Western Diets and Breast Cancer Development

Population studies have consistently shown that Western eating patterns such as eating a diet containing large amounts of fatty meat, processed foods, refined carbohydrate, and alcohol are associated with increased risk of breast cancer. However, not all research has been able to show that healthy eating patterns, such as diets high in fruits, vegetables, whole grains, fish are associated with reduced rates of breast cancer.

“It’s likely that the reason not all studies have been able to show that diets containing lots of fruit and vegetables are protective is because the benefits are probably outweighed if energy or calorie intake is above an individuals requirements or if so called ‘unhealthy’ foods, characteristic of Western diets are eaten”, suggests Kellie Bilinski, Westmead Breast Cancer Institute’s Research Dietitian.

These suggestions are supported by findings of a study by Cottet ¹ that show a healthy or Mediterranean pattern is associated with a reduced risk of breast cancer, but only if energy intake remains within recommendations and if ‘‘unhealthy’’ foods are not consumed in large quantities. The study included 2,381 postmenopausal women who were diagnosed with invasive breast cancer over a 9.7-year follow-up period. The study investigated the effects of either a “alcohol/Western” dietary pattern (essentially meat products, French fries, appetizers, rice/pasta, potatoes, pulses, pizza/pies, canned fish, eggs, alcoholic beverages, cakes, mayonnaise, and butter/cream) versus ‘‘healthy/Mediterranean’’ (essentially vegetables, fruits, seafood, olive oil, and sunflower oil). The Western dietary pattern was associated with a 20% increased risk of breast cancer risk, especially when tumours were estrogen receptor-positive/progesterone receptor-positive (ER+/PR+). The ‘‘healthy/Mediterranean’’ pattern on the other hand was associated with 15% fewer breast cancers breast cancer risk, especially when tumors were estrogen receptor-positive/progesterone receptor-negative (ER+/PR-). The researchers concluded, that adherence to a diet comprising mostly fruits, vegetables, fish, and olive/sunflower oil, along with avoidance of Western-type foods, may contribute to a substantial reduction in postmenopausal breast cancer risk.

“The relation between different food components is complex and we don’t completely understand which components might be contributing to or protective against the development of cancer. Results of studies such as those described above suggest that there may be some sort of hormonal interaction between diet and breast cancer development. There are numerous helpful nutrients in fruits, vegetables and wholegrains that might be associated with a decreased risk of breast cancer, such as antioxidants, folate, lignans, and omega-3 fatty acids, whereas components such as trans-fatty acids, alcohol, or being overweight might contribute an increased risk”, concluded Ms Bilinski.

¹ Cottet et al. Postmenopausal brast cancer risk and dietary patterns in the E3N-EPIC Prospective Cohort Study. Am J Epidemiol 2009;170:1257–1267