Sulphur Amino Acid Requirements in Adults >60 Years
Condition: Healthy
Study type: Interventional

Summary: 
      This study aims to determine the requirements for the sulphur amino acids in adults over the
      age of 60 years:

        1. the total sulphur amino acid requirement as methionine only. Methionine is an essential
           amino acid.

        2. the minimum methionine requirement as methionine in the presence of excess dietary
           cysteine.

      It is known that protein and amino acid metabolism may be altered with age and methionine and
      cysteine, in particular, may be important in the diet of older adults.

      Up to 7 different levels of methionine intake as methionine only (no dietary cysteine) and up
      to 7 different levels of methionine intake in the presence of excess dietary cysteine will be
      tested in each subject in random order. Each level of intake will involve a 3-day maintenance
      diet, with measures being collected on the third.
    

Detailed description: 
      The sulphur amino acids (SAA) are methionine and cysteine. Methionine is essential and must
      be obtained from the diet whereas cysteine is considered non-essential and is synthesized
      from methionine. They have many other important roles that are secondary to their role in
      protein building. For example, they are needed to make the antioxidant glutathione (GSH),
      which protects the body's cells from damage. However, protein and GSH metabolism have been
      shown to change with age and hence, the SAA requirements may also be changed. Despite this,
      current SAA requirements are based on studies conducted in young adults. Thus, there is a
      need to determine the SAA requirements directly in older adults.

      The purpose of the study is to apply the minimally invasive indicator amino acid oxidation
      (IAAO) protocol to determine the SAA requirements in healthy adults over 60 years of age. The
      requirements will be determined as (1) the total sulphur amino acid requirement as methionine
      only and (2) the minimum methionine requirement by providing methionine in the presence of
      excess dietary cysteine.

      A pre-study assessment will be conducted to assess health status using: medical history and a
      physical exam; and a blood draw (10mL) for fasting blood glucose and hemoglobin A1c to test
      for diabetes, vitamin B and folate concentrations, and urea and creatinine to test renal
      function.

      In order to determine the requirements, each participant will be studied at up to 7 varying
      intakes levels of methionine in random order. Each intake level will be studied over 3-days:
      two adaptation days (day 1 and 2) and one study day (day 3). On the adaptation days,
      participants will be provided with a milkshake diet providing all the protein and nutrients
      they need. Participants will consume 4 meals/day in their usual home environment. On the 3rd
      day participants will come to the Clinical Research Centre at SickKids where they will be
      given hourly meals and breath and urine samples at specified times.A blood sample will also
      be collected for analysis of serum insulin, glucose and secondary parameters (i.e.
      concentrations of amino acids, glutathione, homocysteine and CRP). The mean (estimate average
      requirement) total sulphur amino acid requirement and minimum methionine requirement will be
      calculated with breakpoint analysis using a two-phase linear regression crossover analysis.
    

Intervention name(s): Sulphur amino acids
Intervention type(s): Other
Intervention description(s): For the total sulphur amino acid requirement, there are 7 different methionine test levels (without dietary cysteine) ranging from 5 to 40 mg of methionine per kilogram body weight per day.
For the minimum methionine requirement, there are 7 different methionine test levels (with excess dietary cysteine).
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Other
Keywords: elderly; amino acid requirement; methionine; cysteine; dietary requirement; sulphur amino acids