British Journal of Nutrition

Nutritional Effects of Biologically Active Components of Plants

Rape-seed meal toxicity in gnotobiotic rats: influence of a whole human faecal flora or single human strains of Escherichia coli and Bacteroides vulgatus

Sylvie Rabota1, Lionelle Nugon-Baudona1, Pierre Raibauda1 and Odette Szylita1

a1 Unité d'Ecologie et de Physiologie du Systeme Digestif Centre de Recherches de Jouy, Institut National de la Recherche Agronomique, 78352 Jouy-en-Josas Cédex, France


Gnotobiotic growing rats harbouring either a whole human faecal flora or single human strains of Escherichia coli (EM0) or Bacteroides vulgatus (BV8H1) were fed for 7 weeks on semi-synthetic diets in which the protein source was either soya-bean meal (SM) or rape-seed meal (RM). For each bacterial status the RM-diet group was compared with the control group fed on the SM diet. The association of human faecal flora with the RM diet was responsible for reduced feed intake and reduced weight gain, an enlargement of the liver and thyroid and a decrease in both thyroxine and triiodothyronine plasma levels. The association of the B. vulgatus BV8H1 strain with the RM diet reproduced all these effects, except that triiodothyronine plasma levels were not significantly modified. Rats inoculated with the E. coli EM0 strain and fed on the RM diet exhibited a goitre and lowered thyroxine and triiodothyronine plasma levels. These results show that the human intestinal microflora may be involved in glucosinolate metabolism when cruciferous vegetables are consumed by man. The specificity of the symptoms observed according to the rat bacterial status supports the hypothesis that bacteria yield specific toxic glucosinolate derivatives according to their enzymic potential.

(Received January 06 1992)

(Accepted September 07 1992)