Several prominent news outlets have carried stories recently calling on us to eat more fat, especially more saturated fat, saying “fat is good for you.” Yet, in this large multicountry study, women who ate the most fat, and especially the most saturated fat, were more likely to develop breast cancer (BC) than women who ate the least:

Study: Dietary Fat Intake and Development of Specific Breast Cancer Subtypes, Journal of the National Cancer Institute, 9 April 2014

Press Release: Consuming a high-fat diet is associated with increased risk of certain types of BC, Journal of the National Cancer Institute, 9 April 2014

Researchers “prospectively analyzed data from 10,062 breast cancer (BC) patients from the EPIC study with 11.5 years of follow-up. The EPIC cohort study consisted of 337,327 women living in 10 European countries, which creates a heterogeneous cohort both in terms of geography-related dietary fat intake patterns and in terms of molecular subtype.”

The authors conclude, “a high-fat diet increases breast cancer risk and, most conspicuously, that high saturated fat intake increases risk of receptor-positive disease, suggesting saturated fat involvement in the etiology of receptor-positive breast cancer.”

News Summary: High-Fat Diet May Boost Breast Cancer Risk, Study Found Women Who Ate The Most Saturated Fat Were More Likely To Develop Tumors, HealthDay, 9 April 2014

One strength of the new study is its large numbers, said Mia Gaudet, director of genetic epidemiology at the American Cancer Society. The breast cancer subtypes linked with fat intake are common, she said. “The majority of breast cancers in the U.S. and Europe are ER-positive, PR-positive, HER2-negative,” she noted.

Lead author Sabina Sieri, PhD: It’s possible that the high-fat intake raises the levels of the body’s own estrogen, which can stimulate the growth of breast cancer cells.

Gaudet: “If you have a mainly plant-based diet, that is going to help you keep your fat intake low.”

So, dietary fat increases the risk for breast cancer. Yet Time Magazine’s Brian Walsh urges us to “Eat Butter” (7 grams of saturated fat in just 1 tablespoon) and New York Times’ Mark Bittman informs us that “Butter Is Back.” (“Butter is back, and when you’re looking for a few chunks of pork for a stew, you can resume searching for the best pieces — the ones with the most fat.”) Dietary fat has also been shown to increase the risk for prostate cancer. And we know it’s implicated in the development of insulin resistance and diabetes.  There must be some other motive working to push fat besides public health.