Beware the ‘fibre-gap’!
Scientists from the University of Alberta, Canada have recently published an article summarising that the lack of fibre in a typical Western diet is playing havoc with our microbiome. UK government guidelines stipulate that adults should be consuming at least 30g of fibre each day, but records suggest that on average we are only consuming 18g per day. The short-fall between the recommended daily amount, and our average daily intake, is being referred to as the ‘fibre gap’.
Dietary fibre (in its different guises) is the primary source of nutrition for our gut bacteria. Without sufficient fibre, species of bacteria that rely solely on prebiotics (which are a type of fibre/resistant starch) for their fuel source, struggle to survive. Not only does this lead to the loss of certain species of good bacteria from the intestinal flora, but it also leads to a reduction in their fermentation end-products such as short-chain-fatty-acids (SCFAs), which have many key functions in the body. The Canadian research looked at many different clinical studies, and concluded that low fibre diets are negatively impacting on microbial diversity in the intestines, and this reduction in ‘friendly’ bacteria is linked to lowered immunity and therefore an increase in chronic ‘non-communicable diseases’ (NCDs) such as allergies, obesity, cardiovascular disease, autism, autoimmune conditions and even colon cancer.
Jens Walter was one of the co-authors of the article, reviewing the impact of a low fibre diet on gut bacterial diversity. In the article he refers to a study (1) in which African American study participants were asked to follow a traditional South African diet, containing 55g of fibre per day. The results of the study showed that after as little as two weeks on the diet, colon cancer markers were significantly improved.
In conclusion the authors state that whilst increasing dietary fibre through the use of fibre-enriched flours and cereals or through the use of fibre supplements, can help to feed and therefore bolster ‘dwindling’ probiotic colonies, it can not be presumed that it will reinstate ‘lost’ colonies. Any strains that have disappeared from the microbiome completely would need to be reintroduced through the use of probiotic supplements or fermented foods (dependent on the strains required).
Reverting back to a higher fibre diet, more similar to those that our ancestors enjoyed, could offer protective effects to our gut bacteria by providing them with a constant source of nutrition. In return for our efforts our gut microbes would 'repay' us highly, by producing health-promoting SCFAs and other beneficial micronutrients, which have physiological and immunological effects . A win:win situation for both us and our gut bacteria you could say!
- Fat, fibre and cancer risk in African Americans and rural Africans.O’Keefe, S.J.D. et al.Nat. Commun. 2015; 6: 6342