,613 women completed dietary and lifestyle questionnaires and height and weight measurements were taken. During a mean follow-up of 16.6 years, 2,503 incident cases of breast cancer were ascertained. Cox proportional hazard models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for the association of meeting each guideline, and number of guidelines met, with breast cancer risk. The two sets of guidelines yielded similar results. Specifically, adherence to all six ACS guidelines was associated with a 31% reduction in breast cancer risk when compared to subjects adhering to at most one guideline (HR 5 0.69; 95% CI 5 0.49-0.97); similarly, adherence to six or seven of the WCRF/AICR guidelines was also associated with a 31% reduction in breast cancer risk (HR 5 0.69; 95% CI 5 0.47-1.00). Under either classification, meeting each additional guideline was associated with a 4-6% reduction in breast cancer risk. These results suggest that adherence to cancer prevention guidelines is associated with a reduced risk of breast cancer.Breast cancer is the most commonly diagnosed cancer among women worldwide. 1 Incidence rates are more than twice as high in developed countries as in developing countries and evidence from migrant studies indicate that environmental and dietary factors play a large role in this disparity. 1-4 Intake of dietary fat, fiber, vegetables and fruit, red and processed meat, and alcohol, have all been extensively studied in relation to breast cancer, but of these, only alcohol intake shows a consistent positive association with breast cancer risk. 5,6

Although epidemiological evidence on the role of active cigarette smoking in breast cancer risk has been inconsistent, recent literature supports a modest association between smoking and breast cancer. This association is particularly observed in women who smoke for a long duration, or who smoke for a long time prior to their first pregnancy. Here, we provide updated results on cigarette smoking and breast cancer risk in the Canadian National Breast Screening Study (NBSS). The NBSS is a large cohort of 89,835 women, aged 40-59, who were followed for a mean of 22.1 years, resulting in the ascertainment of 6,549 incident cases of breast cancer. Cox proportional hazard models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for the association of cigarette smoking variables with breast cancer risk. We found breast cancer to be associated with duration (40 years vs. 0: HR 5 1.57; 95%CI 5 1.29-1.92), intensity (40 cigarettes per day vs. 0: HR 5 1.21; 95%CI 5 1.04-1.40), cumulative exposure (40 pack-years vs. 0: HR 5 1.19; 95%CI 5 1.06-1.13) and latency (40 years since initiation vs. 0: HR 5 1.19; 95%CI 5 1.10-1.53) of cigarette smoking. Number of years smoked prior to first full-term pregnancy was associated with higher risk of breast cancer than comparative years smoked post-pregnancy (among parous women, 5 years pre pregnancy vs. 0: HR 5 1.18; 95%CI 5 1.10-1.26). These results strongly support a role for cigarette smoking in breast cancer etiology and emphasize the importance of timing of this exposure.Breast cancer is the most commonly diagnosed cancer among women in the United States and accounts for nearly onethird of all female cancer diagnoses, and over 20% of female cancer deaths. 1,2 Although not traditionally considered a tobacco-related cancer, many in vitro and in vivo studies implicate tobacco smoke as a potential breast cancer carcinogen. 3 Cigarette smoking has numerous well documented systemic effects and mammary tissue is capable of uptake of many of the tobacco carcinogens routinely found in the circulation of smokers, including polycyclic aromatic hydrocarbons, aromatic amines and N-nitrosamines. 4 Mammary epithelial cells can subsequently metabolize and activate these compounds into electrophilic intermediates capable of DNA damage and adduct formation. 5,6 Smokers have a higher prevalence of these tobacco-related DNA adducts than nonsmokers, and genomic alterations of mammary epithelial cells exposed to tobacco carcinogens resemble those seen in familial breast cancer. 7,8 Moreover, tobacco use increases the frequency of p53 gene mutations in breast tumors to levels consistent with those found in lung cancer. 7 In contrast to this biological plausibility of tobacco smoke as a breast carcinogen, cigarette smoking is also known to have antiestrogenic effects. 9 Given that estrogen is a well-established risk factor for breast cancer, these anti-estrogenic effects of smoking may mask or attenuate its potential carcinogenic effects. 10 Perhaps for this reason, epidemiological...

Adherence to a plant-based diet that limits red meat intake may be associated with reduced risk of breast cancer, particularly in postmenopausal women.