Phenylalanine Requirements in Healthy Pregnant Women
Condition: Pregnancy
Study type: Interventional

Summary: 
      Phenylalanine is an essential amino acid that people need to obtain in their diets. Amino
      acids are the building blocks for protein, which is required to form tissues in the body. It
      is well known that pregnant women require more protein in their diets, but the exact amount
      for each amino acid is undetermined. To find out how much of phenylalanine pregnant women
      require, the investigators plan to study pregnant women in early and late gestation with a
      modern minimally invasive technique.
    

Detailed description: 
      The investigator's purpose is to determine the phenylalanine requirements in healthy pregnant
      women as part of a Master's Thesis project. The determined requirements can be taken into
      account when giving dietary recommendations, to ensure healthy pregnancies. The hypothesis is
      that the current recommendations for phenylalanine intake given to pregnant women are
      underestimated. The investigators also hypothesize that the phenylalanine requirements at
      early stages of pregnancy will be lower than the requirements towards the later stages of
      pregnancy.

      Current dietary intake recommendations for phenylalanine are based on factorial
      (mathematical) calculations and do not account for requirement differences between early and
      late pregnancy. Static recommendations throughout all stages of pregnancy are not appropriate
      because of the multitude of adaptations the human body goes through during gestation. Whether
      phenylalanine requirements differ between different stages of gestation is unknown. In
      addition, phenylalanine is the precursor for tyrosine, which is a conditionally indispensable
      amino acid. Together they are referred to as the aromatic amino acids. The DRI gives a
      recommendation for total aromatic amino acids (TAA, phenylalanine + tyrosine) of 36 mg/kg/d
      during pregnancy. Since this study is the first interested in phenylalanine requirements
      during pregnancy, the investigators will determine the phenylalanine requirements in the
      presence of excess tyrosine (61 mg/kg/d) during pregnancy, similar to earlier studies.

      The investigators will recruit healthy pregnant women aged 20 to 40 in their 13th-19th week
      of gestation or 33rd to 39th week of gestation. Once they get in contact with the lab, an
      initial visit (pre-study) will take place. Here, the participants will be measured for their
      eligibility and taken through the consent form. They have to participate in a pre-study for
      each stage of pregnancy, if they wish to participate in both stages. If they meet all the
      criteria and agree to participate, they will return for up to two study days per stage of 8
      hours each. Therefore, if they are recruited during late pregnancy they are only able to
      participate in two study days in total. During these study days they will be fed protein
      shakes containing the stable isotope, and then oxidation of this isotope will be measured to
      determine a breakpoint (requirement) of phenylalanine. Breath samples, urine samples, and a
      small blood sample will be taken during the study day.
    

Intervention name(s): Phenylalanine intake
Intervention type(s): Dietary Supplement
Intervention description(s): Oral consumption of eight hourly experimental meals- Includes 4 tracer-free experimental meals containing a mixture of free amino acids, calories from a flavored liquid and protein free cookies and 4- labeled amino acid experimental meals.
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: Phenylalanine; Direct Amino Acid Oxidation; Stable isotopes