The Impact of Broad Bean Hull on Blood Glucose Control and Gut Health
Condition: Healthy; Overweight
MeSH terms: Overweight
Study type: Interventional

Summary: 
      This study aims to assess the effects of broad bean hull (BBH) consumption on blood glucose
      and gut health. Broad bean (Vicia faba) is widely cultivated in Scotland, with the UK being
      the most significant European producer. The seed coat (hull or testa) is removed during broad
      bean processing. This is a significant secondary product that is largely discarded.
      Preliminary work showed that this material is comparable to wheat bran and is rich in fibre
      (49%) and protein (18%). Additionally, it showed a rich phytochemical profile and lower fat
      and carbohydrate content than wheat bran. Experiments also showed that BBH inhibited the
      activity of alpha-amylase and alpha-glucosidase enzymes, suggesting anti-diabetic properties.
      Overall, these results showed that BBH is a secondary crop product having potential as a
      functional food for humans. Therefore, the objective of this study is to assess in vivo in
      humans the physiological and functional effects of BBH. Using an acute phase randomised
      controlled crossover design, the study will assess how consuming BBH fortified breads affects
      plasma glucose and gut health. The study will recruit 18 volunteers, normal-overweight, aged
      18-75 years, who habitually consume low amounts of fruits and vegetables (≤3 portions/day).
      The volunteers will attend two identical stand-alone intervention sessions lasting three days
      each following the screening. The order of the intervention sessions will be randomised. On
      the day before each intervention session, the participants will provide a baseline faecal
      sample and have a continuous glucose monitoring sensor (CGMS) attached. They will be also be
      given a standardised dinner. On the next morning, following a 10-12 hr fast, an indwelling
      antecubital cannula will be inserted, and a blood sample will be taken for measuring baseline
      levels of metabolites. The volunteers will be given a standardised portion of the BBH or
      control bread to consume, and further blood samples taken for the subsequent four hours.
      Breath samples will also be taken at the same time points for measuring gastric emptying. The
      volunteers will be provided with all the meals for the rest of the day and the subsequent two
      days. These will include two portions per day of either the BBH or control bread. The meals
      will be standardised for energy and macronutrients. The volunteers will be instructed to
      return to the Human Nutrition Unit on the fourth morning and provide a second faecal sample
      and remove the CGMS. Blood samples will be analysed for systemic bioavailability and
      metabolism of test meal components, glucose regulatory hormones and breath samples for
      quantifying gastric emptying. The faecal samples will be analysed for gut bioavailability and
      metabolism of test meal components, microbial counts, composition, and water content.
    

Detailed description: 
      The study aims to confirm in vivo the effects of consuming broad bean hull on blood glucose
      control and gut health. Although in vitro evidence is promising, its benefits remain
      confirmed in vivo in humans. No studies have previously attempted to assess the impact of
      broad bean hull consumption on glycaemic and gut health outcomes in humans. Therefore, this
      study will be novel and provide useful information on the potential of using BBH as a
      functional food for human health.

      From a health perspective, it is essential to establish the bioavailability and metabolism of
      dietary constituents in humans. Certain metabolites are absorbed early in the
      gastrointestinal tract, whereas others are transported to the colon, where they are
      extensively metabolised by the gut microbiota. This study will characterise the bioactive
      metabolites present in the plasma and faecal samples obtained. This will inform on their
      availability to the systemic circulation and their excretion profiles.

      Using targeted quantitative analysis (LC-MS and GC-MS), metabolites and their in vivo
      concentrations will be measured. The principal metabolites analysed will be those produced by
      the phenylpropanoid pathway and protein and carbohydrate metabolism products. These will
      include derivatives and metabolites of the simple phenols, benzoic acids, phenolic acids,
      phenylacetic acids, phenypropionic acids, phenylpyruvic acids, phenyllactic acids, mandellic
      acids, phenolic dimers, acetophenones, benzaldehydes, cinnamaldehydes, benzyl alcohols,
      cinnamyl alcohols, indoles, isoflavones, coumarins, chalcones, flavanones, flavones,
      flavonols, anthocyanidins.

      Furthermore, short-chain fatty acids will be analysed in the participants' faecal samples. It
      has been shown that many of these compounds are bioactive and exhibit anti-oxidant and
      anti-inflammatory activity at in vivo concentrations. Therefore, these studies will provide
      important information on bioavailability and metabolism and correlate the indices with health
      biomarkers.

      In addition, compounds such as the carcinogenic heterocyclic amines, genotoxic nitrosamines,
      indoles, polyamines, bile acids, and other protein metabolites considered detrimental to
      human health will also be measured. It is likely, the carbohydrate and phytochemical content
      of plant proteins may also protect against the formation of these toxic and potentially
      carcinogenic protein by-products.
    

Intervention name(s): Experimental: Bean Hull Bread; Experimental: Plain Bread
Intervention type(s): Other; Other
Intervention description(s): The bean hull bread will deliver 21.96 g of fibre. Volunteers will consume a roll of bean hull bread (155g/portion) served with 25g of raspberry jam.; The control bread will deliver 4.53 g of fibre. Volunteers will consume a roll of plain bread (122g/portion) served with 25g of raspberry jam.
Other intervention name(s): Broad Bean Hull Bread; Control Bread
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: Randomised controlled crossover non-blinded design
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: gut bioavailability; plasma metabolites; faecal metabolites; broad bean hull; high fibre; Vicia faba