Is a High-Fibre Diet Good for the Microbiome?

Is a high-fibre diet good for the microbiome?

Check out this answer from Consensus:

The evidence strongly supports the notion that a high-fiber diet is beneficial for the gut microbiome. It promotes the growth of beneficial bacteria, increases the production of health-promoting SCFAs, reduces inflammation, and improves metabolic health. These findings underscore the importance of incorporating a variety of dietary fibers into our daily diet to support gut health and overall well-being.

The human gut microbiome plays a crucial role in maintaining overall health, influencing various physiological processes including digestion, immunity, and even mental health. Recent research has increasingly focused on the impact of diet, particularly dietary fiber, on the composition and function of the gut microbiota. This article explores whether a high-fiber diet is beneficial for the microbiome, drawing on findings from multiple studies.

The Role of Dietary Fiber in Gut Health

Dietary fiber is a type of carbohydrate that the human body cannot digest. Instead, it serves as a food source for gut bacteria, promoting their growth and activity. Different types of dietary fiber, such as fructans, galacto-oligosaccharides, and intact cereal fibers, have been shown to influence the gut microbiota in various ways.

Effects on Microbiota Composition

Several studies have demonstrated that a high-fiber diet can significantly alter the composition of the gut microbiota. For instance, a systematic review and meta-analysis found that dietary fiber interventions increased the abundance of beneficial bacteria such as Bifidobacterium and Lactobacillus spp. in healthy adults2. Another study highlighted that intact cereal fibers, including wheat bran, led to increased microbiota diversity and abundance, with effects observable from as little as 24 hours to up to 52 weeks3.

Short-Chain Fatty Acids (SCFAs) Production

One of the key benefits of a high-fiber diet is the production of short-chain fatty acids (SCFAs) through the fermentation of fiber by gut bacteria. SCFAs, such as acetate, butyrate, and propionate, play a vital role in maintaining gut health and have been linked to various health benefits, including reduced inflammation and improved metabolic health. A study on hypertensive mice showed that a high-fiber diet increased the abundance of acetate-producing bacteria, which in turn helped prevent the development of hypertension and heart failure4.

Impact on Inflammatory Markers and Metabolic Health

High-fiber diets have also been associated with reduced levels of inflammatory markers and improved metabolic health. For example, a systematic review and meta-analysis on patients with type 2 diabetes found that dietary fiber significantly increased the relative abundance of Bifidobacterium and decreased levels of lipopolysaccharides (LPS), total cholesterol, and body mass index (BMI)1. Another study demonstrated that fermentable fiber, such as inulin, protected against diet-induced obesity and metabolic syndrome by restoring gut microbiota and promoting the production of interleukin-22 (IL-22), which is crucial for maintaining gut barrier function9.

Microbiota Stability and Richness

The stability and richness of the gut microbiota are important for maintaining a healthy gut environment. A study found that higher microbiota richness was associated with greater stability upon increased dietary fiber intake, suggesting that individuals with a more diverse microbiota may benefit more from dietary fiber interventions6. This stability is crucial for long-term gut health and resilience against dietary changes.

 

 

Is a high-fibre diet good for the microbiome?

Eric C Martens has answered Near Certain

An expert from University of Michigan Medical School in Microbiology

Fiber is very likely to positively impact the microbiome! Our own digestive functions, which mostly occur in the small intestine, are effective at breaking down and/or assimilating the simple sugar (glucose, fructose, sucrose) and starch carbohydrates in our diet, along with fats and protein. However, digestion of fiber, which is mostly complex polysaccharides (sugar chains) found in fruits, vegetables, whole grains and nuts requires specialized enzymes that are absent in humans and therefore not present in our small intestine. Its important to distinguish these two major classes of “carbohydrates” that exist in our diet, since the first class (sugars and most starch) is a more direct source of energy and extra calories that in excess can be bad; whereas, fiber carbohydrates provide fewer calories, may make us feel more full and also directly impact the gut microbiome.

Our gut microbiome lives downstream of where we digest sugars, starch, fat and protein, mostly in the large intestine (colon) and has evolved in large part to feed off of the fiber that we cannot digest on our own. As such, the amount of fiber in our diet impacts the metabolism and species composition of this microbial community. In the oxygen-free environment that exists in the large intestine, members of the microbiome ferment fiber into molecules called short-chained fatty acids that can be absorbed by our intestinal cells and positively impact several aspects of our health, including immune system development and blocking growth of cancer cells.

There is also an enormous amount of chemical variation present in different fiber polysaccharides! These nutrients can be short or long, composed of different sugar building blocks and even vary in subtle but important ways between different foods (e.g., tomatoes vs. lettuce or wheat vs. corn). An important scientific question that is still being worked out is how these different variations impact various microbial members of the microbiome, some of which have been implicated in preventing or accelerating diseases like inflammatory bowel disease or colon cancer, and a number of other conditions, like allergies, that occur outside of the intestine. Until science figures out the details of how to use specific fiber containing foods to more precisely impact the gut microbiome, daily consumption of 25-50g of fiber from a diverse and colorful assortment of vegetables, beans, grains, nuts and fruit is very likely to be a good dietary habit that will both benefit your gut microbiome and increase your overall nutrition and health in other ways.

 

Is a high-fibre diet good for the microbiome?

Arthur C Ouwehand has answered Near Certain

An expert from DuPont Nutrition and Health in Microbiology

Most dietary fibres are one way or another fermentable and provide an energy source for the intestinal microbiota. This is a preferred source of energy for the microbiota. In it’s absence, and that may happen in particular in the distal part of the colon when most fibre has already been utillised, the microbiota will turn to the fermentation of proteinacious components which will lead to the formation of potentially detrimental metabolites. Fibre on the other hand leads to the formation of beneficial metabolites such as acetic, propionic and butyric acid. These so-called short chain fatty acids may also lower the pH of the colonic content, which may contribute to an increased absorption of certain minerals such as calcium and magnesium from the colon. The fibre fermenting members of the colonic microbiota are in general considerd beneficial while the protein fermenting members are considered potentially detrimental.

 

Is a high-fibre diet good for the microbiome?

Jens Walter has answered Near Certain

An expert from University of Alberta in Microbiology, Evolutionary Biology, Ecology

The mutualistic relationship that humans maintain with their gut microbiome has evolved over million of years in a dietary environment that provided more than a hundred gram of dietary fiber per day. So our gastrointestinal physiology, and even our immune system and metabolism, are adapted to a high provision of dietary fiber. The benefits that have been established are too numerous to list here exhaustively, but dietary fiber is fermented to short-chain fatty acids (SCFAs) with beneficial metabolic, physiological, immuno-regulatory, and anti-cancer effects. SCFA improve intestinal barrier integrity and reduce local and systemic inflammation, inhibit bacterial pathogens, and induce beneficial epigenetic events in colonic cells. By providing a growth substrate for microbes, dietary fiber might be able to maintain microbiome diversity, and it shifts the metabolic focus of the microbiome away from the degradation of the mucus layer and the fermentation of protein to detrimental compounds. These are some of the mechanisms by which scientists think fiber exerts its health benefits, which range from the prevention of obesity, heart disease, type-2 diabetes, and colon cancer. Dietary fiber is therefore almost certain to be good for the microbiome, and in consequence, for its host. It is therefore unfortunate that dietary fiber consumption is much too low on average in industrialized societies (and much lower to that of our ancestors), and a diet high in fruits, vegetables, whole grains, and nuts is encouraged by dietary guidelines.

 

Is a high-fibre diet good for the microbiome?

Volker Mai has answered Near Certain

An expert from University of Florida in Epidemiology, Microbiology

Yes, it is good for the microbiome as it provides nutrients that reach the large intestine, where they can be fermented by gut microbes that possess the required enzymes to digest fibre. However, it is less clear that this benefit to the microbiome is also beneficial to the Human host. While there are established benefits of high fibre intake on various health benefits, it is unclear that changes in microbiome composition and/or activities contribute significantly to any of the established health benefits.

 

Is a high-fibre diet good for the microbiome?

Hermie J M Harmsen has answered Likely

An expert from University Medical Center Groningen in Microbiology

Fibre rich diet is very important for us. High-fibre suggests it is particularly high in fibre, this may be extreme and depends on the circumstances. Fibres are degraded by bacteria that are mostly associated with a healthy gut, such as Prevotella, Ruminococci, Bifidobacteria, Lachnospiraceae and Faecalibacteria. Working together, they produce short chain fatty acids, such as acetate, propionate and butyrate, of which the latter is most determinant for gut health, since it stimulated the epithelial barrier function and the immune system. 

Fibres also benefit water homeostasis in the gut, and stimulate bowel movement, given pleasantly soft stools.

However too much is never good, and it always should be a balanced diet for a balanced microbiome.

 

Is a high-fibre diet good for the microbiome?

Gunnar C Hansson has answered Near Certain

An expert from University of Gothenburg in Gastroenterology

Our commensal bacteria are experts n degrading complex saccharides often called fibers and the mucins produced by host cells. These baceria shall in the normal case be separated from the epithelium by the inner mucus layer that acts as a filter excluding bacteria due to their size. It is clear that these bacteria secrete both energy in the form of acetate and proprionate, but also more specific metabolites that can stimulate the formation of a functional inner mucus layer. Depending on the bacteria, their genetic setup, and the available fibers and other nutritional sources they will synthesize different metabolites. There are an enormous variability in structure of fibers, in bacterial types and espcially in the genetic setup of bacteria, together suggesting that all these pieces have to collaborate to have beneficial or maybe even detrimental effects on us.

See also Schroeder et all Cell Host&Microbe (2018) 23. 27-40 and Jacobsson et al EMBO Reports (2015) 16, 164-177.

 

Is a high-fibre diet good for the microbiome?

J Lu has answered Extremely Unlikely

An expert from Institute of Disease Control and Prevention, China in Microbiology

The long-term High-fibre supplementation would inhibit the growth of some kinds of microbiota, likely causing deregulation of body metabolism.

 

Is a high-fibre diet good for the microbiome?

Joël Doré has answered Near Certain

An expert from Institut National de la Recherche Agronomique in Microbiology, Ecology, Genomics

To complement other comments suggesting that dietary fibers will almost certainly be good for the microbiome, I will add that intestinal microbes interact in a food chain of which primary degraders are microbes adapted to obtain energy from the degradation of complex structures such as polysaccharides. Primary degraders thereafter feed fermentative microbes with oligosaccharides and intermediate products until final utilizers and producers of fermentation gases such as methanogens complete this ecological landscape.

Of the food we ingest only a small fraction will be food for our microbes and its essentially fibers which, by definition, are not degraded by human digestive enzymes, and hence will reach the distal segments of the intestine where the microbiota is most dense and diverse. Yet microbes that have adapted to fiber degradation for millennia do not see “lettuce, carrots or apples”; they see molecular structures such as cellulose, hemicellulose, xylans, pectins… inasmuch as they have acquired a specialized enzymatic equipment that allows them to benefit from their breakdown. Cellulose degradation requires more than 20 genes in spite of its very simple structure (beta-1,4 bound glucose). Each fiber molecular structures will hence be degraded by a limited set of highly specialized microbes. This means that providing a diversity of fibers will open a diversity of ecological niches and thereby promote a diversification of the dominant microbiota. In turn this will promote a diversification of the overall microbiota ; a feature that is recognized across many studies as beneficial, noticeably associated with protection of gut barrier integrity and immune homeostasis.

 

Is a high-fibre diet good for the microbiome?

Denis Roy has answered Likely

An expert from Université Laval in Microbiology

The intestinal microbiome has co-evolved with the human host to perform a number of physiological, nutritional and immunological functions, including helping to degrade food particles and producing short-chain fatty acids (SCFA). Among bacterial groups present in the large intestine, and known to play a role in the well-being and health of the host, bifidobacteria occupy a prominent place. Bifidobacteria can produce acetate by degradation of fibers and prebiotics that become available to butyrate-producing bacteria. The analysis of the genomes of  Bifidobacterium species reveals a strong selective pressure to the acquisition and retention of accessory genes necessary for the degradation and internalization of a wide range of carbohydrates. Bifidobacteria are metabolically active in the lower part of the colon using trophic interactions, which may vary from commensal to mutualistic. They have also access to a wide variety of polysaccharides and oligosaccharides of plant origin that are not digested by the host, as well as host glycans such as mucin and HMO. Their functional contribution to the human gut microbiome through cross-feeding activities can be important in terms of expanding the global glycobiome of the large intestine and affecting the overall physiology of the host intestine.

 

Is a high-fibre diet good for the microbiome?

Alyssa M Burns has answered Near Certain

An expert from University of Florida in Nutrition

It is important that we consume fiber rich diet. Dietary and functional fibers may stimulate the growth of potentially beneficial bacteria associated with health and overall all well-being, such as Lactobacilli and Bifidobacteria. These bactereria may also promote the integerity of the intestinal barrier and add diversity to the microbiome. Prebiotic fiber fermentation by the microbiota lead to the production of short-chain fatty acids, that are used as energy source for colonic cells or even involved with immune function. Adequate fiber intake may also promote laxation, fecal bulking and may decrease the risk of developing various chronic diseases. A fiber rich diet may also benefit those experiencing diarrhea or constipation. Depending on the condition consuming an adequate fiber diet may decrease unwanted symptoms.

It is recommended to consume a diet rich in a variety fiber sources. Fiber has many unique properities including solubility, fermentablity and viscosity that contribute in differnt ways to our overall bowel health and microbiome.

 

Is a high-fibre diet good for the microbiome?

Anthony R Bird has answered Near Certain

An expert from Commonwealth Scientific and Industrial Research Organisation in Microbiology, Nutrition, Physiology

Eating a diet rich in fermentable fibre increases numbers and activities of gut bacteria associated with better health outcomes.

Fibre fermentation produces short chain fatty acids, and these bacterial metabolites help create a (mildly acidic) colonic luminal environment favourable to the growth of beneficial microbes while discouraging proliferation of potentially harmful ones. Short chain fatty acids are vital for normal bowel function and health but they also have beneficial effects beyond the gut as well.

Regardless of the mechanism, eating a plant-based diet rich in a variety of different dietary fibres delivers many health benefits, including reduced  risk of common non-communicable diseases.

 

Is a high-fibre diet good for the microbiome?

Barbara A Williams has answered Near Certain

An expert from University of Queensland in Animal Production

Not all dietary fibre is the same. It is actually a collective name given to the group of compounds originating from plant foods- the plant cell walls. If you think about the variation found in plant foods (fruit, vegetables, cereal grains, and legumes), then the variation in dietary fibre is almost as great. The most important question is- is the fibre fermentable? In other words, can it be used as a source of energy by the huge (and highly diverse) bacterial population living in the gut? If these bacteria have a ready source of energy in the form of dietary fibres, the population will be more stable, and diverse, and maintain their diversity, all elements which are considered to be signs of a healthy microbiota (the actual bacteria population). On the other hand, if there is insufficient energy as fibre, the bacteria will switch over to fermenting whatever is available to them, and this can often lead the to production of chronically toxic compounds (such as ammonia). So overall, a diet high in a wide variety of fibres will result in the best outcome in terms of the gut microbiota and overall health. However, the diet is a case of “balance and moderation”. It would also be inappropriate to have a diet of “only” dietary fibre.

See also: Lozupone et al (2012) Nature 489:220-230; and Flint et al (2012) Nature Reviews Gastroenterology & Hepatology 9:577-589