Effect of vegetables, tea, and soy on endogenous N-nitrosation, fecal ammonia, and fecal water genotoxicity during a high red meat diet in humans.

TitleEffect of vegetables, tea, and soy on endogenous N-nitrosation, fecal ammonia, and fecal water genotoxicity during a high red meat diet in humans.
Publication TypeJournal Article
Year of Publication2002
AuthorsHughes, R, Pollock, JRA, Bingham, S
JournalNutr Cancer
Volume42
Issue1
Pagination70-7
Date Published2002
ISSN0163-5581
KeywordsAdult, Ammonia, Colon, Diet, DNA Damage, Feces, Humans, Meat, Middle Aged, Nitrosation, Soybeans, Tea, Vegetables, Water
Abstract

Red meat increases colonic N-nitrosation, and this may explain the positive epidemiological relationship between red meat intake and colorectal cancer risk. Vegetables, tea, and soy have been shown to block N-nitroso compound (NOC) formation and are associated with protection against colorectal cancer. To determine whether these supplements affect fecal NOC excretion during consumption of a high red meat (420 g/day) diet, 11 male volunteers were studied over a randomized series of 15-day dietary periods. Seven of these subjects completed a further dietary period to test the effects of soy (100 g/day). Soy significantly suppressed fecal apparent total NOC (ATNC) concentration (P = 0.02), but supplements of vegetables (400 g/day as 134 g broccoli, 134 g brussels sprouts, and 134 g petits pois) and tea extract (3 g/day) did not affect mean levels of fecal ATNC, nitrogen and ammonia excretion, and fecal water genotoxicity. However, fecal weight was increased (P < 0.001) and associated with reduced transit time (r = 0.594, P < 0.0001), so that contact between ATNC, nitrite, and ammonia and the large bowel mucosa would have been reduced. Longer transit times were associated with elevated fecal ATNC concentrations (r = 0.42, P = 0.002). Fecal nitrite was significantly suppressed during the tea supplement compared with the meat-only (P = 0.0028) and meat + vegetables diets (P = 0.005 for microgram NO2/g).

DOI10.1207/S15327914NC421_10
Alternate JournalNutr Cancer
Citation Key10.1207/S15327914NC421_10
PubMed ID12235653