Four Healthy Eating Patterns Tied To Lower Mortality In Women With Breast Cancer

Women with invasive breast cancer may reduce their all-cause mortality risk when they follow any of four healthy eating patterns, a recent study suggests.

Researchers examined data on 3,660 women with invasive breast cancer who had diet assessments an average of 2.3 months after diagnosis to pinpoint how closely they followed one of four eating patterns: the American Cancer Society guidelines (ACS), the alternate Mediterranean Diet Index (aMED), the Dietary Approaches to Stop Hypertension (DASH), and the 2015 Healthy Eating Index (HEI).

After a follow-up of 40,888 person-years, a total of 461 women experienced breast cancer recurrence and 655 women died.

When researchers compared women in the lowest and highest quintiles of adherence to each of these diet patterns, they found a significantly lower risk of all-cause mortality for those in the highest quintile for ACS (hazard ratio 0.73), aMED (HR 0.79), DASH (HR 0.76), and HEI (HR 0.77).

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However, the highest quintiles of adherence to these diets were not significantly associated with lower mortality from breast cancer, researchers report in the Journal of the National Cancer Institute: Cancer Spectrum.

"One reason for this might be because diet quality plays a more important role in other diseases such as cardiovascular disease than on breast cancer prognosis and prior studies have shown breast cancer survivors to be at greater risk for CVD as compared to women without breast cancer," said lead study author Isaac Ergas, of the division of research at Kaiser Permanente Northern California and the University of California, Berkeley.

When researchers looked just at non-breast cancer mortality, women in the highest quintiles of adherence to all four diets had a significantly lower risk, with the lowest impact seen for aMED (HR 0.73) and the biggest impact seen for DASH (HR 0.55).

"I believe the take-home message, for now, is that the diet quality needs for breast cancer survivors may be different as compared to women who are thinking only about prevention, and that, we need further research to understand exactly what those differences are," Ergas said by email.

One limitation of the study is that it only measured adherence to different diet patterns shortly after the time of breast cancer diagnosis, and it's possible women's eating habits changed over time. The study population was also predominantly white, and results may not represent what would happen for women from other racial or ethnic backgrounds.

"We know from many large studies that diet can improve overall survival from a number of mechanisms," said Dr. Dawn Hershman, director of breast oncology at the Herbert Irving Comprehensive Cancer Center at Columbia University Medical Center in New York City.

"It can result in lower body mass index, improved blood pressure and cholesterol, less of a risk of diabetes," Dr. Hershman, who wasn't involved in the study, said by email.

From a cohort study, it is not always possible to know if patients who are healthier are more likely to have the diets studied or if the diets themselves cause the improved outcome, Dr. Hershman noted.

"Other studies have examined specific diets and dietary patterns and the results are mixed," Dr. Hershman said. "We know that helping patients maintain a normal body mass index and encouraging regular exercise is beneficial in improving their overall health."

—Lisa Rapaport

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