Digestibility of Selected Resistant Starches in Humans
Condition: Malabsorption; Carbohydrate; Ileostomy - Stoma
MeSH terms: Malabsorption Syndromes
Study type: Interventional

Summary: 
      Dietary fiber is a type of carbohydrate which is not digested in the human small intestine.
      Whole grains are a source of dietary fiber that are used to promote health; however, using
      whole grains in commercial products results in a different taste and/or texture than the
      usual products made from refined grains. Thus, other types of high-fiber ingredients have
      been developed which can be incorporated into food products with less effect on their taste
      and/or texture. An example of this is resistant starch, defined as starch which is not
      digested in the human small intestine. The digestibility of starch is usually determined
      in-vitro; however, there is evidence that such methods may overestimate the amount of
      resistant starch by as much as 100%. The measurement of the amount of carbohydrate in the
      ileal effluent, digestive waste, of subjects with an ileostomy is considered to be the best
      in-vivo method of starch digestibility. The subjects collect ileal effluent during the day
      during which time they consume a polysaccharide-free diet. There is evidence that resistant
      starch consumed at breakfast is completely recovered in ileal effluent 8-10hr after
      consumption. The purpose of this study will be to compare the carbohydrate content recovered
      in ileal effluent of 10 subjects with a conventional ileostomy.
    

Detailed description: 
      Dietary fiber consists mainly of carbohydrates which are not digested in the human small
      intestine. A high intake of dietary fiber is associated with many health benefits including,
      but not limited to, improved bowel function and reduced risk of weight gain, cardiovascular
      disease and diabetes. Therefore, there is great interest in the food industry to produce
      products enriched with dietary fiber to promote health. One way to achieve this is to use
      more whole grains (wheat, rice, oats, barley) as ingredients in products such as breakfast
      cereals, breads and food bars. However, the use of whole grains results in products which
      have a different taste and/or texture than the usual products made from refined grains. Thus,
      other types of high-fiber ingredients have been developed which can be incorporated into food
      products with less effect on their taste and/or texture. Examples of such ingredients are
      inulin (an oligosaccharide containing fructose) and resistant starch. Resistant starch,
      defined as starch which is not digested in the human small intestine, is present in small
      amounts (2-5% of total starch) in many normal foods.

      Starch is the most abundant energy containing nutrient in the human diet; it consists of 2
      types of polysaccharides: amylose, is a linear polymer consisting of long chains of glucose
      molecules joined by 1-4 linkages; and amylopectin, a highly branched polymer consisting of
      long chains of glucose molecules joined by 1-4 linkages with numerous 1-6 linkage branch
      points. Most (70-80%) of the starch in normal starchy foods (eg. cereals and potatoes) is
      amylopectin. Amylopectin is highly digestible because its branched structure makes it readily
      able to gelatinize, the process whereby adjacent starch molecules swell and separate from
      each other under the influence of moist heat (ie. cooking). By contrast amylose is less
      digestible because its linear structure allows adjacent molecules to associate by hydrogen
      bonding which reduces their ability to gelatinize. Some types of commercially available
      resistant starch come from strains of corn which produce starch containing 70 to 100%
      amylose.

      The digestibility of starch is usually determined in-vitro using methods involving digestion
      of the starch with α-amylase under pH and temperature conditions thought to mimick digestion
      in the human small intestine. However, there is evidence that such methods may overestimate
      the amount of resistant starch by as much as 100%. Methods used to estimate starch
      digestibility in-vivo include the breath hydrogen method and the measurement of the amount of
      carbohydrate in the ileal effluent of subjects with an ileostomy. The latter is considered to
      be the best in-vivo method which involves preparation of subjects with a polysaccharide-free
      diet the day before then consumption of the test carbohydrate with breakfast. Subjects
      collect ileal effluent during the day during which time they consume a polysaccharide-free
      diet. There is evidence that resistant starch consumed at breakfast is completely recovered
      in ileal effluent 8-10hr after consumption. The objective of this study is to determine the
      amount of carbohydrates in 3 commercially available starches (Hi-Maize® 260, Hylon® VII and
      Amioca corn starch) which escape digestion in the human small intestine.
    

Intervention name(s): Starch-free breakfast; Hi-Maize 260; Hylon VII; Amioca
Intervention type(s): Other; Other; Other; Other
Intervention description(s): Starch-free breakfast alone; Starch-free breakfast plus 55.3g Hi-Maize 260; Starch-free breakfast plus 56.9g Hylon VII; Starch-free breakfast plus 56.4g amioca starch
Intervention model: Single Group Assignment
Masking: None (Open Label)
Keywords: Resistant starch; Ileostomy; In vivo; Carbohydrate digestibility