That was the view of Dr Scott Bultman, associate professor, Department of Genetics at the University of North Carolina. He believes the heterogeneity of study participants, the differences in their gut microbiota and the use of different fibre sources (which are fermented by gut microflora into different metabolites) have all made results the subject of controversy.
To complicate matters further, these studies have not considered other dietary factors that might mask a beneficial fibre effect such as total caloric intake or dietary fat.
“Fibre has been shown to have a protective effect, but microbiota and butyrate presence does determine the degree of protection,” explained Bultman. “We have discovered that butyrate accumulates in the tumour, where it functions as an inhibitor to epigenetically regulate genes involved in cell proliferation and apoptosis.”
Bultman is due to speak at Probiota 2016 in Amsterdam, where he will be discussing his research findings that reveal the potential – and constraints – of fibre for tumour suppression. His work investigates how fibre, the microbiota and butyrate interact to reduce colorectal tumours in mice. He will also discuss the impact these factors have on future cancer treatment and prevention.
Changing lifestyle
He told NutraIngredients: “As human populations shift away from traditional, high-fibre diets towards processed foods containing refined sugars; colorectal cancer incidence has increased markedly. This trend of increasing colorectal cancer incidence is most evident in China and developing countries that have rapidly adopted western diets in recent years.”
“This increase means our research has even more implications for future human health and cancer treatments. Aside from the benefits of a high-fibre diet, our findings may also deliver new insights into the role bile acids in meat and in particular, the effect deoxycholic acid has on cancer proliferation. Likewise, the cancer protective effects of polyphenols and plants are already well-known.”
Despite the conflicting studies, Bultman said dietary fibre has a protective effect. “I’m excited by our work because it combines the three main factors that influence cancer pre-disposition - diet, microbiota and an abundant metabolite,” he said.
Study trends
“The current trend is to move beyond basic microbiome studies, and evaluate the effect of diet and other environmental factors on microbial abundance (metagenomics) plus microbial gene expression (metatranscriptomics and metaproteomics) and metabolite production (metabolomics).
“What we’d like to do in the future is to track a large sample size and enrol them onto an epidemiological and microbiome study. Here, we would be better able to distinguish between the responders and non-responders further investigating those that respond more favourably.”
It will become increasingly important that scientists are able to culture specific bacteria so they can be analysed in gnotobiotic mouse models. This approach will allow a move from correlation to causation and will provide insight into molecular mechanisms, which may lead to improved probiotic/prebiotic strategies of disease prevention.
Bultman will be presenting his talk: 'An end to controversy? The fibre-microbiota-butyrate axis in tumour suppression' on day 2 of the event (February 3).
Pre- and probiotics will be discussed at Probiota 2016 in Amsterdam on February 2-4.
From zombie probiotics to the future of microbiome science; global hotspot market wraps; infants and the aged; case studies; latest research and formulations plus regulations Probiota 2016 is a knowledge store you probably shouldn’t miss.
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