Comparative digestibility of wholemeal and white breads and the effect of the degree of fineness of grinding on the former

Abstract

The first satisfactory experiments on the relative digestibility of wholemeal and white breads were carried out by Rubner (1883), whose results are current in physiological text-books throughout the world. His inquiry was undertaken at the instigation of the British Bread Reform League, who supplied the wholemeal flour. The white flours were ordinary straight run (70 % extraction). A further series of experiments was begun at

Gastrointestinal responses of rats fed on white and wholemeal breads: complex carbohydrate digestibility and the influence of dietary fat content

“…Direct comparison of the results from the present study with those in the literature on the digestibility of complex carbohydrates in breads are complicated, not only by problems of experimental protocol but also by differences in the methods used to determine the non-starch fraction of the polysaccharides. Early studies by, for example, Macrae et al (1942) Wine, 1967). The most comparable study is that by Ranhotra et al (1988) who, using the 'dietary fibre' method of Prosky et al (1984), obtained digestibilities of 82 and 44 YO for white and wholemeal breads respectively in the rat.…”

“…This assumes, implicitly or explicitly, that the addition of the test food has no effect on the digestibility of the basal diet (or vice versa), i.e. that there are no associative effects; an assumption, with uncertain validity, which has long been recognized (see Macrae et al 1942). An alternative approach, used for example by Macrae et al (1942) and McCance & Walsham (1948), is to arrange that the test foodstuff makes up as much as possible of the experimental diets and that the other components (necessary for palatability or to ensure nutritional adequacy) contain a minimum of the nutrients under investigation.…”

“…that there are no associative effects; an assumption, with uncertain validity, which has long been recognized (see Macrae et al 1942). An alternative approach, used for example by Macrae et al (1942) and McCance & Walsham (1948), is to arrange that the test foodstuff makes up as much as possible of the experimental diets and that the other components (necessary for palatability or to ensure nutritional adequacy) contain a minimum of the nutrients under investigation. For example, in the studies of Macrae et al (1942) bread contributed 74 and 90% of the energy and N intakes respectively and virtually all the complex carbohydrates, whilst in the studies of McCance & Widdowson (1942a) bread provided 40-50 YO of energy and most of the calcium, the main mineral under investigation.…”

“…An alternative approach, used for example by Macrae et al (1942) and McCance & Walsham (1948), is to arrange that the test foodstuff makes up as much as possible of the experimental diets and that the other components (necessary for palatability or to ensure nutritional adequacy) contain a minimum of the nutrients under investigation. For example, in the studies of Macrae et al (1942) bread contributed 74 and 90% of the energy and N intakes respectively and virtually all the complex carbohydrates, whilst in the studies of McCance & Widdowson (1942a) bread provided 40-50 YO of energy and most of the calcium, the main mineral under investigation. In calculating apparent digestibilities, Macrae et al (1942) (1948) referred to digestibilities of particular diets rather than to the individual breads which were their largest components.…”

“…For example, in the studies of Macrae et al (1942) bread contributed 74 and 90% of the energy and N intakes respectively and virtually all the complex carbohydrates, whilst in the studies of McCance & Widdowson (1942a) bread provided 40-50 YO of energy and most of the calcium, the main mineral under investigation. In calculating apparent digestibilities, Macrae et al (1942) (1948) referred to digestibilities of particular diets rather than to the individual breads which were their largest components. In our experimental diets, bread, either white or wholemeal, provided all the complex carbohydrates and approximately 90 Yo of DM intake.…”