Gastric Emptying After Bread Consumption
Condition: Gastric Emptying
Study type: Interventional

Summary: 
      The rate of gastric emptying is proposed to be one of the major determinants of postprandial
      glycemia. A slower gastric emptying will thus result in a less pronounced rise in blood
      glucose, which is especially desirable in diabetes care as it will highly influence the
      overall glycemic control. The present study aims to investigate the rate of gastric emptying
      and postprandial blood glucose levels in response to the intake of bread with different
      dietary fiber-content. Though bread is one of the major sources of dietary carbohydrates in
      Central- and Northern Europe, the mechanism and the metabolic effects of bread consumption,
      however, is investigated in a limited number of studies.
    

Detailed description: 
      The rate of gastric emptying is related to small intestinal motility and absorption of
      carbohydrates, and it is one of the major determinants of postprandial glycemia. A slower
      rate of gastric emptying will thus result in a less pronounced rise in blood glucose.
      Especially in diabetes care, reduced gastric emptying is desirable because of its effect on
      the rise of postprandial blood glucose, which again highly influences the overall glycemic
      control.

      Bread is one of the most eaten food items in Central- and Northern Europe, being one of the
      major sources of dietary carbohydrate intake. In addition, bread often contains a diverse
      range of dietary fiber. The effect on gastric emptying and the amount of dietary
      carbohydrates absorbed in the small intestine depends on the overall meal composition, the
      degree of processing, and the type of dietary fiber, e.g., viscous or non-viscous. The
      oat-derived dietary fiber beta-glucan may have favorable properties in this regard as adding
      beta-glucan to a meal has been shown to slow down the rate of gastric emptying. However,
      studies investigating the effect of beta-glucan on gastric emptying are scarce.

      For assessment of gastric emptying, scintigraphy is seen as the "gold standard" as the method
      readily can discriminate between gastric emptying and absorption of glucose in the small
      intestine. However, this method is not often used due to its invasive nature and radiation.
      High-resolution real-time ultrasonography is now the most preferred method and regarded as a
      new "gold standard", proving good inter- and intra-observer agreement. Compared to
      scintigraphy, ultrasound is a safe and non-invasive procedure widely available in clinical
      settings.

      Objectives

      To establish whether a wheat bread with an optimized content of beta-glucan has a different
      effect on gastric emptying, satiety, and postprandial glycemia compared to control bread.

      Study procedures

      Recruitment

      Healthy adults (age range 18 to 40 years) with normal to overweight body mass index (BMI:
      18.5-30 kg/m2) and no gastrointestinal diseases or other issues that can affect gastric
      motility, are eligible and will be asked to participate. Health status will be briefly
      checked during a screening examination.

      Participants will be recruited through flyers, announcements, and advertisements in social
      media, such as Facebook. The eligibility of participants will be addressed during a screening
      visit. Participants will answer questionnaires including questions on general health status,
      lifestyle habits, current medications, allergies, and gastrointestinal symptoms (using the
      ROMA-IV questionnaire).

      Study design: randomized cross-over design

      The study will be conducted at the Research Unit for Health Surveys, University of Bergen, on
      non-consecutive days, with at least 3 days (wash-out period) in between two study days.
      Participants will consume bread with either beta-glucan or no additive at a quantity of 25 g
      available carbohydrates within 10 minutes together with 250 ml water. Gastric emptying will
      then be measured by ultrasound during the next 2 hours in 15 minute-intervals the first hour,
      and then every 30th minute (15, 30, 45, 60, 90, and 120 minutes). Blood samples will be taken
      for measurement of postprandial glucose and satiety hormones, and the participants will fill
      in a Visual Analogue Scale (VAS) for satiety. Blood pressure, body weight, waist
      circumference, and height will be measured during the study visit. The participants must be
      fasting for at least 12 hours (overnight, usually from 8 pm the evening before the study
      visit).

      Study bread will be blinded to both the investigators and the participants, although it
      cannot be excluded that participants may recognize the type of bread. Consumption of bread
      occurs in a randomized order, according to a randomization scheme.

      Gastric emptying by ultrasound

      Measurement: The participant is to be placed in a standardized sitting position. The
      cross-sectional area of the antrum of the stomach will be measured using 2D ultrasonography.
      The outer profile of the antrum will be measured using a built-in caliper and a calculation
      program available in the ultrasound apparatus. The gastric antrum, the mesenteric vein, and
      the aorta have to be visualized in this section. A minimal amount of force must be applied
      during each reading to prevent compression of the antrum. The measurement will be performed
      when the participants are suspending their breathing in expiration, between antral
      contractions. The average of the two measurements will be used.

      The antral area will be measured at the fasting state (baseline), immediately following bread
      and water intake, and during the next 2 hours at regular intervals.

      Blood glucose and satiety hormones

      The effect of gastric emptying on postprandial blood glucose will be measured by collecting
      venous and capillary blood samples. Venous blood samples, sampled via a catheter inserted
      into an arm vein, will be collected at baseline, and 15, 30, 45, 60, 90, and 120 minutes
      after the participant starts to ingest the test meal. In addition, the venous blood samples
      will be used for the determination of insulin, Glucagon-like peptide-1 (GLP-1), peptide YY
      (PYY), ghrelin, and leptin. The capillary blood samples, collected at the same time intervals
      as the venous blood samples, will be used to measure postprandial blood glucose levels.

      Satiety

      The participants will be asked to report satiety sensations by filling in a VAS at baseline,
      and 15, 30, 45, 60, 90, and 120 minutes after consumption of the standardized meals, without
      having the previous scale available.

      Statistics

      The primary outcome variable is the difference in gastric emptying (antral area, cm2) at
      different time points and the calculated area under the curve for the entire study duration.
      The comparison of the antral area following the different bread-options will be done at each
      time point using a Tukey's multiple comparisons test. Each subject serves as her/his control
      when comparing antral areas at different time points.

      Secondary outcomes are the postprandial blood glucose concentrations at different time
      points, subjectively reported satiety, insulin, and satiety hormones at different time
      points.

      Ethics

      Participants will be provided with written and oral information about the study. Before
      inclusion, the participants have to sign a consent form. The participants can withdraw from
      the study at any time without explanation. The study will be performed following the
      Declaration of Helsinki.

      Overall, participation in the study implies very little risk. Some discomfort may occur when
      drawing blood and bruising can occur. However, blood sample collection will be performed by
      authorized personnel in a standardized matter. Participants will be covered by the Patient
      Injury Act.

      All study procedures will be conducted in accordance with Good Clinical Practice. All study
      procedures will be described in standard operating procedures (SOPs).
    

Intervention name(s): Beta-glucan bread
Intervention type(s): Other
Intervention description(s): Beta-glucan is a dietary fiber with beneficial health effects, both on cholesterol levels and potentially blood glucose levels.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Prevention
Keywords: Gastric emptying; Carbohydrate; Bread consumption; Beta-glucan; Metabolic response