Analyses of human fecal and ileostomy samples by a method that is sensitive and free from interferences indicate that nitrate and nitrite levels in the intestine are lower than reported previously. Fecal nitrate and nitrite concentrations ranged from 0 to 14 µmol/kg (0 to 0.9 ppm) and 5 to 19 µmol/kg (0.3 to 0.9 ppm), respectively. Ileostomy samples contained from 0 to 7 µmol/kg (0 to 0.4 ppm) and 0 to 15 µmol/kg (0 to 0.7 ppm) for nitrate and nitrite, respectively. We also showed that, when deliberately added to feces samples, nitrate and nitrite were destroyed during a two-hr incubation period in a reaction that depended on the presence of microorganisms. The results suggest that conditions in the lower gastrointestinal tract favor denitrification, not nitrification as had been proposed previously.

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Supported by the Ontario Cancer Treatment and Research Foundation, the National Cancer Institute of Canada, and the Medical Research Council of Canada. The research described herein was presented in part at the Conference on Carcinogen and Mutagen Formation in the Gastrointestinal Tract at the Banbury Center, Cold Spring Harbor Laboratory, Cold Spring Harbor, N. Y., October 12 to 15, 1980.

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©1981 American Association for Cancer Research.
1981
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