Dietary Patterns and Breast Cancer Risk: A KCPS-II Cohort Study.

Objective: There have been inconsistencies in the evidence for a role of dietary patterns in the development of breast cancer. In this study, we used a large-scale cohort [Korean Cancer Prevention Study-II (KCPS-II)] to examine the association between dietary patterns and breast cancer risk in Korean women.

Materials and methods: The dietary patterns of 14,807 women from the KCPS-II were derived by factor analysis and 135 cases of breast cancer were diagnosed during the follow-up period. Cox proportional models were used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) for the risk of breast cancer.

Results: The following three major dietary patterns were identified: "Korean dietary pattern" (high intake of Kimchi, vegetables, and rice); "sweet dietary pattern" (high intake of soda and sugar); and "new (Western-like) dietary pattern" (high intake of dairy products, eggs, oil, fruits, and bread). After adjusting for potential confounders, neither the Korean (HR for the highest compared with the lowest tertile, 1.04; 95% CI 0.53-2.06) nor the sweet dietary patterns were associated with the risk of breast cancer. In contrast, the new (Western-like) dietary pattern was found to be significantly associated with an increased risk of breast cancer with an HR (95% CI) of 1.01 (0.65-1.60) for the second tertile and 1.61 (1.04-2.50) for the third tertile as compared with the lowest tertile. After stratifying by menopausal status, these effects were only statistically significant among premenopausal women for the third tertile, compared with those in the bottom tertile (HR 1.69; 95% CI 1.06-2.68; p = 0.028). No significant association was observed between the Korean or sweet dietary pattern and breast cancer among either pre- or postmenopausal women.

Conclusion: Our findings revealed that a greater consumption of a new (Western-like) diet was associated with an increased breast cancer risk and consequently offer a potential prevention strategy for Korean women.