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

Abstract

To obtain quantitative information on the digestibility of the non-starch polysaccharides (NSP) fraction of white and wholemeal breads, rats were fed on diets in which freeze-dried bread (white, wholemeal or mixtures of the two) provided all the complex carbohydrates. In a second experiment the possibility that dietary fat concentration might influence NSP digestibility was tested by feeding diets containing 30 or 170 g maize oil/kg and either white or wholemeal bread. Multiple linear regression analysis provided little evidence of associative effects of dietary components on N S P digestibility and in the two experiments digestibilities of NSP for white and wholemeal breads were 0.77482 and 0.47-0.52 respectively. Xylose-and arabinose-containing polymers were better digested than was cellulose for both breads. Replacing white by wholemeal bread markedly increased the molar proportion of butyrate in caecal volatile fatty acids at the expense of acetate. This was associated with greater flows of organic matter to the large bowel (LB) and a reduction in caecal transit time (Expt 2). There was little detectable effect of dietary maize oil concentration on N S P digestibility or on LB fermentation. All breads contained some starch resistant to pancreatic a-amylase (EC 3 . 2 .

Comparative gastrointestinal and plasma cholesterol responses of rats fed on cholesterol-free diets supplemented with guar gum and sodium alginate

“…Approximately 100 % disappearance of guar gum within the alimentary tracts of rats and human subjects has been reported (Nyman et al 1986), but to our knowledge the present study is the first study that has attempted to determine the effect of an oral dose of guar gum (or sodium alginate) on digestibility of the NSP in the hydrocolloid. In contrast to earlier studies in which peas (Pisum sativum); bread and beans (Phaseolus vulgaris) were fed to rats at a range of doses and where there was little evidence of a diminution in digestibility of NSP with higher intakes (Goodlad & Mathers, 1990Key & Mathers, 1993a,b, 1995, the present study provided clear evidence that with 100 g NSP source/kg diet, there was significantly P , 0´001 reduced whole-gut NSP digestibility (Fig. 1).…”

“…The reason for the reduced NSP digestibility with the higher NSP intake was not established, but may be associated with inadequate time for bacterial hydrolysis of the test polymers, since alterations in gut transit time has a strong influence on extent of NSP digestion (Mathers, 1991). There was a strong linear increase in faecal N output with increasing consumption of GG and SA, which is consistent with previous observations in rats fed increasing levels of dietary NSP (for example, see Goodlad & Mathers, 1990;Key & Mathers, 1993a). It has been suggested that increased faecal N output may be due to enhanced loss of endogenous N arising from stimulation of mucosal cell turnover (Skurpakkar et al 1979).…”

The Energy Values of Dietary Fibre and Sugar Alcohols for Man

“…Possible interactions between UCC and dietary fat affecting faecal energy losses are being studied in man (P. Moe, USDA Human Nutrition Laboratory). Key & Mathers (1992) showed that increasing maize oil from 30 to 170 g/kg diet in rats fed either white or wholemeal bread appeared not to influence NSP digestibility, so effects of fat on the energy values of NSP would not be predicted.…”

Wheat bran affects the site of fermentation of resistant starch and luminal indexes related to colon cancer risk: a study in pigs

“…In human diets, RS and NSP coexist, but little is known about the effects of NSP on the fermentation of RS. Key and Mathers21 and Young and colleagues15 found that insoluble NSP increased faecal starch excretion in rats. In addition, the latter group showed that the enhanced tumorigenesis in the distal colon by RS was suppressed by adding wheat bran to the diet.…”