Major New Analysis: Fiber May Prevent Breast Cancer

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Eating a diet high in fiber (which occurs naturally in vegetables, whole grains, beans and fruit) may protect women against breast cancer, according to one of the largest analyses of the literature published today online in the advance issue of Annals of Oncology.

The research was funded by the World Cancer Research Fund as part of AICR/WCRF’s Continuous Update Project (CUP) (pdf), an ongoing review of cancer prevention research.

The study found that for every 10 grams of fiber consumed daily – slightly less than a cup of beans – the risk of breast cancer was 5 percent lower. Consuming  20 grams of fiber daily would mean a 10 percent lower risk, and so on.

You can read the abstract here.

When comparing women who ate the most fiber to those who ate the least, women who consumed the highest amounts of fiber had a 7 percent lower risk of breast cancer.

For the analysis, researchers at Imperial College in the United Kingdom analyzed the 16 relevant population studies investigating breast cancer incidence and dietary fiber intake.  This analysis builds on a 2007 and 2009 AICR/WCRF review of the literature, which concluded the evidence linking dietary fiber and breast cancer prevention was too limited or inconsistent to make a conclusion. Since 2007, 8 new studies on the topic have been published.

There are several possible explanations as to how dietary fiber may prevent breast cancer, note the authors, including reducing the amount of circulating estrogen. Fiber may also help with weight control, a known risk factor for postmenopausal cancer.

In May 2011, AICR/WCRF’s latest CUP report concluded that there was convincing evidence that dietary fiber protects against colorectal cancer.

The publication of this new analysis of breast cancer and fiber by independent researchers at Imperial College is part of an ongoing process that keeps AICR’s and WCRF’s cancer prevention advice current. These data have been added to the existing CUP database maintained by AICR/WCRF for future review by the AICR/WCRF CUP expert panel.

As part of our Continuous Update Project, the AICR/WCRF CUP expert panel will in the future weigh this new information alongside other evidence, issue its authoritative judgment on the strength of the evidence linking fiber to reduced breast cancer, and decide how it relates to current AICR/WCRF Recommendations for Cancer Prevention. If deemed necessary, the panel will adjust AICR/WCRF’s advice.

In the meantime, we continue to recommend taking a good look at your plate and making sure at least 2/3 of it is filled with plant foods (vegetables, fruits, whole grains and beans) and 1/3 or less with meat and/or dairy foods. This simple, visual approach is called AICR’s New American Plate.

For healthy recipes that help you add more fiber into your diet, visit AICR’s Test Kitchen.


Author: Mya Nelson

Mya R. Nelson is at American Institute for Cancer Research, where she writes about the research in the field.

3 thoughts on “Major New Analysis: Fiber May Prevent Breast Cancer”

  1. Great article! Thank you! In this day and age fiber STILL isn’t given the kudos it deserves. Upping my fiber to 40+ grams a day and eating plant-based helped with weight loss WITHOUT DIETING, and I just feel so much better. Thanks for posting another area of major concern that fiber can help with: breast cancer.

  2. The two figures are mutually exclusive; each relates to a different type of analysis.

    One type of analysis is called the dose-response and here, the research pulled together the findings from 15 studies. Each of these studies analyzed the difference in risk for increments of 10 grams of fiber. This tells you that for every 10 grams of fiber eaten daily (the dose) there is a 5 percent lower risk of breast cancer (the response). So someone who ate 10 grams would have 5 percent lower risk than someone who ate 0 grams. It’s highly unlikely anyone is eating no fiber every day, but this says that every increment of 10 grams links to a 5 percent lower risk.

    The second type of analysis groups people together by how much fiber they typically eat and compares the high range group to the low range group. The researchers looked at the 16 studies that each investigated the link between high versus low dietary fiber intake and breast cancer risk. Here, the analysis did not look at specific amounts of fiber consumption, but pulled together the findings from each study to see that those who ate the most fiber had a 7 percent lower risk of breast cancer than those who ate the least.

  3. How can 20g of fiber daily reduce my risk by 10% if the “women who consumed the highest amounts of fiber had a 7 percent lower risk of breast cancer”?

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