Fibre Optics
For many years now, the world of popular nutrition has not paid enough attention to fibre. Although the consumption of it has long been regarded as important to health, this has largely been due to its role in ‘keeping us regular’, helping with such un-glamorous benefits as faecal bulking and intestinal transit. Fibre based diets such as the F-Plan or Rosemary Conely seem to be of a different era, dietary museum pieces with little appeal, even to the most health conscious of modern consumers.
More recently, fibre has at least been half-lauded as having a role in the health of our microbiome, that most ubiquitous of modern health fads. But even in the most devoted areas of microbiome-land, fibre tends to (wrongly) play second fiddle to the various flashy probiotics and fermented health panaceas that constitute the largest revenue streams for the increasingly valuable gut health industry.
Away from fads and fashions however, in the world of serious nutrition research, fibre is increasingly being recognised as perhaps the most complex and nuanced of the major nutrients. It is certainly still considered vital for maintaining good health, but at the same time it is proving to be frequently underestimated, misunderstood and hard to classify. Even well-established methods for measuring the amount of fibre in food stuffs are proving to be both inadequate and inaccurate, and the mechanisms that underlie the enormous potential health benefits are, in many cases, only just being fully uncovered. In this series of articles, an emerging picture of modern fibre-science will be explored, to try and understand how it might benefit consumers and be used to improve population health.
Fibre is Different
Measuring and defining most of the macronutrients in our food, such as proteins, fats or carbohydrates, is relatively straightforward. If we can get a good idea of the size, molecular composition, and basic structure of these nutrients, and combine that with information about how much we consume, we can make some basic predictions about how they will act in our bodies. Most of these substances are broken down in our mouths, stomachs and small intestines into chemical components small enough to be absorbed into the bloodstream, where they are either metabolised into energy, or converted into the various chemical building blocks required to make our bodies.
Fibre, by definition, works differently (although as we shall learn, defining fibre is half the problem). A simple (probably over-simple) definition of fibre is any component of food that is not absorbed in the upper reaches of our digestive tract and so reaches our large intestines intact. Once there, it either passes straight through our bodies undigested, or becomes food for the many hungry microorganisms that comprise the gut microbiome, which in return for their fibre-y meal, produce a host of valuable micronutrients and anti-inflammatory substances. Perhaps even better, a healthy, well-fed microbiome is known to protect against infection from nefarious microorganisms, leading to confident boasts that fibre can help fight disease, a significant claim in a world rocked by a recent pandemic. The fact that there is precisely zero evidence that fibre or the microbiome can help prevent infection by the SARS-CoV-2 virus that causes Covid19, which to my knowledge has never been absorbed through the large intestine, is perhaps not as talked about as often as it should be.
I am certainly not about to downplay the health benefits of fibre, or indeed the vital role of the microbiome in maintaining good health. Quite the opposite in fact, those things are extremely important and much of my professional and writing work has been dedicated to finding ways of persuading people to eat more. But if we think of fibre as simple microbiome food and assume that this is the sole reason for its health benefits, then not only are we doing it a disservice, we are in danger of making the wrong decisions about how we incorporate it into food.
Fibre Contains Multitudes
There are many different types of fibre with widely varying forms and functions in the body. Even within those different types, variations in molecular size and structure can play an important role that we are only just beginning to understand. And at the larger scale, how fibre is incorporated into macro-structures such as the intact cell walls found in many plant foods, can massively alter how it impacts our bodies.
It also increasingly seems that the way fibre is processed by the food industry is far more important than was previously realised. For instance, the fibre contained in whole cell pulse flours is a very different beast to that found in heavily milled wheat brans, and these are a world away from gel forming beta-glucans, soluble inulin, pectin, waxes, or lignin.
None of this complexity is reflected in the amount of fibre listed on food labels, and rarely are the different types of fibre considered in dietary surveys or nutrition recommendations. Studies of the impact of fibre on health usually take a broad-brush approach, classifying it as one entity with a single unified impact on the body, whereas the reality could not be further from the truth. Even the way that scientists and food manufacturers measure the amount of fibre in food appears to be providing an inaccurate and inconsistent picture.
‘So what?’, you might ask. Nutrition labelling is already too complex for consumers to understand. Adding the average molecular weight of beta-glucans, or the percentage of intact cellular structures into the labelling mix is hardly likely to make things clearer.
In reality, this emerging area of nutrition science is probably not destined to become a strongly consumer facing proposition. But the complexity of fibre should be something that the food industry strives to understand so we can use this new knowledge to create healthier products and better methods of processing. With an increasingly large proportion of population calories coming from processed foods, and an even larger percentage of our total fibre coming from such sources, food manufacturers often represent the gateway to this vital nutrient. But for consumers to really benefit, we need to improve both the quality and the quantity they are being providing with.
Goodhart’s law states that as soon as a measure becomes a target, it ceases to be a useful measure. This could easily be said of fibre, where nutritional targets often lead to food being arbitrarily fortified with the simplest, cheapest or most palatable forms. As we shall learn, these might not always be the ‘best’ forms for a particular health benefit or outcome, although equally, they might not always be the worst. The true picture is one that is still at the edge of our scientific understanding and is likely to be difficult to communicate clearly to consumers.
If the industry is serious about improving the healthfulness of manufactured foods, it will probably have to look more holistically at how products are produced, and particularly at how we treat fibre. The hardest part of this journey will not be understanding the science or incorporating new ingredients. It will be getting away from our obsession with targets and allowable health claims and just striving to make better food.
