• cereal dietary fiber;
  • glucose response;
  • gut health;
  • human intervention studies;
  • insulin response;
  • molecular structure

Epidemiological and animal data show associations between whole grain and dietary fiber intakes and disease risk reduction. Dietary fiber can be considered a “black box” since its molecular structure can vary significantly. Limited data are available linking the health effects of dietary fiber to certain molecular structures. The present review was conducted to examine the existing knowledge of structure/effect relationships with a focus on human intervention studies that examined the relationships between the molecular structure of cereal dietary fiber and both the blood glucose and insulin responses and gut health. An extensive search of the existing literature was conducted using the PubMed database for the period 1993–2008. Of 48 publications originally identified using the search criteria, 13 provided molecular information in conjunction with fiber type. Several indications show a link between molecular structure and physiological effects. Limited data from human intervention trials are available to verify hypotheses derived from in vitro studies that relate the molecular structure of cereal dietary fiber to both insulin and glucose response and gut health.