A case-control study was conducted to evaluate the association between diet and breast cancer in Korean women.

The eligible subjects consisted of a series of histologically confirmed incident breast cancer patients (n=1063) and non-cancer controls (n=1002) admitted to the departments of surgery at four teaching hospitals located in Seoul, Korea (Seoul National University Hospital, Borame Hospital, Samsung Medical Canter, and Asan medical Center) between 1995 and 2002, from whom blood samples were available. After excluding subjects with a previous history of cancer, hysterectomy or oophorectomy, the final study population consisted of 819 cases and 713 controls. The demographic characteristics and other information were collected by interviewed questionnaire. Dietary information obtained by trained interviewer using food frequency questionnaires.

Women educated more than 12 years (OR=1.9, 95% CI: 1.4~2.7), with a higher body mass index (BMI) (OR= 1.4, 95% CI: 1.1~2.0) and a positive family history of breast cancer among the first degree relatives (OR=2.5, 95% CI: 1.3~4.3) were significant risk factors for breast cancer. The longer the exposure to estrogen during their lifetime, the higher the observed risk of breast cancer was (p for trend<0.001). The risk for breast cancer was increased with frequent consumption of cereals (OR=1.8, 95% CI: 1.8~2.5), potatoes (OR=1.8, 95% CI: 1.4~2.5), nuts and seeds (OR=1.9, 95% CI: 1.1~3.4), mushrooms (OR=1.5, 95% CI: 1.2~1.8), meats (OR=1.5, 95% CI: 1.2~1.9), eggs (OR=1.6, 95% CI: 1.1~2.3) and fish (OR=1.5, 95% CI: 1.2~1.9), whereas the risk decreased with higher intakes of green vegetables (OR=0.6, 95% CI: 0.4~1.0), fruits (OR=0.7, 95% CI: 0.6~0.9) and seaweeds (OR=0.7, 95% CI: 0.5~1.0).

Certain diets (e.g., high fat, high carbohydrate, low vegetable or fruit intake, etc.) were significantly associated with the risk of breast cancer in Korea women, which were similar to the findings in Western countries.