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Low-fat diet reduces risk for breast cancer death among postmenopausal women
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Postmenopausal women reduced their breast cancer mortality risk by adopting a low-fat diet that included increased consumption of vegetables, fruits and grains, according to results from a randomized Women’s Health Initiative clinical trial scheduled for presentation at ASCO Annual Meeting.
“The impetus for a study of dietary fat intake and eating patterns came a quarter of a century ago, when we noticed country-to-country differences in fat intake and breast cancers; countries with low fat intake had lower breast cancer frequency. The question was, were these factors related?” study author Rowan T. Chlebowski, MD, PhD, FASCO, chief of the division of medical oncology and hematology at Harbor-UCLA Medical Center and researcher at the center’s Los Angeles Biomedical Research Institute, said during a press cast. “The observational studies have provided mixed results, and so this randomized clinical trial started as a component of the Women’s Health Initiative.”
Chlebowski and colleagues evaluated the influence of a low-fat diet on breast cancer incidence and outcomes among 48,835 postmenopausal women aged 50 to 79 years seen at 40 participating U.S. centers. Participants had no history of breast cancer and consumed a diet in which fat comprised 32% or more of total daily calories.
Between 1993 and 1998, the researchers randomly assigned the women to a usual-diet control group (60%) or to a dietary intervention group (40%), in which the goal was to decrease fat intake to 20% of energy or less and include one daily serving or more of a vegetable, fruit and grain. In the usual-diet control group, fat accounted for 32% or more of participants’ daily calories.
Women followed the balanced, low-fat intervention diet for about 8.5 years.
Results showed the intervention resulted in a significant decrease in daily fat intake to 25% or less of daily calories — most women did not reach the 20% goal — as well as increased consumption of fruit, vegetables and grains, with modest (3%) average weight loss (all P < .001).
The intervention group incurred 8% fewer breast cancers than the control group during the dietary intervention and fewer breast cancer deaths, but the difference in these rates was not significant.
However, the intervention group demonstrated a 15% reduced risk for death of any cause after a breast cancer diagnosis, with decreases in risk during the intervention (HR = 0.65; 95% CI, 0.45-0.95) and through a cumulative median follow-up of 16.1 years.
With long-term, cumulative follow-up of 19.6 years and 3,374 cases of breast cancer diagnosed among participants, the intervention group continued to demonstrate significant decrease in deaths after breast cancer (n = 1,011; HR = 0.85; 95% CI, 0.74-0.96), and showed a significant reduction in deaths of breast cancer (n = 383; HR = 0.79; 95% CI, 0.64-0.97).
Additionally, metabolic syndrome score identified a subgroup of women at high risk for death from breast cancer who were more likely to benefit from the dietary intervention. The 9.3% of women with three or four components of metabolic syndrome had a statistically significant 69% (HR = 0.31; 95% CI, 0.14-0.69) reduced risk for breast cancer mortality.
“Adoption of a low-fat dietary pattern reduces the risk for death from breast cancer in postmenopausal women,” Chlebowski said. “It’s a diet we feel is achievable by many, because it represents dietary moderation and was achieved by 19,000 women in the study.” – by Jennifer Byrne
Reference:
Chlebowski RT, et al. Abstract 520. Scheduled for presentation at: ASCO Annual Meeting; May 31-June 3, 2019; Chicago.
Disclosures: NCI provided funding for this study. Chlebowski reports consultant/advisory roles with Amgen, AstraZeneca, Genentech, Novartis and Pfizer; speakers bureau roles with AstraZeneca and Novartis; and patents, royalties and other intellectual property, stock and ownership interests with Metastat. Please see the abstract for all other authors’ relevant financial disclosures.
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Kelly Hogan , MS, RD, CDE
These findings emphasize the importance of following a plant-based diet that is rich in fruits, vegetables and whole grains. They also underscore the importance of including diet and nutrition in a care plan for a patient with breast cancer.
Thinking about diet from diagnosis to treatment and beyond is important. This study shows how helpful it is to make dietary changes if you need to make them, and to continue to think about the quality of your diet after treatment and during survivorship. Nutrition should always be discussed with patients with breast cancer; that is why it is so important to have a registered dietitian as part of the health care team.
Plant-based diets have been shown to reduce risk for chronic disease, certain cancers such as breast cancer and promote overall health. Eating a variety of colorful fruits and vegetables, whole grains, legumes, nuts and seeds have positive effects on health because these foods have anti-inflammatory properties, are good sources of a variety of vitamins, minerals and fiber. Overall, it’s always important and much more useful to focus on all the foods patients with breast cancer should eat more of, rather than focusing on what they can’t eat.
Mount Sinai Hospital
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Lidia Schapira, MD, FASCO
This study helps us to understand that what we put on the plate matters.
For a long time, primary care and cancer doctors have been trying to answer these questions, which are foremost in the minds of many women who have had or are at risk for breast cancer. This is a prevention study, so it doesn’t help us in counseling women after breast cancer, but it demonstrates that it is worth it to encourage our patients to put fruits, vegetables and grains on their plates. This is not easy; Dr. Chlebowski said they did not reduce dietary fat as much as they had intended, but to the extent they did, they showed there was a health advantage.
This is not to say that this will allow us to give personalized, precise information to every person; many factors influence the development of breast cancer and other malignancies. However, for the time being, it is worth it for us to stick to this message of prevention — that postmenopausal women who take the time to think about and plan their diets will be taking an important step toward improving their health.
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