A prospective analysis of the EPIC cohort, which followed 337,000 European women, found that each 10-gram daily increase in dietary fibre was associated with a 5 percent reduction in breast cancer risk. A meta-analysis of 24 prospective studies confirmed the dose-dependent inverse association. The protective effect was stronger for high-fibre diets established during adolescence, but remained significant for adult dietary change.
The Mechanisms
- Oestrogen excretion: fibre binds oestrogen conjugates in the gut and prevents their reabsorption; high-fibre diets reduce the enterohepatic recirculation of oestrogen and lower circulating oestrogen levels; a meta-analysis of intervention trials confirms that increasing dietary fibre reduces circulating oestrogens in premenopausal women
- Insulin and IGF-1: high-fibre diets reduce post-meal insulin response and reduce circulating IGF-1; insulin and IGF-1 are independent breast cancer risk factors that stimulate cancer cell proliferation
- Gut microbiome and the oestrobolome: certain gut bacteria express beta-glucuronidase that deconjugates excreted oestrogens, allowing reabsorption; high-fibre diets reduce beta-glucuronidase activity and oestrogen reabsorption
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