DIET AND BREAST-CANCER RISK - RESULTS FROM A POPULATION-BASED, CASE-CONTROL STUDY IN SWEDEN

Background: We describe an epidemiologic analytical study of the relat ionship between current diet and breast cancer risk. Method: The study design is a case-control analysis. Cases were recruited from a mammog raphy screening program used within the national health care system; t he control subjects were selected from subjects free of breast cancer in the same population. A total of 380 cases and 525 control subjects, frequency-matched for age, month of mammography, and county of reside nce, were identified. Of these, 265 cases and 432 control subjects wer e included in this analysis. Odds ratios for breast cancer in relation to food and nutrient intake were the main outcome measures. Results: Exposure in the highest quartile of beta-carotene intake gave an odds ratio of 0.6 (95% confidence interval, 0.4 to 1.0). No increased risk was noted with high fat intake. Breast cancer risk was associated with alcohol intake only when alcohol was analyzed in quartiles: odds rati o, 1.6 (95% confidence interval, 1.0 to 2.4) for the highest quartile of intake vs the lowest. Stratified analyses showed that a high fat in take might decrease the protective effect of beta-carotene intake. Ris ks did not change appreciably with adjustment for total energy intake or. known breast cancer risk factors. Conclusions: As in most other st udies, no strong risk factors for breast cancer have been identified i n the current diet. The negative association between breast cancer ris k and beta-carotene intake may be supported by a plausible mechanism, but our finding concerning alcohol should be interpreted cautiously si nce there was no dose-response relationship and the biological mechani sm for a threshold effect at very low levels of consumption is unclear .