Dietary carcinogens

A toxic component of braken fern, perhaps either quercetin (105) or ptaquiloside, a glucoside (106), has a mixed history of carcinogenicity. It is sometimes impHcated in an increased incidence of bladder cancer in animals and esophageal cancer in humans. Multiple other dietary components seem to either promote or interfere with its action, and the significance of braken fern in human carcinogenesis remains unproven. 

Vanillin has a low potential for acute and chronic toxicity, with a reported oral LD q in rats of 1580—3300 mg/kg. Dietary doses up to 20,000 ppm adrninistered to rats for two years resulted in no adverse toxicologic or carcinogenic effects. Vanillin is classified as a GRAS substance by EEMA. Consequently, at levels normally found in the human diet, vanillin would present no significant health or carcinogenic risk to humans. 

The carcinogenicity of technical endosulfan was reevaluated in Sprague-Dawley rats using lower doses of endosulfan (Hoechst 1989a). Endosulfan was administered in the diet for 2 years, and no effect on survival was observed in either sex at any dose. Under the conditions of this assay, dietary consumption of doses as high as 3.8 mg/kg/day by females or 2.9 mg/kg/day by males did not result in an increase in the incidence of any neoplastic lesions in these animals. The results from the Hoechst (1989a) bioassay... 

Table 4.1 Glucosinolates that have been studied in relation to their anti-carcinogenic characteristics and their common dietary sources...

Ames, B.N. (1983). Dietary carcinogens and anticarcinogens oxygen radicals and degenerative diseases. Science 221, 1256-1264. 

A 2-year carcinogenicity bioassay of tricresyl phosphate in mice and rats showed no evidence of carcinogenicity in these species (NTP 1994). Doses (consumed in feed) were <37 mg/kg/day in mice and < 15 mg/kg/day in rats. Dietary administration of tributyl phosphate was associated with transitional and squamous cell carcinomas of the bladder in rats after 2 years of exposure at 143.3 mg/kg/day (FMC 1994a). An increased incidence of hepatocellular adenomas in the liver was observed in mice after dietary administration of 455 mg/kg/day tributyl phosphate for 18 months (FMC 1994b). 

For example, 7,12-dimethylbenz[a]anthracene is a particularly potent carcinogen for the mammary gland of young female Sprague-Dawley rats after oral or intravenous administration (25,26), dietary benzo[a]pyrene leads to leukemia, lung adenoma and stomach tumors in mice (27), and either of these hydrocarbons can induce hepatomas in male mice when injected on the first day of life (28). Nevertheless, the mouse skin system has proved to be particularly valuable because of the rapidity of tumor induction, the ease of detection of tumors and because the multi-stage nature of the carcinogenic process was experimentally established in this system. 

Carlton PS, Kresty LA, Siglin JC, Morse MA, Lu J, Morgan C and Stoner GD. 2001. Inhibition of IV-nitrosomethylbenzylamine-induced tumorigensis in the rat esophagus by dietary freeze-dried strawberries. Carcinogen 3 441-446. 

Wattenberg LW. 1975. Effects of dietary constituents on the metabolism of chemical carcinogens. Cancer Res 35(11) 3326—3331. 

Guo JY, Li X, Browning JD Jr., Rottinghaus GE, Lubahn DB, Constantinou A, Bennink M and MacDonald RS. 2004. Dietary soy isoflavones and estrone protect ovariectomized ERalphaKO and wild-type mice from carcinogen-induced colon cancer. J Nutr 134(1) 179—182. 

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