Background: w-3 polyunsaturated fatty acids (PUFA) could play a protective role on the risk of breast cancer; however, little is known about this relation among Mexican women. We evaluated the association between w-3 and w-6 PUFA intake and breast cancer risk by obesity status in Mexican women.Methods: A population-based case-control study was conducted in Mexico, including 1,000 incident breast cancer cases and 1,074 controls matched to cases by age, health care system, and region. Women provided information on health and diet by in-person interview. Body mass index (BMI) measures were used to define overall obesity. Obesity status was categorized as normal weight (18.5 < BMI < 25), overweight (25 BMI < 30), and obese (BMI 30). A conditional logistic regression model was used to assess the association between PUFA and breast cancer risk.Results: Overall, there was no significant association between w-3 PUFA intake and breast cancer risk (P ¼ 0.31). An increased risk of breast cancer was associated with increasing w-6 PUFA intake in premenopausal women [OR ¼ 1.92, 95% confidence interval (CI) ¼ 1.13-3.26; P ¼ 0.04]. A decreased risk of breast cancer was significantly associated with increasing w-3 PUFA intake in obese women (OR ¼ 0.58, 95% CI ¼ 0.39-0.87; P ¼ 0.008) but not in normal weight nor in overweight women (P heterogeneity ¼ 0.017).Conclusions: Obesity status may affect the association between w-3 PUFA intake and breast cancer risk. The underlying mechanisms may be related to decreased inflammation and improved adipokin and estrogen levels induced by w-3 PUFA in adipose tissue in obese women.Impact: Increased intake of w-3 PUFA should be recommended among Mexican women in particular in obese women. Cancer Epidemiol Biomarkers Prev; 21(2); 319-26. Ó2011 AACR.

Strategies need to be identified that will engage women in physical activity programs.

BACKGROUND-Little is known about the relationship between alcohol intake and breast cancer risk among Mexican women. This association may be modified by folate and Vitamin B12.

BackgroundThyroxine (T4) has been positively associated with tumor cell proliferation, while the effect of triiodothyronine (T3) on cell proliferation has not been well-established because it differs according to the type of cell line used. In Mexico, it has been reported that 14.5% of adult women have some type of thyroid dysfunction and abnormalities in thyroid function tests have been observed in a variety of non-thyroidal illnesses, including breast cancer (BC). These abnormalities might change with body mass index (BMI) because thyroid hormones are involved in the regulation of various metabolic pathways and probably by menopausal status because obesity has been negatively associated with BC in premenopausal women and has been positively associated with BC in postmenopausal women.MethodsTo assess the association between serum thyroid hormone concentration (T4 and T3) and BC and the influence of obesity as an effect modifier of this relationship in premenopausal and postmenopausal women, we measured serum thyroid hormone and thyroid antibody levels in 682 patients with incident breast cancer (cases) and 731 controls, who participated in a population-based case-control study performed from 2004 to 2007 in three states of Mexico. We tested the association of total T4 (TT4) and total T3 (TT3) stratifying by menopausal status and body mass index (BMI), and adjusted for other health and demographic risk factors using logistic regressions models.ResultsHigher serum total T4 (TT4) concentrations were associated with BC in both premenopausal (odds ratio (OR) per standard deviation = 5.98, 95% CI 3.01–11.90) and postmenopausal women (OR per standard deviation = 2.81, 95% CI 2.17–3.65). In premenopausal women, the effect of TT4 decreased as BMI increased while the opposite was observed in postmenopausal women. The significance of the effect modification was marginal (p = 0.059) in postmenopausal women and was not significant in premenopausal women (p = 0.22). Lower TT3 concentrations were associated with BC in both premenopausal and postmenopausal women and no effect modification was observed.ConclusionsThere is a strong association between BC and serum concentrations of TT3 and TT4; this needs to be further investigated to understand why it happens and how important it is to consider these alterations in treatment.Electronic supplementary materialThe online version of this article (10.1186/s13058-018-1017-8) contains supplementary material, which is available to authorized users.

The results of this large population-based case-control study indicate an inverse association between circulating vitamin D levels and breast cancer risk among pre- and postmenopausal Mexican women.