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

Summary

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)

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

Relevance

This article is most relevant for Adolescent and young adult women

Relevance Rating Details

Relevance: Medium-High

Strength of Science: Medium

Media Ratings

Did you see the media coverage of this article?

See all media ratings.

How we rated the media

Who covered this study?

NPR

A diet high in fiber may help protect against breast cancer
This article rates 4.5 out of 5 stars

CBS News

Teen eating habits may help cut breast cancer risk
This article rates 4.5 out of 5 stars

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Contents

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


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 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. 

Posted 3/18/16

Share your thoughts on this XRAYS article by taking our brief survey. 

References

Farvid MS, Eliassen H, Cho E, et al. “Dietary Fiber Intake in Young Adults and Breast Cancer Risk.” Pediatrics. 137 (3), March 2016.   

Kushi, LH, Doyle, C, McCullough, M, et al., “American Cancer Society guidelines on nutrition and physical activity for cancer prevention,” CA: A Cancer Journal for Clinicians. 62 (1), p. 30-67, January/February 2012. 

Mayo Clinic Staff. “Dietary fiber:  Essential for a healthy diet.”

Disclosure

FORCE receives funding from industry sponsors, including companies that manufacture cancer drugs, tests and devices. All XRAYS articles are written independently of any sponsor and are reviewed by members of our Scientific Advisory Board prior to publication to assure scientific integrity.

This article is relevant for:

Adolescent and young adult women

This article is also relevant for:

previvors

healthy people with average cancer risk

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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 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. 

Expert Guidelines
Expert Guidelines

The American Cancer Society (ACS) guidelines on exercise, nutrition and weight for cancer prevention recommend the following: 

Diet and nutrition

  • Follow a healthy eating pattern, including:
    • foods that are high in nutrients in amounts that help you acheive and maintain a healthy body weight.
    • a variety of vegetables, fiber-rich legumes (beans and peas) and whole fruits in a variety of colors. Consume at least 2½ to 3 cups of vegetables and 1½ to 2 cups of fruit each day, depending on your calorie requirements. 
    • whole grains rather than refined grains. At least half of the grains you eat should be whole grains. 
  • A healthy eating pattern that limits or does not include:
    • red and processed meats.
    • sugar-sweetened beverages. 
    • highly processed foods and refined grain products.
  • It is best not to drink alcohol. People who choose to drink alcohol should:
    • have no more than 1 drink per day (women) or 2 drinks per day (men).

Exercise

  • Exercise regularly.
    • Adults should get at least 150 minutes of moderate-intensity activity (equal to a brisk walk) or 75 minutes of vigorous activity (heart rate is increased, breathing is faster and you are sweating) each week, preferably spread throughout the week.
    • Physical activity has been shown to lower the risk of several types of cancer, including breast, endometrial, and colon. It also reduces the risk of other serious diseases including diabetes and heart disease.

Weight

  • Achieve and keep a healthy weight.
    • Being overweight or obese is a risk factor for many cancers, including breast, colon, endometrial and pancreatic. You can control your weight through regular exercise and healthy eating.

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

Updated: 07/19/2022

Questions To Ask Your Doctor
Questions To Ask Your Doctor

  • 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
Open Clinical Trials

The following are studies focused on nutrition and cancer prevention. 

Multiple cancers

Breast cancer

Colorectal cancer

Visit our Featured Research Page and Research Search and Enroll Tool to find additional studies enrolling people with or at high risk for cancer.

Updated: 05/28/2023

Find Experts
Find Experts

The following resources can help you locate a nutritionist near you or via telehealth

Finding nutritionists

  • You can find a registered dietician in your area through Eatright.org, the website for the Academy of Nutrition and Dietetics. Search for nutritionists by specialty, including "cancer," "weight management" and "heart health."


Related experts

  • The YMCA has a free program called Livestrong at the YMCA. This program includes a free 12-week membership and fitness training with certified exercise experts. You can search by zip code for a program near you.  


Other ways to find experts

  • Register for the FORCE Message Boards and post on the Find a Specialist board to connect with other people who share your situation. 
  • The National Cancer Institute (NCI)-designated comprehensive cancer centers have specialists to manage the symptoms and side effects from cancer prevention or treatment. 
  • FORCE partners with Savor Health® to provide free, personalized, evidence-based nutrition support 24/7 and “on-demand" through their text-based Intelligent Nutrition Assistant (Ina®). You can subscribe here. 

 

Updated: 11/20/2023

Related Resources
Related Resources

The following resources focus on nutrition and cancer. 

The following resources focus on nutritional safety.

 

Updated: 11/20/2023

Who covered this study?

NPR

A diet high in fiber may help protect against breast cancer This article rates 4.5 out of 5 stars

CBS News

Teen eating habits may help cut breast cancer risk This article rates 4.5 out of 5 stars

Huffington Post

High-fiber diet may help lower breast cancer risk This article rates 4.0 out of 5 stars

Glamour

Reason 283 to have a salad for lunch today: Fiber Is shown to lower your breast cancer risk This article rates 4.0 out of 5 stars

Health Day

Girls who eat more fiber may face lower breast cancer risk later: Study This article rates 4.0 out of 5 stars

Teen Vogue

This Is what you need to eat as a teen to help prevent breast cancer This article rates 4.0 out of 5 stars

How we rated the media

Back to XRAY Home

Article Rating Details

NPR:  A Diet High In Fiber May Help Protect Against Breast Cancer
Rating: 4.5 Stars

  • This media article was well-written. 
  • This media article gave the average amount of fiber the women consumed. This is incorrect, the research article did not report the average amount of fiber, it reported the median amount of fiber the women consumed.

CBS News: Teen Eating Habits May Help Cut Breast Cancer Risk
Rating: 4.5 Stars

  • This media article contains many great sources that have good commentary that puts the results of this research study into perspective. 
  • This media article said that breast cancer risk was 12-19% lower among women who ate more dietary fiber in their youth. Because the beginning of this article emphasizes the results relating to high school girls, it should be clarified that the 12-19% refers to the risk reduction for young adults, not high school girls. 

 

Huffington Post:  High-Fiber Diet May Help Lower Breast Cancer Risk
Rating: 4 Stars

  • This media article was well-written, overall.
  • This media article did not include any comments from an outside source.
  • This media article did not mention any limitations of the research. However, it is good that they made the point regarding the results of this study being an association and not a cause and effect relationship, meaning that researchers do not really understand if fiber is directly causing the reduced breast cancer risk.

 

 

Glamour:  Reason 283 to Have a Salad for Lunch Today: Fiber Is Shown to Lower Your Breast Cancer Risk
Rating: 4 Stars

  • This media article did not include any comments from sources who were not involved in the study.
  • This media article did not mention any limitations of the study.

Health Day:  Girls Who Eat More Fiber May Face Lower Breast Cancer Risk Later: Study Rating: 4 Stars

  • This media article was well-written. 
  • This media article did not directly interview any sources.
  • It was good that this media article talked about how fiber should be included in diets because of its other health benefits even though this study does not prove that fiber helps prevent breast cancer
  • This media article did not mention other study limitations.

Teen Vogue:  This Is What You Need to Eat as a Teen to Help Prevent Breast Cancer Rating: 4 Stars

  • While the results suggest that eating more fiber when you are young reduces breast cancer risk, it is not definitive; more work needs to be done. The headline and lede of this media article are slightly exaggerated as it presents it as: eat fiber to reduce breast cancer risk. 
  • The 12-19% breast cancer risk reduction the media article reports should be attributed to young adults (aged 27-44) not high school girls.

 

 

Study Rating Details

Relevance: Medium-High

  • This research is most relevant to young women. 
  • It is possible to modify dietary fiber levels. There are other benefits to eating a high-fiber diet. 
  • More research will be needed to confirm that a high fiber diet lowers breast cancer risk. 

Strength of Science: Medium

  • This research study is a large study that looked at how much fiber young women ate and whether that was associated with breast cancer development.
  • Researchers also looked at whether fiber eaten during adolescence was associated with breast cancer development. To answer that question, the researchers had to ask the women to remember what they ate back in high school, which would be impossible for women to answer with 100% accuracy.
  • While the researchers tried to control for other factors to the best of their ability, they cannot definitively say that there was no other factor that may be responsible for the lowered risk of breast cancer they see. 
  • This is relevant to young women --the results suggest that eating high amounts of fiber when a woman is young may reduce breast cancer risk. However, they did not look at any genetics, so it is unknown if BRCA or another genetic mutation may alter this effect.