Effect of Vegetables, Tea, and Soy on Endogenous N-Nitrosation, Fecal Ammonia, and Fecal Water Genotoxicity During a High Red Meat Diet in Humans

• Published in: Nutrition and cancer Vol. 42; no. 1; pp. 70 - 77
• Main Authors: Hughes, Roisin, Pollock, Jim R.A, Bingham, Sheila
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA Franklin Institute Press 2002; Lawrence Erlbaum Associates, Inc; Taylor& Francis
• Subjects: Adult; ammonia; Ammonia - metabolism; Biological and medical sciences; broccoli; Brussels sprouts; Colon - physiology; colorectal neoplasms; Diet; DNA Damage; excretion; Feces - chemistry; Gastroenterology. Liver. Pancreas. Abdomen; genotoxicity; Glycine max; Humans; Meat; meat consumption; Medical sciences; Middle Aged; mucosa; Nitrosation; red meat; risk; Stomach. Duodenum. Small intestine. Colon. Rectum. Anus; Tea; Tumors; Vegetables; volunteers; Water; United Kingdom; Europe; Water; Human; Rectal disease; Vegetables; Toxicity; Soy product; Genotoxicity; Malignant tumor; Nitrosation; Epidemiology; Meat; Colonic disease; Prevention; Ammonia; Tea; Diet; Risk factor; Rectum; Digestive diseases; Intestinal disease; Colon; Feces; Public health
• ISSN: 0163-5581; 1532-7914
• DOI: 10.1207/S15327914NC421_10

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 μg NO2/g).