Study: Do women who eat a high fiber diet have a lower risk of breast cancer?


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Adolescent and young adult women

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Checked Healthy people with average cancer risk

Checked Previvors

Checked Women under 45


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Some researchers believe that dietary fiber may decrease breast cancer risk by lowering estrogen levels in the blood. However, many previous studies have failed to find a link between fiber consumption and lower breast cancer risk. The current study suggests that consuming high dietary fiber during adolescence and young adulthood may lower breast cancer risk, but more work needs to be done to confirm this finding. In the meantime, everyone is encouraged to eat a variety of high fiber foods for the many well-documented health benefits. (03/08/16)

Contents

At a glance                  Questions for your doctor
Findings               In-depth                
Clinical trials Limitations
Guidelines Resources and references


STUDY AT A GLANCE

This study is about:

The effect of a high-fiber diet on breast cancer risk for young adults.

Why is this study important?  

Researchers think that eating a high-fiber diet may reduce breast cancer risk by reducing estrogen levels in the body. 

Study findings:  

  1. A high-fiber diet during early adulthood (ages 27-44) was associated with lower risk of breast cancer.
  2. A high-fiber diet during adolescence was also associated with lower risk of breast cancer. 

What does this mean for me? 

This study indicates that eating dietary fiber during adolescence and early adulthood may reduce breast cancer risk. More research needs to be done to confirm this finding, because previous studies, which looked at fiber consumption in older women, do not agree with this finding. 

Regardless of its effect on breast cancer risk, incorporating fiber into the diet benefits a healthy lifestyle.  The American Cancer Society guidelines recommend eating foods that are high in fiber.  The Mayo Clinic notes that a diet high in fiber maintains bowel health, lowers cholesterol levels, controls blood sugar levels and helps people to achieve and/or maintain a healthy weight. 

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Expert Guidelines

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:

Questions To Ask Your Health Care Provider

  • How much fiber should I incorporate into my diet?
  • What are good sources of dietary fiber?
  • What are other ways to reduce my breast cancer risk?
  • Can you refer me to a nutritionist?

 

Open Clinical Trials

  • NCT02334085 The Health of Women Study (HOW). This study conducted by Dr. Susan Love is recruiting men and women 18 years and older with and without breast cancer to assess factors including diet that influence the risk of breast cancer. Participation is via online survey.

IN DEPTH REVIEW OF RESEARCH

Study background: 

Previous research found that dietary fiber does not affect breast cancer risk. However, most of these studies involved older women, and did not look at fiber consumption during adolescence or early adulthood, a critical time when exposure to factors that affect estrogen levels may affect breast cancer risk. 

In March 2016, Maryam Farvid and colleagues from the Harvard T.H. Chan School of Public Health and other institutions published a paper in the journal Pediatrics that examined the relationship between dietary fiber intake during adolescence and young adulthood and breast cancer risk later in life.

Researchers of this study wanted to know:

Whether dietary fiber can modify breast cancer risk.  

Population(s) looked at in the study: 

This study involved 90,534 premenopausal women between the ages of 27-44 who were part of the Nurses’ Health Study II cohort. To be a part of this study, the women could not have reported a previous cancer diagnosis (except non-melanoma skin cancer). The women answered questionnaires that asked about their diet from the point the study began, and were resurveyed every four years over a 20-year period.   

This group of women was also asked to complete another questionnaire about their diet during high school; 47,355 women returned this questionnaire. 

Study findings:  

  1. Consuming dietary fiber during early adulthood reduced breast cancer risk. Women who consumed the most fiber (about 25 grams per day) reduced their breast cancer risk the most compared to women who consumed the least fiber (less than 13 grams per day). The women who consumed the most fiber reduced their risk of getting breast cancer by 19%. 
  2. Consuming both soluble fiber (found in peas, beans and apples) and insoluble fiber (found in nuts and wheat bran) reduced breast cancer risk. Women who consumed high dietary soluble fiber had a 14% reduction in breast cancer risk, while women who consumed high dietary insoluble fiber had a 20% reduction in breast cancer risk.
  3. Total dietary fiber intake during adolescence was associated with a lower risk of breast cancer. Women who consumed the most fiber during adolescence had a 16% reduction in breast cancer risk. 

Limitations:

High-fiber foods also contain many other biologically active ingredients—researchers noted that they cannot exclude the possibility that some ingredients other than fiber contributed to lower breast cancer risk. Additionally, the study population was not a random sampling of women in the U.S.; all participants were registered nurses who are a part of the Nurses’ Health Study II cohort. All studies that look at these types of associations may be affected by other factors that researchers were unable to identify or control. The researchers in this study took into account many other factors that could affect breast cancer risk, but they were unable to definitively say that no other factors were involved.

Conclusions:

This study suggests that consuming a diet that is high in fiber during adolescence and early adulthood may reduce breast cancer risk. However, more work needs to be done to confirm this finding. In the meantime, people should be sure to include dietary fiber in their diets regardless of the effect on breast cancer risk, as it is part of a healthy lifestyle. 

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