The effect of dietary fibre on reducing the glycaemic index of bread

Abstract

As bread is the most relevant source of available carbohydrates in the diet and as lowering dietary glycaemic index (GI) is considered favourable to health, many studies have been carried out in order to decrease the GI of bread. The most relevant strategy that has been applied so far is the addition of fibre-rich flours or pure dietary fibre. However, the effectiveness of dietary fibre in bread in reducing the GI is controversial. The purpose of the present review was to discuss critically the effects obtained by adding different kinds of fibre to bread in order to modulate its glycaemic response. The studies were selected because they analysed in vivo whether or not dietary fibre, naturally present or added during bread making, could improve the glucose response. The reviewed literature suggests that the presence of intact structures not accessible to human amylases, as well as a reduced pH that may delay gastric emptying or create a barrier to starch digestion, seems to be more effective than dietary fibre per se in improving glucose metabolism, irrespective of the type of cereal. Moreover, the incorporation of technologically extracted cereal fibre fractions, the addition of fractions from legumes or of specifically developed viscous or non-viscous fibres also constitute effective strategies. However, when fibres or wholemeal is included in bread making to affect the glycaemic response, the manufacturing protocol needs to reconsider several technological parameters in order to obtain high-quality and consumer-acceptable breads. Key words: Dietary fibre: Glycaemic index: BreadAt the global level, cereals and starch-based staples outweigh all other foodstuffs as sources of daily dietary energy. Among these foods, white bread prepared with wheat flour is the most frequently consumed cereal product (1) , and, in turn, it is the main contributor to the glycaemic index (GI) of the human diet (2) . It is well known that white bread starch is rapidly digested and absorbed, eliciting high glucose and insulin responses (3) , and this characteristic makes bread a high-GI food (.70) (4) . As bread is the most relevant source of available carbohydrates (CHO) in the diet and as lowering dietary GI is considered favourable to health, many studies have been carried out in order to decrease the GI of bread. The most relevant strategy that has been applied so far is the addition of fibre-rich flours or pure dietary fibre, which also adds nutritional value to bread. In fact, besides putatively influencing the glycaemic response, this approach enables the amount of dietary fibre offered to the population to be increased. However, the effectiveness of dietary fibre in bread in reducing the GI is controversial. Thus, the key issues of the present review are whether dietary fibre is able to reduce bread GI, which are the main mechanisms involved and which other approaches can be alternatively used for this purpose. Glycaemic index conceptThe GI is a parameter used to rank CHO food items based on their glycaemic potential (...

Effect of macronutrients and fiber on postprandial glycemic responses and meal glycemic index and glycemic load value determinations

“…Because bread is the most frequently consumed source of available carbohydrate, many strategies have been used to reduce the postprandial glucose and insulin responses to bread. One of the main strategies has been to replace breads that are made from refined gains with whole grains or by increasing fiber intake from other sources (61). Notwithstanding the benefits of fiber with respect to gastrointestinal function, the data to support benefits for the glycemic response have been inconsistent.…”

“…Some studies have reported that fiber-rich foods, either soluble or insoluble fiber, resulted in lower glucose AUC i (28,29,(62)(63)(64)(65)(66)(67), insulin AUC i (62,64,67,68), and GI or GL (28,29,65,66,68,69) values. This effect has been attributed to the ability of fiber to increase the gastrointestinal content viscosity, to decrease the gastric-emptying rate, and to slow glucose-absorption rates (61,62). In contrast, other studies have reported that the fiber content in foods, regardless of the type, has no significant effect on the postprandial glucose response (22,62,(70)(71)(72)(73), insulin response (62,70,71), or GI or GL values (73).…”

“…Cheerios cereal is made from oats, which contain primarily soluble fiber in the form of b-glucan. The ability of b-glucan to attenuate postprandial glycemic and insulin responses has been attributed to its viscous nature (61,62,66). However, the effect of food processing on b-glucan during the manufacturing of Cheerios cereal is unknown; hence, the possibility that the b-glucan is degraded cannot be ruled out.…”

“…However, the effect of food processing on b-glucan during the manufacturing of Cheerios cereal is unknown; hence, the possibility that the b-glucan is degraded cannot be ruled out. Note that, during food preparation, fibercontaining foods can differ in many ways because of physical disruption and heat exposure (61). Thus, it is difficult to attribute the results solely to the presence or absence of dietary fiber.…”

Nutrients, Nutraceuticals and Xenobiotics Affecting Renal Health

“…An adequate dietary fiber intake in diet can indeed modulate human metabolism thanks to its action on glycaemic index reduction [26], satiety induction, cholesterol absorption, and BP reduction [4]. Dietary fiber content in diet is also effective in supporting weight loss and glycaemic control, probably not only by the mechanisms of satiation, delayed gastric emptying and decreased absorption of nutrients [27,28], but also by modulating the gut endocrine and metabolic orchestra [5,27].…”