Breast cancer survivors see cardiovascular benefit from heart-healthy diet

Kaiser Permanente Pathways Study following women diagnosed with breast cancer allows researchers to study effect of diet over time

Women who had a heart-healthy diet at the time of their breast cancer diagnosis had a lower risk of going on to develop heart disease, new Kaiser Permanente research shows.

The study, published in JNCI Cancer Spectrum, highlights the importance of educating breast cancer survivors about heart health. Breast cancer is the most commonly diagnosed cancer in women in the United States, but heart disease is the most common cause of death. The risk of heart disease is even higher in breast cancer survivors. This is thought to be because some cancer therapies can cause heart damage. Also, both diseases share similar risk factors, such as poor diet, obesity, and smoking.

“Many people are not aware that breast cancer survivors have a higher risk of developing heart disease than women who have not had breast cancer,” said lead author Isaac Ergas, PhD, MPH, MFA, a staff scientist at the Kaiser Permanente Division of Research. “Since diet can improve heart health, we felt it was important to see if diet quality was related to future risk of heart disease in women diagnosed with breast cancer.”

The research team analyzed data from the Pathways Study, one of the largest U.S. studies to begin following women from the time of their breast cancer diagnosis. They looked at 3,415 women who had been diagnosed with invasive breast cancer at Kaiser Permanente Northern California between 2005 and 2013 and followed through 2021. All the participants had completed a diet questionnaire when they entered the Pathways Study.

The study evaluated 5 healthy dietary patterns: the Dietary Approaches to Stop Hypertension (DASH) Eating Plan, which is recommended to promote heart health; the American Cancer Society recommended diet for cancer survivors; a healthy plant-based diet; the 2020 Healthy Eating Index; and the alternate Mediterranean diet.

The study found that women whose food choices at the time of their breast cancer diagnosis were most similar to those recommended by the DASH Eating Plan had the lowest risk of developing heart disease. These women had a 47% lower risk of heart failure, a 23% lower risk of arrhythmia (an irregular heartbeat), a 23% lower risk of cardiac arrest, a 21% lower risk of valvular heart disease, and a 25% lower risk of developing a blood clot than women whose food choices were least like those recommended by DASH.

“It is exciting to see the results of this excellent work that empowers our oncologists to recommend evidence-based lifestyle medicine recommendations,” said Tatjana Kolevska, MD, chair of The Permanente Medical Group Medical Oncology and Hematology.

The researchers also looked at whether the type of chemotherapy treatment a woman received modified the effect of the DASH diet on heart health. They found that in women who were treated with an anthracycline — a type of chemotherapy that can cause heart damage —  those with a diet most similar to DASH had a lower risk of developing or dying from cardiovascular disease than those whose diets were less like the DASH diet. This difference was not observed in women on other types of chemotherapy treatments.

The DASH Eating Plan recommends eating vegetables, fruits, and whole grains; including fish, poultry, beans, nuts, vegetable oils, and fat-free or low-fat dairy products; and limiting sugar-sweetened beverages, sweets, and foods high in saturated fats.

“Our study is one of the few studies that has taken a deep dive into the effect of diet on cardiovascular disease risk in breast cancer survivors,” said senior author Marilyn Kwan, PhD, a research scientist at the Division of Research. “Our findings highlight how important it is that we continue to talk to breast cancer survivors about diet quality, not only to reduce their risk of a breast cancer recurrence but to reduce their risk of developing cardiovascular disease.”

Ergas said his team will soon launch a pilot study of a new tool for assessing cancer patients’ dietary patterns. “If this tool works well,” he said, “it’s something that doctors could potentially use in the clinic to assess whether a patient has a healthy diet and to make recommendations for improving their heart health.”

The study was funded by the National Cancer Institute.

Co-authors include Richard K. Cheng, MD, MS, of the University of Washington; Janise M. Roh, MSW, MPH, Lawrence H. Kushi, ScD, Carlos Iribarren, MD, MPH, PhD, Mai Nguyen-Huynh, MD, MAS, Jamal S. Rana, MD, PhD, Cecile A. Laurent, MS, Valerie S. Lee, MHS, and Charles P. Quesenberry, PhD, of the Division of Research; Jacob K. Kresovich, PhD, MPH, of the Moffitt Cancer Center and Research Institute; and Eileen Rillamas-Sun, PhD, MPH, of the Fred Hutchinson Cancer.

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About the Kaiser Permanente Division of Research

The Kaiser Permanente Division of Research conducts, publishes and disseminates epidemiologic and health services research to improve the health and medical care of Kaiser Permanente members and society at large. It seeks to understand the determinants of illness and well-being, and to improve the quality and cost-effectiveness of health care. Currently, DOR’s 600-plus staff is working on more than 450 epidemiological and health services research projects. For more information, visit divisionofresearch.kaiserpermanente.org or follow us @KPDOR.