Fiber, Fat, and Colorectal Cancer: New Insight into Modifiable Dietary Risk Factors
Purpose of Review
To review recent data on the role and interactions of fiber and fat as dietary risk factors associated with colorectal cancer (CRC) risk in humans.
Fiber intake shows convincing and linear dose-response negative correlation with CRC risk. Dietary fiber stimulates butyrogenic activity of the gut microbiota, providing high amounts of butyrate that shows extensive anti-neoplastic effects. A high-fat diet promotes CRC risk through stimulated bile acid metabolism, facilitating bile acid conversion by the gut microbiota to tumor-promoting deoxycholic acid. Comprehensive interactions of these microbial metabolites are likely to underlie mechanisms driving diet-dependent CRC risk in different populations, but require further experimental investigation.
Dietary fiber and fat shape the composition and metabolic function of the gut microbiota, resulting in altered amounts of butyrate and deoxycholic acid in the colon. Fiber supplementation and restriction of fat intake represent promising strategies to reduce CRC risk in healthy individuals.
KeywordsColorectal cancer risk Fiber Fat Butyrate Bile acids Gut microbiota
We wish to thank the administration and outpatient clinic and pharmacy staffs at the Alaska Native Medical Center in Anchorage, Alaska, and Manguzi Hospital in Manguzi, KwaZulu-Natal, South Africa, for their support of the project. We also thank all participants for their willingness to participate in the study.
Soeren Ocvirk is supported by the German Research Foundation (Deutsche Forschungsgemeinschaft, 338582098). Stephen JD O’Keefe is supported by the National Institutes of Health (R01 CA204403).
Compliance with Ethical Standards
Conflict of Interest
The authors declare that they have no conflict of interest.
Human and Animal Rights and Informed Consent
Fecal samples, used for preparation of water extracts, were taken during previous studies, where ethical and health research approval was obtained from all institutional review boards of all participating medical centers and health research entities. Informed consent was acquired before enrollment of study participants.
Papers of particular interest, published recently, have been highlighted as: • Of importance •• Of major importance
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