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The associations between plant foods and breast cancer incidence are inconsistent. The objective of this study was to examine prospectively the association between dietary fibre, plant foods and breast cancer, especially the association between plant food intake and oestrogen receptor (ER) alpha- and beta-defined breast cancer. Among women without prevalent cancer from the population-based prospective Malmö Diet and Cancer cohort (n = 15 773, 46-75 years at baseline), 544 women were diagnosed with incident invasive breast cancer during a mean follow-up of 10.3 years. Information on dietary habits was collected by a modified diet history method. ER status of the tumours was determined by immunohistochemistry using tissue microarray. Cox proportional hazards regression estimated hazard ratios (HRs) and 95% confidence intervals (CIs) of breast cancer associated with fibre and 11 plant food groups. High-fibre bread was significantly associated with a decreased breast cancer incidence (HR, 0.75; 95% CI, 0.57-0.98, for highest compared with lowest quintile). The other plant food groups were not significantly associated with breast cancer incidence. There was a tendency for a negative association for high-fibre bread among ERalpha (+) breast cancer (P for trend = 0.06) and ERbeta (+) breast cancer (P for trend = 0.06). Fried potatoes were statistically significantly associated with increased risk of ERbeta (-) breast cancer (P = 0.01). This study suggests that different plant foods may be differently associated with breast cancer, with fibre-rich bread showing an inverse association. We did not observe strong evidence for differences in incidence according to the ERalpha and ERbeta status of breast cancer.

Heterocyclic amines (HAs), formed when meat and fish are cooked at high temperatures, have been linked to mammary gland cancer in rats, and some epidemiological studies indicate increased breast cancer risk by consumption of well-done meat. The epidemiological evidence linking HAs per se to breast cancer is however sparse, especially from prospective studies. Moreover, high-fat diets rich in omega-6 polyunsaturated fatty acids (PUFAs) have produced higher frequencies of HA-induced mammary gland tumors in rats compared to those fed low-fat diets. The aim was to evaluate prospectively if intake of HAs is associated with breast cancer incidence, and if the association is independent of omega-6 PUFA intakes. Among women 50 years or older at baseline from the population-based prospective Malmö Diet and Cancer cohort (n = 11,699), 430 women were diagnosed with incident invasive breast cancer during a mean follow-up of 10.4 years. Information on dietary habits was collected by a modified diet history method. Cox proportional hazards regression estimated hazard ratios (HRs) and 95% confidence intervals (CIs) of breast cancer associated with energy-adjusted intakes of HAs and omega-6 PUFA. Intakes of HAs were not associated with breast cancer incidence (HR, 0.94; 95% CI, 0.69-1.28, for highest compared to lowest quintile). In individuals with low HA intakes, a significant increased risk was observed among those with high intakes of omega-6 PUFAs. In conclusion, intakes of HAs are not associated with breast cancer incidence in this Swedish cohort, but dietary patterns very high in omega-6 PUFA may promote breast cancer development.

Objectives: The aim of this study was to examine the variation of enterolactone from fasting and non-fasting blood of middle-aged healthy women eating a normal diet to determine the usefulness of a single sample in epidemiological studies., Subjects and Methods: Twenty-six women born between 1940 and 1950 were recruited within the Malmö Diet and Cancer cohort. Three non-fasting and two overnight fasting samples were collected from each individual during a 5-week period. Twenty-one participated in all measurements. Enterolactone concentrations were analyzed by time-resolved fluoroimmunoassay., Results: The within-subject and between-subject variations (coefficient of variations, CV) were estimated to 59 and 89% respectively for fasting samples and 71 and 67% for non-fasting samples. The intraclass correlation coefficients (ICC) were estimated to 0.66 (95% confidence interval (CI) 0.35-0.84) for fasting and 0.48 (95% CI, 0.22-0.72) for non-fasting samples., Conclusions: Although the estimated ICC for blood samples was moderate, it indicates that enterolactone levels of both fasting and non-fasting blood samples should be useful in future projects within the Malmö Diet and Cancer cohort.