The results of the first large, randomized clinical trial to study the impact of a low-fat diet on breast cancer incidence and mortality are in, and they are encouraging, say researchers.
According to data that will be presented at the 2019 American Society of Clinical Oncology (ASCO) 55th
Annual Meeting in Chicago, a balanced diet that is low in fat and includes daily portions of vegetables, fruit, and grains leads to a 21% lower risk of dying from breast cancer.
Additionally, the risk of death from any other cause after a breast cancer
diagnosis was reduced by 15% for women who followed this diet.
At a press cast ahead of the meeting, lead author Rowan Chlebowski, MD, PhD, FASCO, explained that, given the inconsistent findings of previous studies and the fact that countries with lower fat diets tend to see less instances of breast cancer, the Women’s Health Initiative (WHI) Dietary Modification (DM) clinical trial was created to examine the impact of a low-fat diet on breast cancer incidence and mortality.
From 1993-1998, investigators enrolled 48,835 postmenopausal women ages 50-79 with no previous breast cancer history, from 40 clinical centers across the United States. The women also had diets where 32% or more of their daily calories came from fat.
These participants were then placed randomly into two groups: 29,294 (60%) were assigned to a usual diet comparison group, while 19,541 (40%) were placed in a dietary intervention group with the goal of increasing their daily intake of fruits, vegetables, and grains and reducing their daily fat intake to 20% of their calories.
The comparison group was seen once a year by researchers, while the intervention group was seen at 18 visits over the course of a year, followed by quarterly follow-up visits. The dietary intervention ended after 8.5 years (in 2005), and the trial has followed participants for a median of 19.6 years.
Between 1993 and 2013, 3,374 cases of breast cancer were diagnosed.
In the data being presented at ASCO, researchers have found that the women in the reduced-fat diet group saw more health benefits compared to those in the control group. Most notably, the risk of death from any cause after a breast cancer diagnosis was reduced by 15%, and the risk of death directly from breast cancer was reduced by 21%. Throughout the dietary intervention period of 8.5 years, investigators found 8% fewer breast cancer diagnoses overall.
Chlebowski, of the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center in Torrance, CA, noted that these findings were particularly interesting given that the intervention group did not hit its target goal of reducing fat intake to 20% of total energy, but still managed to see significant benefits while only reducing their intake to 24.5%.
This research shows that dietary changes can significantly influence a woman’s risk of dying from breast cancer, said Cheblowski. “The balanced diet we designed is one of moderation, and after nearly 20 years of follow-up, the health benefits are still accruing.”
Dr. Lidia Schapira, MD, FASCO, ASCO Breast Cancer Expert, was also on the press cast and echoed Chlebowski’s statements with comments that could also ring true for oncology nurses.
“This helps us understand that what we put on our plates matters,” Schapira said. “It helps us, in general, to say that it is worth coaching our patients to put fruits, vegetables and grains on their plates.”
Chlebowski RT, Aragaki AK, Anderson GL, et al. Low-fat dietary pattern and long-term breast cancer incidence and mortality: The Women’s Health Initiative randomized clinical trial. Presented at: ASCO Annual Meeting; May 31-June 4, 2019; Chicago, IL.; Abstract 520.