Every 10 gram per day increase in soluble fiber intake was associated with a 26% reduction in the risk of breast cancer, but no such effect was observed for insoluble fiber, according to findings published in the Annals of Oncology.
When the researchers looked at the different types of fibers, they only observed an inverse relationship for soluble fiber, and not for insoluble fiber, fruit fiber, vegetable fiber or cereal fiber.
In addition, the greatest risk reduction was observed for fiber intakes over 25 grams per day, said the researchers.
“Achieving such a level of fiber intake may be a challenge in many populations, nevertheless, considering the few dietary risk factors that have been established for breast cancer and the relatively low or moderate fiber intake in many populations, diets with high intake of plant-based foods rich in fiber could have an impact in the prevention of breast cancer,” wrote the researchers.
Fiber benefits
Increased intakes of fiber have been linked to a range of health benefits. Researchers from the US National Cancer Institute reported last year that increased dietary intakes of fiber are associated with lower risks of dying from cardiovascular, infectious, and respiratory diseases (Archives of Internal Medicine, doi:10.1001/archinternmed.2011.18).
The message has filtered through to consumers, with a 2008 International Food Information Council survey reporting that 77% of people are proactively trying to consume additional fiber.
Meta-analysis
For the new meta-analysis, the England-based researchers said that several mechanisms may explain the observations, with a role for fiber in binding estrogen or reducing the absorption of the hormone. Fiber may also slow down the speed at which the stomach empties, and this would decrease the absorption of glucose, and reduce the secretion of insulin.
“High intake of dietary fiber may also reduce the risk of overweight/obesity, which is an established risk factor for postmenopausal breast cancer,” they added, “however, the association was also present in studies that adjusted for body mass index or weight, suggesting an association independent of overweight/obesity.”
“Further studies of specific types of fiber and breast cancer risk stratified by hormone receptor status could clarify the biological mechanism(s) behind this finding,” they concluded.
Source: Annals of Oncology
Published online ahead of print, doi: 10.1093/annonc/mdr589
“Dietary fiber and breast cancer risk: a systematic review and meta-analysis of prospective studies”
Authors: D. Aune, D.S.M. Chan, D.C. Greenwood, A.R. Vieira, D.A.N. Rosenblatt, R. Vieira, T. Norat