For both pre- and postmenopausal breast cancers, the many studies looking on whether dietary fat matters has resulted in no clear conclusions. Now comes a study from Italy suggesting that it does for certain types of breast tumors, including the most common type.
The study suggests that consuming high amounts of total fat, and saturated fats specifically, links to increased risk of breast tumors fueled by the hormones estrogen and progesterone. About three quarters of US breast tumors are estrogen-receptor positive (ER+). The majority of those also grow in response to progesterone.
The increased risk was most pronounced for high amounts of saturated fat, the type of fat from burgers, butter and primarily animal sources.
Here’s the study abstract, published in the Journal of the National Cancer Institute.
This is one study, and it will be added to the body of evidence on breast cancer prevention in AICR/WCRF’s Continuous Update Project (CUP). In the latest CUP report, there was not enough evidence on total dietary fat to make a conclusion for pre- or postmenopausal cancers.
After an analysis of the research, the CUP report found the evidence strong enough to link certain factors to risk. For postmenopausal cancers, for example, alcohol and obesity increase risk; being active and breastfeeding decrease risk.
In this study, the researchers used dietary questionnaires and other data from approximately 337,000 women. The women are part of EPIC, the large European Prospective Investigation into Cancer and Nutrition that spans 10 European countries. After almost 12 years, 10,062 of the women had developed breast cancer.
Then the researchers separated the cancers into whether they were ER+, PR+ or HER2+, tumors that respond to a protein called human epidermal growth factor receptor 2. (Data was not available for all women.)
Compared to the women who were consuming the least saturated fats per day, the women who were eating the highest amounts had a 28 percent increased risk of ER+/PR+ tumors. For those same tumors, the risk was slightly lower but still significant for the highest category of total dietary fat intake compared to the lowest.
This is after adjusting for the women’s weight, age, calories from alcohol and other factors linked to risk.
The mechanisms are unclear. And more research is needed.
You can read more about the findings from the CUP report and steps you can take to prevent breast cancer on our site, Learn More About Cancer.