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The Science Nook on Low-Fat Dietary Pattern and Long-Term Breast Cancer Incidence and Mortality

by Jenna Koroly, MS, RD, CSOWM, CDN

Long-term clinical trials provide valuable information for patients and healthcare providers, while guiding nutrition recommendations. The Women’s Health Initiative Dietary Modification (WHI DM) trial recently came out with continued results of their now 19.6 year cumulative follow-up trial. Below is first the findings from their 2017 publication, and following is the recent findings presented at the 2019 American Society of Clinical Oncology (ASCO) annual meeting.



Low-Fat Dietary Pattern and Breast Cancer Mortality in the Women’s Health Initiative Randomized Controlled Trial

Journal: Journal of Clinical Oncology

The WHI DM enrolled over 48,000 post-menopausal women from 1992-1998. Participants were 50-79 years of age without previous breast cancer and dietary fat intake >32% of total calories measured by food frequency questionnaire (FFQ). They also had mammograms that were not suspicious for cancer.

Participants were divided into two groups: low-fat dietary intervention or usual diet comparison group. The low-fat dietary intervention was designed to reduce fat intake to 20% of total calories and increase intake of vegetables, fruits, and grains. The intervention group attended 18 group sessions led by a certified nutritionist in the first year and 4 times per year afterwards during the 8.5 years intervention. The comparison group received dietary educational materials.

Information about body weight, physical activity, mammography screening, and FFQs was collected. Breast cancer was self-reported and confirmed with medical record review, and cause of death was found in medical record, death certificate review, or reports from participants’ relatives [i].


The authors found:

1. Most women in the dietary intervention group had daily fat consumption of 25% or less, and increased intake of fruits, vegetables, and grains [ii]

2. A significant decrease in deaths after breast cancer in the dietary intervention group during the intervention period (first 8.5 years) and throughout 16.1 year cumulative follow-up

3. A nonsignificant decrease in number of deaths as a result of breast cancer in the dietary intervention group during the intervention period [i]


WHI DM Recent Findings

Recently, continued findings of WHI DM were presented at the 2019 ASCO Annual Meeting the first weekend of this month. Now, after 19.6 years of cumulative follow-up, the significant decrease in deaths after breast cancer continued in the low-fat dietary intervention group, and a significant decrease in deaths from breast cancers was found in the low-fat dietary intervention group [ii].


For the Patient and Caregiver

For both breast cancer prevention and survivorship, focus on increasing vegetables, fruits, and whole grains. To get creative in increasing your whole grain intake, try these recipes from our blog. For postmenopausal women, it may be beneficial to fill most of your plate with a variety of vegetables and fruits, and top with your whole grains, protein, and healthy fats such as olive oil, nuts, and seeds.

For the Healthcare Team

Provide recommendations to postmenopausal women both with and without breast cancer to follow an eating pattern rich in plant-based foods such as vegetables, fruits, and whole grains. Future research to analyze the FFQs of the participants in this trial to see where the 25% of calories from fat is coming from is warranted. For example, to distinguish between saturated and unsaturated fats in order to make more specific dietary recommendations to patients as far as types of fats.


[i] Chlebowski RT, Aragaki AK, Anderson GL, Thomson CA, Manson JE, Simon MS…Prentice RL. (2017). Low-fat dietary pattern and breast cancer mortality in the women’s health initiative randomized controlled trial. J Clin Oncol, 35(25):2919-2925. doi: https://doi.org/10.1200/JCO.2016.72.0326

[ii] Rowan T. Chlebowski, Aaron K Aragaki, Garnet L Anderson, Kathy Pan, Marian L Neuhouser, JoAnn E Manson…Ross L Prentice. (2019). Low-fat dietary pattern and long-term breast cancer incidence and mortality: The Women’s Health Initiative randomized clinical trial. J Clin Oncol, 37. 2019 ASCO Annual Meeting Abstract. Retrieved from http://abstracts.asco.org/239/AbstView_239_253759.html

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