Claim: Higher dietary fiber intake in young women may reduce breast cancer risk

From the perpetual junk science machine known as the Nurses’ Health Study.

The data is not robust enough for the weak statistics to have any meaning. There is no biologic plausibility — i.e., no reason why dietary fiber would have any effect on breast tissue.

The media release is below.

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Higher dietary fiber intake in young women may reduce breast cancer risk
HARVARD T.H. CHAN SCHOOL OF PUBLIC HEALTH

Boston, MA – Women who eat more high-fiber foods during adolescence and young adulthood–especially lots of fruits and vegetables–may have significantly lower breast cancer risk than those who eat less dietary fiber when young, according to a new large-scale study led by researchers at Harvard T.H. Chan School of Public Health.

The study will be published online February 1, 2016 in Pediatrics.

“Previous studies of fiber intake and breast cancer have almost all been non-significant, and none of them examined diet during adolescence or early adulthood, a period when breast cancer risk factors appear to be particularly important,” said Maryam Farvid, visiting scientist at Harvard Chan School and lead author of the study. “This work on the role of nutrition in early life and breast cancer incidence suggests one of the very few potentially modifiable risk factors for premenopausal breast cancer.”

The researchers looked at a group of 90,534 women who participated in the Nurses’ Health Study II, a large long-running investigation of factors that influence women’s health. In 1991, the women–ages 27-44 at the time–filled out questionnaires about their food intake, and did so every four years after that. They also completed a questionnaire in 1998 about their diet during high school. The researchers analyzed the women’s fiber intake while adjusting for a number of other factors, such as race, family history of breast cancer, body mass index, weight change over time, menstruation history, alcohol use, and other dietary factors.

Breast cancer risk was 12%-19% lower among women who ate more dietary fiber in early adulthood, depending on how much more they ate. High intake of fiber during adolescence was also associated with 16% lower risk of overall breast cancer and 24% lower risk of breast cancer before menopause. Among all the women, there was a strong inverse association between fiber intake and breast cancer incidence. For each additional 10 grams of fiber intake daily–for example, about one apple and two slices of whole wheat bread, or about half a cup each of cooked kidney beans and cooked cauliflower or squash–during early adulthood, breast cancer risk dropped by 13%. The greatest apparent benefit came from fruit and vegetable fiber.

The authors speculated that eating more fiber-rich foods may lessen breast cancer risk partly by helping to reduce high estrogen levels in the blood, which are strongly linked with breast cancer development.

“From many other studies we know that breast tissue is particularly influenced by carcinogens and anticarcinogens during childhood and adolescence,” said Walter Willett, Fredrick John Stare Professor of Epidemiology and Nutrition at Harvard Chan School and senior author of the study. “We now have evidence that what we feed our children during this period of life is also an important factor in future cancer risk.”

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2 thoughts on “Claim: Higher dietary fiber intake in young women may reduce breast cancer risk”

  1. “The data is not robust enough for the weak statistics to have any meaning. There is no biologic plausibility — i.e., no reason why dietary fiber would have any effect on breast tissue.”

    I cannot comment on this particular study, as I have not read the paper and I am suspicious of much of the medical statistics – as has been outlined by John Ioannidis’ – but there is good evidence for the potential pathway by which dietary fibre could affect breast cancer through its role in stimulating the immunize via the production of short chain fatty acids in the intestine. See for example:

    NEW FINDINGS CONNECT DIET AND INTESTINAL BACTERIA WITH HEALTHIER IMMUNE SYSTEMS
    Latest News

    http://www.garvan.org.au/news-events/news/new-findings-connect-diet-and-intestinal-bacteria-with-healthier-immune-systems

    And

    Br J Nutr. 2002 May;87 Suppl 2:S221-30.
    The immune-enhancing effects of dietary fibres and prebiotics.
    Schley PD1, Field CJ.

    World J Clin Oncol. 2014 Aug 10; 5(3): 455–464.
    Published online 2014 Aug 10. doi: 10.5306/wjco.v5.i3.455
    PMCID: PMC4127615
    Modification in the diet can induce beneficial effects against breast cancer
    Felix Aragón, Gabriela Perdigón, and Alejandra de Moreno de LeBlanc
    “The population tends to consume foods that in addition to their nutritional values can offer some benefits to their health. There are many epidemiological evidences and research studies in animal models suggesting that diet plays an important role in breast cancer prevention or progression. This review summarized some of the relevant researches about nutrition and cancer during the last years, especially in breast cancer. The analysis of probiotics and fermented products containing lactic acid bacteria in cancer prevention and/or treatment was especially discussed. It was observed that a balance of fatty acids similar to those of traditional Mediterranean diet, the consumption of fruits and vegetables, dietary fiber intake, vitamin supplementation are, along with the intake of probiotic products, the most extensively studied by the negative association to breast cancer risk. The consumption of probiotics and fermented products containing lactic acid bacteria was associated to reduce breast cancer risk in some epidemiological studies. The use of animal models showed the modulation of the host’s immune response as one of the important effects associated to the benefices observed with most probiotics. However; future assays in human are very important before the medical community can accept the addition of probiotic or fermented milks containing lactic acid bacteria as supplements for cancer patients.”

  2. Causality?
    Whatever happened to causality in researching natural phenomena?
    The Nurses’ Health Study is much like a septic tank of raw data; if you look long and hard enough, you are bound to find something in close proximity with something else at some time.

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