I spent Thursday afternoon at at St Thomas’ Hospital, attending #BNFNewFibre, a British Nutrition Foundation half day seminar on dietary fibre research. In four short hours we heard from eight nutrition academics and researchers studying new uses for fibre.
The European Food Safety Authority (EFSA) has deemed specific forms of fibre may be recommended for maintaining cholesterol levels, maintaining normal bowel function, reducing post-prandial glycemic levels, increasing fecal bulk and reducing intestinal transit time.
It is the term “fibre” that is problematic, though: soluble vs insoluble; dietary vs functional; whole food sources vs manufactured, extracted and refined, and so on. Since many health claims do not specify the precise type of fibre they are talking about, it is difficult to make sweeping conclusions about intake and effect.
And of course, we are each biochemically unique, the health of our microbiome affected by many factors (age, genetics, pregnancy, lactation, environment, dietary habits, medical conditions and interventions, antibiotic use, etc) not all of which we can control or even identify. These same factors determine our need for fibre, which feeds the hundreds of different strains of beneficial bacteria throughout the length of our digestive system.
We have only identified some 200 unique strains, and 600,000 unique microbial genes, so we have barely begun to learn the position and role these play within our metabolism.
We don’t yet have a good understanding of how fibre works in the microbiome to protect against cardiovascular disease or increase calcium uptake (to protect against osteoporosis), or how it may interact with bile acids, in gene expression or in immune support. Research suggests it may increase satiety, leading to weight loss or protecting against obesity.
Fibre is often included in health advice (either avoiding or adding to the diet) for treatment or prevention of a whole array of medical conditions (colorectal cancers, enteral feeding, irritable bowel disease, irritable bowel syndrome, diverticulitis, radiation toxicity, constipation..)
The speakers whirled through dozens of studies in these areas – published and in process – and left us with the unsurprising conclusion that fibre studies are maddeningly difficult to do with accuracy and consistency (humans being maddeningly diverse in their habits and behaviour, subjects being less than numerous in many studies due most likely to the expense of dietary research, and the very nature of fibre which differs greatly in its chemical composition and effects in the body). And that much more needs to be known.
All this was discussed in the context of last year’s daunting Scientific Advisory Committee on Nutrition (SACN) recommendations which propose raising the already unattained 18g recommended daily fibre consumption to 30g/day for British adults (in Canada it’s 38g for men under 50 or 25 for women).