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Only fibres promoting a stable butyrate producing colonic ecosystem decrease the rate of aberrant crypt foci in rats

Abstract

BACKGROUND Dietary fibres have been proposed as protective agents against colon cancer but results of both epidemiological and experimental studies are inconclusive.

AIMS Hypothesising that protection against colon cancer may be restricted to butyrate producing fibres, we investigated the factors needed for long term stable butyrate production and its relation to susceptibility to colon cancer.

METHODS A two part randomised blinded study in rats, mimicking a prospective study in humans, was performed using a low fibre control diet (CD) and three high fibre diets: starch free wheat bran (WB), type III resistant starch (RS), and short chain fructo-oligosaccharides (FOS). Using a randomised block design, 96 inbred rats were fed for two, 16, 30, or 44 days to determine the period of adaptation to the diets, fermentation profiles, and effects on the colon, including mucosal proliferation on day 44. Subsequently, 36 rats fed the same diets for 44 days were injected with azoxymethane and checked for aberrant crypt foci 30 days later.

RESULTS After fermentation had stabilised (44 days), only RS and FOS produced large amounts of butyrate, with a trophic effect in the large intestine. No difference in mucosal proliferation between the diets was noted at this time. In the subsequent experiment one month later, fewer aberrant crypt foci were present in rats fed high butyrate producing diets (RS, p=0.022; FOS, p=0.043).

CONCLUSION A stable butyrate producing colonic ecosystem related to selected fibres appears to be less conducive to colon carcinogenesis.

  • fibre
  • fermentation
  • butyrate
  • colon carcinogenesis
  • aberrant crypt foci
  • rat
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Footnotes

  • Abbreviations used in this paper:
    AC
    aberrant crypt
    ACF
    aberrant crypt foci
    AOM
    azoxymethane
    CD
    low fibre control diet
    FOS
    short chain fructo-oligosaccharide enriched diet
    PCNA
    proliferating cell nuclear antigen
    RS
    type III resistant starch enriched diet
    SCFA
    short chain fatty acid
    WB
    starch free wheat bran enriched diet

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