Upper Limit of Leucine Intake in Adults

Status: Completed
Study State Date: May 2009
Primary Completion Date: Actual February 2010
Study Type: Interventional
Study Design: Allocation: Non-Randomized, Endpoint Classification: Safety Study, Intervention Model: Single Group Assignment, Masking: Single Blind (Subject)
Phase: Phase 1

The Hospital for Sick Children
Information By: The Hospital for Sick Children
Trial Identifier: NCT00972582
Official Title: Determination of the Tolerable Upper Limit of Leucine Intake in Adult Humans

Description:  When dietary amino acid supplements are consumed by humans they are normally in addition to their normal daily requirements. The investigators' laboratory played a leading role in defining the estimated average requirement (EAR) and the recommended dietary intake for the "essential" amino acids (Dietary Reference Intakes 2005). The other important but less well studied component of Dietary Reference Intakes (DRI) is - What is a safe upper limit of intake? The investigators now propose to determine the safe upper limits of the dietary essential amino acids. The recently published DRI (2005) defines the Tolerable Upper Intake Level (UL) as 'the highest average daily nutrient intake level that is likely to pose no risk of adverse health effects to almost all individuals in the general population.' As intake increases above the UL, the potential risk of adverse effects may increase'. In this proposal, the investigators define a novel method to define the safe upper limit where the 'maximum oxidative potential' of an amino acid identifies the 'metabolic limit' to dispose the amino acid. Intakes of amino acid above this level will increase the potential for adverse effects to appear.

+ Additional Objectives Detail

The objective of the study will be to determine the 'metabolic limit' of leucine oxidation in healthy young men by: A) Measuring leucine oxidation in response to short term (8 hr) graded excess leucine intake B) Correlating changes in leucine oxidation with changes in plasma concentrations of keto-isocaproic acid (KIC, the first breakdown product of leucine metabolism), other essential amino acids, ammonia, urea, creatinine, glucose, insulin, and electrolytes (sodium, potassium, chloride) to identify potential biomarkers C) Correlating changes in leucine oxidation with changes in urinary excretion of leucine and ketoisocaproic acid (KIC), urea and creatinine to identify potential biomarkers

Accepts Healthy Volunteers?: Accepts Healthy Volunteers
Enrollment: 5 Actual
Minimum Age: 18 Years
Maximum Age: 35 Years
Gender(s): Male
Additional Criteria:  Inclusion Criteria: - Male - 18-35 years old Exclusion Criteria: - Report a recent history of sudden weight loss - Have unusual dietary habits such as chronic consumption of caffeinated beverages or alcohol - Have any endocrine disorders - Are currently using any prescribed medications

Dietary Supplement: Leucine Increase
Primary Outcome Measures:
Breath carbon dioxide production
Time Frame: Study Visits 1-7 (-45min,-30min,-15min, +2.5hrs, +3hrs, +3.5Hrs +4hrs)
Safety Issue: No

Secondary Outcome Measures:
Time Frame: Study Visits 1-7 (Hourly)
Safety Issue: No

Time Frame: Study Visits 1-7 (8hr timepoint)
Safety Issue: No

Time Frame: Study Visits 1-7 (after 5hr meal)
Safety Issue: No

Patient Groups:
Assigned Interventions:

Leucine: Experimental
Dietary Supplement: Leucine Increase
Graded stepwise increases in leucine intakes (50, 250, 500, 750, 1000, 1250 and 1500mg/kg/day)


Principal Investigator: Paul B Pencharz, MD, The Hospital for Sick Children, Toronto, Canada

Study Locations:
+ Show All 1 Study Locations

The Hospital for Sick Children 
Toronto, Canada

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