rajavel Elango

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Healthy children
• Aged 6 to 10 years at enrollment
• Body weight between the 3rd and 85th percentile according to WHO Child Growth Standards
• Assent from the child and written informed consent from parent(s) and/or legal guardian(s)

Exclusion Criteria:

• Diagnosis of any acute or chronic medical condition
• Current use of prescription medication that may affect protein or energy metabolism
• Recent weight loss
• Recent illness (fever, vomiting, severe runny nose within the past 5 days)
• Inability to comply with study procedures

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: Test Leucine Intakes; Randomized to receive 1 of 7 leucine intake levels (10, 20, 30, 40, 50, 60 or 80 mg/kg/d). Participants will complete up to 5 test intake allocations.

Dietary supplement: Leucine Intake; Participants consume 8 hourly meals that contain the assigned test leucine intake. Each meal will provide one-twelfth of the participants' daily energy requirements as estimated by 1.7 x Resting Energy Expenditure (REE) and adequate protein at 1.5 g/kg/d, to maintain a metabolic steady state. The meals are in the form of a crystalline amino acid protein shake, and protein-free cookies.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Carbon-13 Oxidation	9 breath samples will be collected during the study day, to measure the rate of oxidation of tracer phenylalanine in the expired breath.	8 hours (1 study day)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Urinary L-[1-13C] Phenylalanine Flux	3 urine samples will be collected during the study day to measure urinary excretion of phenylalanine	8 hours (1 study day)

Collaborators and Investigators

• Sponsor: University of British Columbia
• Investigators: Principal Investigator: Rajavel Elango, University of British Columbia

Study record dates

Study Major Dates

• Study Start (Estimated): May 1, 2026
• Primary Completion (Estimated): April 1, 2027
• Study Completion (Estimated): December 31, 2027

Study Registration Dates

• First Submitted: March 19, 2026
• First Submitted That Met QC Criteria: March 19, 2026
• First Posted (Actual): March 25, 2026

Study Record Updates

• Last Update Posted (Actual): March 25, 2026
• Last Update Submitted That Met QC Criteria: March 19, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: Leucine; Isotope; Amino Acid; School-Age Children
• Other Study ID Numbers: H26-00055

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: There is no plan to share data with other researchers

Drug and device information, study documents

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