Fiber medicine

Researchers say individualized fiber recommendations may soon be possible

The new research was conducted by researchers from the Department of Gastroenterology at Monash University in Melbourne, Australia. The research was published in the journal Intestinewho is one of British medical journalpublications.

The researchers noted that the amount of data available on different fibers has exploded in recent years. Decades ago, it was known that increased fiber intake was beneficial for avoiding unpleasant gastrointestinal symptoms, but little was understood beyond that.

How has fiber been beneficial? Was it just a mechanical effect, the old idea of ​​”fodder”? Did undigested fibers absorb toxins for better excretion of them, thus reducing inflammation? Was the fiber fermented and gave rise to more beneficial microbes and the metabolites they secrete? If so, did it matter where in the intestine this fermentation took place?

Fiber categorization

Dietary fibers can be classified into several categories. One of the most basic is the difference between whole fiber as presented in the food matrix itself and isolated or purified fiber. This first was born from the separation of various cereal grains from their husks giving rise to the ingredients of wheat bran, rice bran and corn bran.

Later, ingredient developers began isolating fiber constituents from these raw materials. This has allowed for more accurate characterization of the health benefits of these ingredients as well as formulation flexibility in a variety of prepared foods and supplements such as meal replacements and nutrition bars.

Fibers can be classified by the type of monosaccharides from when they are constructed and the number of molecules they contain, called the degree of polymerization (DP). Thus, there are fructo-, xylo- and galactooliogosaccharides (DP 3–9) and polysaccharides (DP ≥10). Polysaccharides include non-starch varieties that cannot be digested and resistant starches (RS).

In recent decades, fiber has also been categorized into “soluble” and “insoluble” varieties. Although the way these fibers are delineated on food labels in the United States may imply important functional differences in the gut, the researchers said this has more to do with how the fibers are isolated from their source material and analyzed.

Finally, there are differences between these fibers in the complexity of their molecular structures, which have profound functional implications. For example, non-viscous cellulose is made up of individual units tightly bound together, while psyllium fiber is bound is a loose structure. This makes it much easier for fermenting bacteria to access sites on the psyllium molecule to break it down.

Importance of the Triad of Fiber Effects

The first concept of “roughage” fiber was not wrong, just incomplete. Australian researchers said fiber has a bulking function, in which fiber molecules help retain water in the stool and increase stool weight. But fiber is also important for maintaining the healthiest stool viscosity. And fiber fermentability has been shown over the past few decades to have a multitude of beneficial microbiome-modulating functions.

Putting it all together, the researchers said fibers can be placed along a three-axis graph measuring viscosity, swelling potential and fermentation rate. Most of the commercially important isolated fibers such as fructans (inulin is an example), GOS, FOS and partially hydrolyzed guar gum (PHGG) fall in the part of the graph where they all have low viscosity and low swelling properties, but range from moderate to moderate. fast in terms of fermentation rate.

Towards an individualized approach

Just as all of these different fibers have different properties, irritable bowel syndrome (IBS) also presents differently in different people. If the unifying theme is that of moderate to severe intestinal inflammation, this inflammation can be more important in different places of the digestive tract. And this can be accompanied by varying degrees of symptoms such as pain, severe constipation, chronic diarrhea and cases of severe bloating.

So while the recommendation to eat more fiber is commonly given to consumers to maintain digestive health, for IBS patients the picture is more nuanced.

The researchers said the field of fiber research is approaching the point where individualized fiber therapies might be possible.

“Despite the functional characteristics of dietary fiber, there has been much confusion about its value for IBS patients, partly because of its overly simplistic classification, partly because of the general lack of consideration of heterogeneity in patients and partly limitations of RCTs conducted to date.By embracing different fiber types as specific compounds with distinct functional characteristics, we have described how distinct physiological responses induced by specific fibers can potentially be exploited by their judicious application under appropriate physiological conditions with possible improved clinical results”,concluded the researchers.

More data needed to complete a complicated matrix

However, it becomes a complicated game of matching specific fiber properties with outcome goals, such as normalizing bowel habits, beneficial changes in the gut microbiome, or finding a way to deliver fiber in concert. with dietary strategies like the FODMAP diet, in which too low a fiber intake is a risk.

“It is clear that applying fiber heterogeneity and its effects to a physiologically heterogeneous IBS population is challenging, and it is not surprising that therapeutic studies with the unique approach have had poor results. Individual patient characteristics may need to be included in fiber therapy choices,” wrote the researchers.

“[W]Well-designed dietary trials conducted to assess the clinical value of fiber types using endpoints aligned with their functional characteristics are needed. Future work aimed at establishing physiological measures to predict the likelihood that patients will respond effectively to fiber therapies will greatly improve the ability to personalize the selection of the optimal fiber(s),”they added.

GPA: Researcher findings match industry outlook

Len Monheit, executive director of the Global Prebiotic Association, an industry trade group, welcomed the new research and the authors’ recommendations.

“The Global Prebiotic Association supports the hypothesis that a one-size-fits-all approach to using fiber as a management strategy for IBS is not ideal,“, said Monheit.

At the top, there is the phenomenon of responders vs non-responders. It has also been established that fiber may be a trigger for IBS in certain populations of people with IBS, suggesting a diagnostic and personalization component if this should be an established or considered treatment. We suggest the terms digestible versus indigestible because the breakdowns of fiber types are inadequate and not specific enough to really advance science and care in this area,” he added.

As the authors point out and as supported by emerging science, there may be a number of therapeutic outcomes modulated by different types of prebiotic fibers/carriers that may differentially impact short chain fatty acid synthesis and also trigger fermentation at different stages of the intestine”,concluded Monheit.

DO I: 10.1136/gutjnl-2021-324891
Dietary Fiber and IBS: Translating Functional Traits into Clinical Value in the Age of Personalized Medicine
Authors: So D, et al.