Study: A low-fat diet may decrease postmenopausal breast cancer deaths

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Post-menopausal women with no breast cancer diagnosis

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Checked Healthy people with average cancer risk

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Research reported at the 2019 annual meeting of the American Society of Clinical Oncology establishes a link between dietary fat intake and its impact on postmenopausal women’s risk of dying from breast cancer. (6/13/19)


At a glance                  Questions for your doctor
Findings               Limitations              
Guidelines Resources and reference


This study is about:

how a balanced, low-fat diet significantly lowers the risk of dying from breast cancer in postmenopausal women.

Why is this study important?

This trial is the first randomized clinical trial to show that a healthy diet can reduce the risk of death from breast cancer.

Study findings:

In 1993, the Women’s Health Initiative Diet Modification Trial looked at almost 50,000 postmenopausal women with no history of breast cancer. Participants were women of multiple races, ethnicities and varying ages. They were randomized to one of two diets.

1. Women in the usual-diet group got about 30 percent (1/3) of their daily calories from fat.

  • This group had one follow-up visit per year.

2. Women in the low-fat diet group were asked to reduce their fat intake to 20 percent (1/5) of daily calories. 

  • They were also encouraged to eat more vegetables, fruits and whole grains.
    • 5 servings of vegetables and fruits every day.
    • 6 servings of whole grains every day.
  • This group also had 18 small-group support sessions and quarterly follow-up.

Women in the low-fat diet group stuck to the diet for about 8½ years. Most of them increased their intake of fruits, vegetables and whole grains and cut their daily fat intake to 25 percent or less, although most did not reach the 20 percent goal. Women in this trial were followed for 20 years. During that time, over 3,000 (15 percent) women developed breast cancer.

Compared to women in the usual-diet group, women in the low-fat diet group had:

  • a 21 percent lower risk of death from breast cancer.
  • a 15 percent lower risk of death from any cause.

Women with additional risk factors—a waist circumference greater than 35 inches (88 cm), high blood pressure or taking drugs to reduce blood pressure, elevated cholesterol, or a history of diabetes—had greater benefit from a low-fat diet.

Women with three or four risk factors who followed the low-fat diet decreased their risk for death from breast cancer by almost 70 percent.

What does this mean for me?

It is important to understand that a low-fat diet did not significantly reduce the risk of developing breast cancer.  However, for postmenopausal women, a low-fat diet significantly reduced the risk of dying from breast cancer or other causes. It also dramatically reduced the risk of breast cancer-related death for women who had other health risk factors.

This study did not look at how a low-fat diet affects the risk of dying from breast cancer among:

  • premenopausal women
  • women who are at high risk for breast cancer

Therefore, it is unclear if a low-fat diet would have the same protective effects in these women.

You may have different nutritional needs if you are pregnant, nursing or in treatment; it is important to discuss these requirements with your doctor.


Most women in the low-fat diet group were unable to achieve the recommended reduction of fat in their diets and fell short of the targeted number of whole-grain servings.  The degree to which women stuck to the diet relied primarily on self-reported eating habits.  Finally, given the 20-year follow-up period, differences other than diet may have existed between the two groups.


A reduction in dietary fat and an increase in fruits, vegetables and whole grains can result in important health outcomes.  It can lower the risk of death from breast cancer by 21 percent and reduce the risk of death from any cause by 15 percent. Importantly, for women with other risk factors it can decrease risk of death from breast cancer by almost 70 percent.

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(Posted 6/13/19)

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Expert Guidelines

Fat is an important part of a healthy diet, but experts recommend limiting daily fat intake. Many guidelines provide tips on limiting “bad fats,” which are most often found in processed and fast foods.

The American Cancer Society recommendations on nutrition and physical activity for cancer prevention include:

  • Achieve and maintain a healthy weight throughout life.
  • Adopt a physically active lifestyle.
  • Consume a healthy diet with an emphasis on plant-based foods
  • Limit the amount of processed and red meats:
    • Eat at least 2.5 cups of vegetables and fruits a day.
    • Chose whole grains instead of refined grain products.
    • Drink no more than 1 alcoholic drink per day (women).

Other experts also provide guidelines for nutrition and health, including:

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Questions To Ask Your Health Care Provider

  • What is a good, balanced diet for me?
  • What is a healthy body weight given my age, size and health?
  • Can you refer me to a nutritionist?
  • Are there any activities that I should begin or avoid?

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