Once a patient has been diagnosed and treated for breast cancer, the types of food she eats can have a significant impact on her long-term survival.

A new study found that women who consume more high-fat dairy products after being diagnosed with breast cancer are much more likely to die from a relapse several years later.

Cows are capable of producing milk during pregnancy, said lead author of the study, Dr. Candice Kronke . This leads to an increase in the level of estrogen in milk fats. In nature, pregnant cows are only able to produce milk after their calves are born.

While high-fat dairy products tend to contain high amounts of estrogen, dairy products in which fat has been removed – such as skim milk or 1 and 2 percent milk – effectively lower estrogen levels.

The researchers reviewed data on 1,893 women with breast cancer approximately two years before the study began. Each participant completed a food addiction questionnaire, and 1,513 participants completed follow-up questionnaires six years later. Overall, participants were followed up for an average of 12 years.

In the questionnaire, women were asked questions about their consumption of dairy products, their quantities and types. With the answers to these questions, the researchers were able to classify each woman into groups. “In terms of overall dairy consumption, we did not find an overall strong association with cancer,” Kroenke said . “But for women who ate high-fat dairy products, there was an increased risk of dying from breast cancer.”

Research can be important for cancer patients.