The Effects of Mastication on Energy Release From Walnuts
Condition: Obesity
Study type: Interventional

Summary: 
      With an emphasis on oral processing, this study seeks to characterize the mechanisms that
      account for the high satiation properties of walnuts and low energy yield during digestion.
    

Detailed description: 
      Recent evidence indicates up to 20% of the energy from walnuts is not absorbed. This low bio
      accessibility is comparable to almonds with markedly different physical properties and much
      higher than for pistachios with similar physical characteristics. These counter-intuitive
      findings require mechanistic explanations so they may be accepted and used to formulate
      policy and clinical recommendations. It is proposed that the differences in the structure of
      nuts accounts for the energy yield results. In addition, the whole nut yields superior
      effects on fullness and this leads to focus on oral processing. It may be that the mechanical
      act of chewing generates satiety sensations or it may be that the mechanical disruption of
      the parenchymal call walls releases lipid and protein and their higher concentrations
      activate the release of gut peptides associated with satiety.

      Visit 1: Participants will report the Laboratory of Sensory and Ingestive Studies following
      and overnight fast, and having refrained from using oral care products for at least two hours
      prior to the visit. Participants who meet the BMI requirements, will have electrodes placed
      on their wrist, upper, and lower jaw and will be asked to chew the following stimuli:
      walnuts, almonds and pistachios for 15 seconds and expectorate the bolus into a beaker.
      However, when presented with 5 g walnuts participants will be asked to chew until the point
      where they would normally swallow and then spit the bolus into a beaker. The chewing
      conditions are randomized and include: 1) 5 g nuts alone, 2) 5 g nuts with 5 ml water, 3) 5 g
      nuts with 5 ml apple juice, 4) 5 g nuts with 5 g plain yogurt, 5) 5 g nuts with 5 g sweet
      yogurt. Following each chewing condition, participants will rate hedonic preference on a
      9-point scale.

      Visit 2 and 3: Following an overnight fast, the participant will be placed in a semi-supine
      position and a catheter will be placed in a vein in the antecubital space of one arm. A 9 ml
      baseline blood sample will be collected. Participants will complete a validated appetite
      questionnaire on a palm pilot right after the baseline blood draw. The participants will then
      consume 28 g of walnuts or 28 g walnut butter given in random order. Additional blood samples
      and appetite questionnaire will be taken at 15, 30, 45, 60,120, and 180 minutes. The blood
      will be stored in a minus 80 freezer to be analyzed at a later date for insulin, glucose,
      GLP-1, Ghrelin, and PYY.
    

Intervention name(s): Chewing
Intervention type(s): Other
Intervention description(s): On the first visit, the random nut treatments will include chewing walnuts, almonds and pistachios. The chewing conditions will include: 1) 5 g nuts alone, 2) 5 g nuts with 5 ml water, 3) 5 g nuts with 5 ml apple juice, 4) 5 g nuts with 5 g plain yogurt, 5) 5 g nuts with 5 g sweet yogurt.
On visits 2 and 3 the treatments of either 28 g of walnuts or walnut butter will be presented.
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: energy availability; walnuts