Neomycin has no persistent sparing effect on vitamin B-12 status in pectin-fed rats |
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Authors: | R W Cullen S M Oace |
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Affiliation: | Department of Nutritional Sciences, University of California, Berkeley 94720. |
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Abstract: | In the present study, rats were depleted of vitamin B-12 with fiber-free or 5% pectin diets, with or without neomycin. Through use of this intestinal antibiotic reported to "spare" vitamin B-12, we sought to determine if bacterial fermentation of pectin might explain our previous observations of negative effects of pectin on vitamin B-12 status. However, neomycin did not lessen interference by pectin with vitamin B-12 metabolism. Pectin increased urinary methylmalonate and decreased propionate oxidation to a greater extent in the presence than in the absence of neomycin. Also, regardless of the presence of neomycin, the biologic half-life of injected [57Co]vitamin B-12 was 58 d for rats fed the fiber-free diets and only 38 d for rats fed 5% pectin diets. Neomycin delayed early fecal excretion of 57Co but had no persistent effect. Thus, neomycin-sensitive bacteria do not mediate the negative effects of pectin on vitamin B-12 status. Pectin may interfere directly with vitamin B-12 absorption or may stimulate vitamin B-12 uptake or propionate production by microbial species that have adapted to neomycin. |
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