Abstract
BackgroundIn some studies, high intake of dietary fibre has been associated with a lower risk of colorectal cancer. The present study aimed to compare physiological effects of three legume kernel fibres and citrus fibre on blood lipids (primary outcome: LDL cholesterol) and colonic health.MethodsNinety-two subjects were recruited for the double-blind, controlled crossover trial. Seventy-eight participants were randomly divided into three groups. Following run-in, half the volunteers from each group consumed 25 g/d of a legume fibre, comprising blue lupin fibre, white lupin fibre, and soya fibre for two weeks. The other half received the same amount of citrus fibre (active comparator). The intervention was crossed within each group after two weeks wash-out. At the end of run-in and intervention, a quantitative faeces collection took place and fasting blood samples were drawn. Repeated measures ANOVA with the general linear model were applied to evaluate changes following interventions.ResultsSeventy-six subjects completed the study. Dietary fibre intake during all interventions was approximately twice the fibre intake at run-in. The lupin fibre supplementations increased daily faecal dry matter and faecal weight compared to run-in, representing an increase of 1.76 g faeces/g additional dietary fibre contributed by blue lupin and of 1.64 g faeces/g by white lupin, respectively. Both lupin interventions led to a significantly enhanced formation of short-chain fatty acids, and blue lupin fibre to a decrease in faecal pH compared to run-in (0.27 units, P < 0.01). Further, blue lupin increased primary bile acids-excretion (P = 0.02). All legume fibres reduced faecal concentrations of total and secondary bile acids (blue lupin: 16%; white lupin: 24%; soya: 16%). Blood lipids were not influenced by any intervention. No serious adverse effects were observed.ConclusionsThe tested fibre preparations do not affect lipid metabolism through bile acid-binding in normocholesterolaemic subjects. However, particularly blue lupin kernel fibre improve colonic function and have beneficial effects on putative risk factors for colorectal cancer such as faecal mass, transit time, SCFA, faecal pH, and secondary bile acid concentration. Therefore, enhancing dietary fibre intake through blue lupin up to about 50 g/d can be recommended.Trial registrationNCT01036308
Highlights
In some studies, high intake of dietary fibre has been associated with a lower risk of colorectal cancer
The World Cancer Research Fund (WCRF), in conjunction with the American Institute for Cancer Research (AICR), released an updated meta-analysis of 25 prospective studies in 2011, which concludes that 10 g/d of total dietary fibre decreases the relative risk of colorectal cancer by 10% [2,17]
Faecal composition and bowel habits The lupin fibre supplementations increased the daily faecal dry matter and faecal weight compared to run-in, representing an increase of 1.76 g faeces/g additional dietary fibre contributed by blue lupin intervention and of 1.64 g faeces/g white lupin, respectively (Table 3)
Summary
High intake of dietary fibre has been associated with a lower risk of colorectal cancer. A high intake of dietary fibre has been associated in some, but not all, studies with a lower risk of colorectal cancer. Many epidemiological studies support Burkitt’s hypothesis that increased dietary fibre intake leads to a reduced risk of colorectal cancer [4,5,6], while others revealed contradictory effects [7,8]. The World Cancer Research Fund (WCRF), in conjunction with the American Institute for Cancer Research (AICR), released an updated meta-analysis of 25 prospective studies in 2011, which concludes that 10 g/d of total dietary fibre decreases the relative risk of colorectal cancer by 10% [2,17]
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