Dietary patterns and risk of breast cancer in Chinese women: a population-based case-control study.

BACKGROUND: The incidence rate of breast cancer has markedly increased in recent years in China, yet the association of breast cancer with dietary patterns such as a Chinese traditional diet has not been studied. We aimed to examine this association among women from the Jiangsu Province of China.

METHODS: In this case-control study, we used the data from local population-based cancer registry agency to recruit newly diagnosed patients with primary breast cancer as cases. We selected the controls from the general population of the same residence as cases, whom we frequency matched by about 5 years. We used a validated food frequency questionnaire to assess dietary intake using face-to-face interviews. We identified dietary patterns doing a principal component analysis. We estimated multivariate odds ratios (ORs) and 95% CIs for quartiles of component scores (ie, factor scores ranging from low [first quartile] to high [fourth quartile]) for each dietary pattern using unconditional logistic regression. This research has been approved by the ethical committee of Jiangsu Provincial Center for Disease Control and Prevention. Participants were well informed of the whole procedure and all gave informed consent.

FINDINGS: Between November, 2013, and January, 2015, we recruited 818 cases and 935 controls. Four dietary patterns were identified: salty (salt, oil, monosodium glutamate, soy sauce, sugar, soft drinks, and pickles), vegetarian (soy, nuts, fruits, vegetables, aquatics, and milk), sweet (soft drinks, sugar strengthened beverages, fried food, cakes, milk, coffee, and fresh juice) and Chinese-traditional (meat, eggs, rice or flour, aquatics, vegetables, and poultry). After adjusting for confounders, we found the Chinese-traditional pattern to be robustly associated with a decreased risk of breast cancer among both pre-menopausal and post-menopausal women (fourth vs first quartile: OR among premenopausal women was 0·47, 95% CI 0·29-0·76, ptrend=0·004; OR among postmenopausal women was 0·68, 0·48-0·97, ptrend=0·006). Women with a high intake of the sweet pattern showed a decreased risk of breast cancer (fourth vs first quartile: OR for pre-menopausal women was 0·47, 0·28-0·79; OR for post-menopausal women was 0·68, 0·47-0·98). No significant association was observed between salty or vegetarian patterns and breast cancer.

INTERPRETATION: These findings indicate that Chinese-traditional pattern and sweet pattern might favourably affect the risk of breast cancer in Chinese women.

FUNDING: World Cancer Research Fund (2011/RFA/473).