Bread Replacement - Facing the Challenge to Improve Its Quality for Better Metabolic Health
Condition: Bread; Hyperglycemia; Glycemic Control; PreDiabetes
MeSH terms: Hyperglycemia
Study type: Interventional

Summary: 
      This is a multicenter study testing the effect of bread containing beta-glucan on glycemic
      control in participants with intermediate hyperglycemia. The main hypothesis of the study is
      that bread enriched with beta-glucan will have a positive effect on blood glucose control
      (HbA1c) in persons with intermediate hyperglycemia.

      Bread (intervention and control) will be produced by Nofima (Ås, Norway) using food-grade
      beta-glucan from oat and barley and shipped to the study centers (Bergen (N), Gothenburg (S),
      Paderborn, and Leipzig (D)) and there distributed for free to the participants of the study.
      The study will last for 16 weeks with measurements at baseline, after 8 weeks and after 16
      weeks. Blood and urine samples will be taken, anthropometry and body composition measured,
      and questionnaires on health status and socio-economic status, physical activity, nicotine
      use, alcohol habits, chronotype, quality of life, and consumer acceptance of the study bread
      will be filled in.
    

Detailed description: 
      Carbohydrates are the main source of energy in most European countries with intakes ranging
      from 40-60% of total energy. Consequently, the role of its quality and quantity for the
      development of metabolic diseases is the focus of substantial debate. Notwithstanding,
      replacing processed carbohydrates with unprocessed carbohydrates is regarded as a major
      strategy to improve public health. This is to a substantial degree based on strong
      observational evidence that higher intakes of dietary fiber (cereal grains containing the
      same relative proportions of bran, germ, and endosperm as the intact caryopsis) are
      associated with lower risks of total mortality, cardiovascular morbidity, and mortality, type
      2 diabetes mellitus (T2DM) incidence and cancer mortality. Nonetheless, data from medium- to
      long-term intervention studies among adults are less conclusive regarding the benefits of
      whole-grain consumption on glycemic control, bodyweight and serum lipids. In fact, benefits
      may be largely confined to whole grains stemming from oats or barley, calling for explicit
      consideration of these whole grains and/or its mechanistically relevant component.

      Adding complexity, many commonly consumed whole grains or products rich in dietary fiber are
      characterized by a high glycemic index (GI>70), in fact, a high dietary fiber content will
      not predict a low glycemic response. The GI describes the glycemic potency of the available
      carbohydrates in a food, is measured under defined conditions and is used to calculate the
      glycemic load (GL: GI x amount of available carbohydrates). Preferred consumption of high GI
      grain products is of concern since a higher dietary GI and GL may be causally linked to a
      substantial increase in T2DM risk and may translate into a considerable health burden.

      In European societies, T2DM prevalence is increasing as a result of higher overweight and
      obesity rates and increases in longevity. Efforts are hence needed to develop
      carbohydrate-based food items that are both rich in fiber and whole grain and have a low GI
      and tailored to the dietary habits of middle-aged adults with insulin resistance (also called
      'pre-diabetes' or intermediate hyperglycemia defined by intermediately increased HbA1c
      levels). This stage precedes clinical T2DM and affects up to 30% of adults in Western
      societies.

      Enrichment with selected fibers, e.g. beta-glucan from oat and barley, may offer an
      alternative to whole grain kernel breads, which may not meet consumer preferences and is also
      endorsed by EFSA health claims. Preliminary small-scale studies indicate acute, short- and
      longer-term benefits of such bread for glycemic and/or insulinemic responses among persons
      with T2DM or at risk of T2DM. However, these studies suffer, besides the small sample sizes,
      from high amounts of test food (8 servings per day = 320 g bread) and use of white bread as a
      comparator. The present study will test whether habitual consumption of a bread containing
      oat bran concentrate and meeting the high beta-glucan content of the EFSA claim (4.3 g
      beta-glucan per 30 g available carbohydrate) compared to normal wheat bread high in whole
      grain but without kernels will affect glycemic control over a period of 16 weeks.

      Main hypothesis The main hypothesis of the study is that bread enriched with beta-glucan will
      have a positive effect on blood glucose control (HbA1c) in persons with intermediate
      hyperglycemia.

      Objectives Main objective: Establish whether replacement of habitual bread intake with a low
      GI bread containing beta-glucan improves glycemic control among persons at risk for T2DM.

      Secondary objectives: Examine the effects of the intervention on capillary blood glucose,
      body composition and serum lipid levels, and address consumer acceptance of the intervention
      bread.

      Study procedures This is a multicenter study testing the effect of bread containing
      beta-glucan on glycemic control in participants with intermediate hyperglycemia.

      Breads (intervention and control) will be produced by Nofima (Ås) using food-grade
      beta-glucan from oat and barley and shipped to the study centers (Bergen (N), Gothenburg (S),
      Paderborn and Leipzig (D)) and there distributed for free to the participants of the study.
      The study will last for 16 weeks with measurements at baseline, after 8 weeks and after 16
      weeks. Blood and urine samples will be taken, anthropometry and body composition measured,
      and questionnaires on health status, chronotype, lifestyle, and acceptance of the breads will
      be filled in.

      Recruitment of participants Each study site is responsible for the recruitment of the planned
      numbers of participants. Potential participants will be recruited through flyers and
      information to local General Practitioners, advertising in local newspapers, central and
      local social media announcements (websites of universities, Facebook). Potentially eligible
      participants will be invited to a screening visit and checked for eligibility and exclusion
      of undiagnosed 2TDM.
    

Intervention name(s): Beta-glucan bread
Intervention type(s): Other
Intervention description(s): Frozen bread is administered to the participants for home storage. Bread is thawed at home before consumption. Dosage: At least 3 slices of bread 6 days per week for 16 weeks
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: Multicenter
Masking: Double (Participant, Investigator)
Primary purpose: Prevention
Keywords: beta-glucan; hyperglycemia; pre-diabetes