High intake of meat, particularly red and processed meat, has been associated with an increased risk of a number of common cancers, such as breast, colorectum, and prostate in many epidemiological studies. Heterocyclic amines (HCAs) are a group of mutagenic compounds found in cooked meats, particularly well-done meats. HCAs are some of most potent mutagens detected using the Ames/ salmonella tests and have been clearly shown to induce tumors in experimental animal models. Over the past 10 years, an increasing number of epidemiological studies have evaluated the association of well-done meat intake and meat carcinogen exposure with cancer risk. The results from these epidemiologic studies were evaluated and summarized in this review. The majority of these studies have shown that high intake of well-done meat and high exposure to meat carcinogens, particularly HCAs, may increase the risk of human cancer.
Background: Soy food is a rich source of isoflavones-a class of phytoestrogens that has both antiestrogenic and anticarcinogenic properties. Objective: The objective was to evaluate the association of adolescent and adult soy food intake with breast cancer risk in a cohort of 73,223 Chinese women who participated in the Shanghai Women's Health Study. Design: A validated food-frequency questionnaire was used to assess usual dietary intake during adulthood and adolescence. After a mean follow-up of 7.4 y, 592 incident cases of breast cancer were identified for longitudinal analyses by using Cox regressions. Results: Adult soy food consumption, measured either by soy protein or isoflavone intake, was inversely associated with the risk of premenopausal breast cancer, and the association was highly statistically significant (P for trend , 0.001). The multivariate-adjusted relative risks (RRs) for the upper intake quintile compared with the lowest quintile were 0.41 (95% CI: 0.25, 0.70) for soy protein intake and 0.44 (95% CI: 0.26, 0.73) for isoflavone intake. High intake of soy foods during adolescence was also associated with a reduced risk of premenopausal breast cancer (RR: 0.57; 95% CI: 0.34, 0.97). Women who consumed a high amount of soy foods consistently during adolescence and adulthood had a substantially reduced risk of breast cancer. No significant association with soy food consumption was found for postmenopausal breast cancer. Conclusion: This large, population-based, prospective cohort study provides strong evidence of a protective effect of soy food intake against premenopausal breast cancer.
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