12 April 2016 - Nutraingredients - Mind the fibre gap: The case of the vanishing gut microbiome

Increasing dietary fibre intake may be the best way to regain the microbial biodiversity that has been impaired by the western diet, according to researchers.

In a commentary piece, the authors point to an insufficient nutrient intake as causing the loss of beneficial gut bacteria. This observation is most evident in industrialised societies.

One key nutrient that is lacking in the western diet is fibre. A typical westerner consumes half the fibre recommended in some dietary guidelines.

This 'fibre gap' presents a problem since dietary fibre is the primary source of nutrition accessible to gut bacteria in humans.

According to the researchers, this is leading to not only the loss of species reliant on this energy source but also a reduction of fermentation end-products that key physiological and immunological functions rely upon.

“By shifting to a diet that is fundamentally different to the diet under which the human–microbiome interrelationship evolved, we might have disrupted this symbiosis, reducing or removing the evolutionary routed benefits provided by the microbes,” said Jens Walter of the University of Alberta, Canada and co-author of the study.

“This process might have contributed to the rise of NCDs and a substantial degree of morbidity and mortality providing a strong incentive to consider attempts to conserve and potentially restore the gut microbiome.”

Low-fibre implications

Boosting fibre levels for health reasons is not a new idea. However, damage to microbiome diversity adds another reason as to how a low-fibre western diet is affecting the wellbeing of an individual and population.

The loss of microbial biodiversity in different populations has been observed in a number of studies using animal and human subjects.

Gut microbiome composition of those living in industrialised societies results in an individualised response to dietary fibre that may increase variation in findings from human trials.

One study that asked African American subjects to stick to a traditional South African diet with a daily dose of 55 g of dietary fibre showed improved markers of colon cancer within two weeks.

Closing remarks

Walter and co-author Edward Deehan concluded by discussing what scientists, food producers, policy makers and regulatory groups could do to address this fibre gap.

They emphasised that clinical assessments of different fibre types and fibre-enriched foods on microbiome outcomes were needed.

However they warned that the additional costs associated with high-fibre diets would still likely prevent them from being broadly embraced, as indicated by the inverse relationship between socioeconomic status and dietary fibre intake.