Dietary Fibre: Is It Really Essential?

Is fibre something the human body needs, or has its importance been overstated?

Dietary fibre is often presented as an essential part of a healthy diet. We are regularly advised to eat more vegetables, fruit, whole grains, beans, nuts and seeds to make sure we get enough. Official guidelines recommend daily amounts, and fibre is often linked to better digestion and protection against certain diseases.

But there is an important question that deserves closer attention: does the human body actually need dietary fibre?

Something can have an effect on the body without being essential. So, does everyone need to eat fibre to stay healthy and maintain normal digestion? And how did fibre become such an important part of the advice we receive about food?

To answer these questions, we look at the history of fibre promotion, the commercial interests behind some of its marketing, and what scientific research has actually found.

1. What Is Dietary Fibre?

Dietary fibre is found in plant foods such as vegetables, fruit, grains, beans, nuts and seeds.

Unlike sugars and starches, fibre is not broken down and absorbed in the small intestine in the same way as other carbohydrates. Much of it passes further through the digestive system.

Not all fibre behaves in the same way.

Some types absorb water and form a thick, gel-like substance. Others add bulk to the contents of the intestines. Some are broken down by bacteria in the large intestine through a process called fermentation.

Because different types of fibre behave differently, they can also have different effects on digestion.

But the fact that fibre passes through the digestive system and can influence digestion raises an important question: does the body actually need us to consume it?

2. Is Dietary Fibre an Essential Nutrient?

An essential nutrient is something the body needs but cannot make enough of on its own. We must therefore obtain it from the food we eat.

Examples include certain vitamins, minerals, amino acids and fatty acids.

Dietary fibre is not classified as an essential nutrient.

The National Academies of Sciences, Engineering, and Medicine identifies dietary fibre as a non-essential food component. This means that fibre is not recognised as something the body must obtain from food to meet an established essential nutrient requirement. [1]

This does not mean that fibre has no effect on the body. A substance can influence digestion or other processes without being essential.

It is also important to distinguish between a recommended daily amount and an essential requirement. Recommendations can be based on particular health outcomes. They do not automatically prove that the body must consume a substance to function.

The important question is therefore not simply whether fibre has an effect, but whether those effects show that everyone needs to eat it.

3. How Did Dietary Fibre Become a Health Priority?

Dietary fibre became a major part of public dietary advice through a combination of scientific interest, health claims and commercial promotion.

The history of bran and bowel regularity

Kellogg promoted bran cereals as products intended to prevent constipation and encourage regular bowel movements. These claims became an important part of the company's advertising and helped establish bran cereals as products associated with digestive health.

Historical research shows that Kellogg was promoting bran for bowel health as far back as the early twentieth century. The advertising helped teach consumers to associate bran with regular digestion and helped the company build its position in the breakfast cereal market. [5]

However, advertising claims do not prove that a product reliably provides the health benefits being claimed.

Research into wheat bran has since produced a more complicated picture.

A 2025 review by the US Agency for Healthcare Research and Quality examined studies of fibre and bowel function. In its analysis of wheat bran, the researchers found that bran increased stool weight. However, the results for how often people passed stools were inconsistent. Some studies also found that bran could make stools harder. Importantly, none of the wheat-bran studies in this particular analysis measured whether bran prevented constipation. [11]

This does not prove that bran has no effect on constipation. Some smaller studies involving people with constipation have reported improvements, although the evidence is limited.

The American Gastroenterological Association and American College of Gastroenterology reviewed the available research on bran as a treatment for chronic constipation. They concluded that the evidence was too weak to be confident about its effects. The study they assessed was small, and the improvement in bowel movements was not statistically significant. [12]

A small trial published in 1995 involving 24 people with chronic constipation did find that bran improved bowel frequency and the speed at which waste moved through the intestines compared with a placebo. However, the severity of accompanying symptoms did not differ significantly between the two treatments. [13]

These findings show that increasing stool weight is not the same as reliably preventing or treating constipation.

Bran can affect bowel function, but the available evidence does not show that it works consistently for everyone or that everyone needs to eat it to maintain regular bowel movements.

The growing commercial interest in fibre

During the 1970s, scientific interest grew in the idea that fibre might protect against certain diseases. Researchers began investigating whether differences in fibre consumption could help explain differences in disease rates between populations.

The commercial potential of this growing interest became particularly clear during the 1980s.

In 1984, Kellogg began promoting its All-Bran cereal by linking a high-fibre diet with a possible reduction in cancer risk. The campaign was conducted in cooperation with the US National Cancer Institute. Other cereal manufacturers also began promoting high-fibre products and making health claims about them. [6]

A 1989 study by the US Federal Trade Commission examined the cereal market and found that health claims in advertising influenced what consumers bought. The promotion of health benefits helped increase interest in high-fibre breakfast cereals. [6]

This history matters because cereal manufacturers had a direct financial interest in encouraging people to associate fibre with better health. The more important fibre became in public dietary advice, the more valuable it became as a selling point for their products.

The public was increasingly encouraged to see fibre-rich breakfast cereals as a way to improve health, even while some of the proposed health benefits were still being investigated.

4. Did the Proposed Health Benefits Stand Up to Clinical Testing?

One of the major claims used to promote dietary fibre was that eating more fibre could help prevent colorectal cancer.

The original idea was partly based on observations that some populations had lower rates of certain bowel diseases than others. Researchers suggested that differences in diet, including fibre intake, might help explain this.

However, observations alone cannot prove that fibre was responsible for those differences.

Later clinical research did not confirm some of the major claims.

In 2000, a large study published in the New England Journal of Medicine examined whether a wheat-bran fibre supplement could prevent the return of colorectal adenomas. These are growths in the bowel that can sometimes develop into cancer.

The study included 1,429 people who received either a high-fibre or low-fibre wheat-bran supplement.

After following the participants, the researchers found no significant difference in the return of these growths. They concluded that the wheat-bran supplement did not protect against recurrent colorectal adenomas. [7]

The cereal supplements used in this study were supplied by Kellogg. This is worth noting when considering the commercial connections surrounding fibre research. However, the fact that a company supplied the study products does not, by itself, prove that it controlled the research or its conclusions. [7]

The findings show why health claims should be tested rather than accepted simply because they are widely repeated.

This study does not prove that every type of fibre has no effect on every health outcome. It does show that a proposed cancer-prevention benefit cannot simply be assumed.

5. Commercial Interests and Nutrition Research

The history of fibre promotion also raises a wider question: how much influence can the food industry have on nutrition research?

Food manufacturers have a financial reason to support research into ingredients used in their products. This does not automatically mean that the research is wrong, but it does make it important to examine who funded a study and whether there were any financial interests involved.

A review published in JAMA Internal Medicine in 2016 examined the relationship between food-industry funding and the conclusions of nutrition studies.

The researchers found that industry-sponsored studies were more likely to reach conclusions that favoured the companies funding them. However, the difference in their combined analysis was not statistically significant, and the authors explained that the available evidence was not sufficient to measure the full effect of industry funding on research results. [8]

This does not mean that all research into dietary fibre was funded by food manufacturers. Nor does it mean that every industry-funded study is unreliable.

It does show why funding sources and financial interests should be examined when assessing nutrition research.

The commercial history of breakfast cereal manufacturers is particularly relevant when considering how fibre became so strongly associated with health in the public mind.

6. What Happens to Fibre During Digestion?

Most dietary fibre is not broken down in the small intestine in the same way as sugars and starches. Instead, it continues into the large intestine.

Depending on the type, fibre may absorb water, add bulk to stools or be used by bacteria living in the large intestine.

Some of these bacteria break down certain types of fibre through fermentation. This process produces substances called short-chain fatty acids. Three examples are acetate, propionate and butyrate.

Researchers have studied these substances because they can affect the environment inside the intestines and interact with other processes in the body. [3]

However, the fact that bacteria can use fibre and produce these substances does not prove that people must eat fibre.

It shows that certain bacteria can use certain plant components. It does not establish that the human body has an essential requirement for those components.

There is an important difference between something being involved in a biological process and something being essential to the body's nutritional needs.

7. Does Fibre Improve Bowel Function?

One of the main reasons fibre is recommended is because of its effects on bowel movements.

Some types of fibre can increase the weight of stools, change their consistency and influence how often someone has a bowel movement. The effects depend on the type and amount of fibre consumed.

A 2025 review by the Agency for Healthcare Research and Quality examined 118 studies involving different types of fibre and people with normal bowel function.

The researchers found that increasing fibre intake could produce small to moderate improvements in several measures of bowel function. These included stool weight, stool consistency, how often people passed stools and how quickly waste moved through the intestines.

However, the results varied depending on the type of fibre and the amount consumed. The researchers also found that no individual study directly answered the overall question of how different levels of fibre intake affect bowel function across the population. [11]

The European Food Safety Authority considered research on bowel function when setting its recommended fibre intake. It concluded that 25 grams of fibre per day is adequate for normal bowel movements in adults. This recommendation relates to bowel function. It does not establish that fibre is an essential nutrient. [2]

A recommended amount based on a particular health outcome is not proof that everyone must consume that amount.

Nor does it mean that people who eat less will necessarily develop digestive problems.

People can also respond differently to different types of fibre.

8. Can Fibre Cause Digestive Problems?

Fibre is often discussed as though eating more of it can only improve digestion. However, not everyone responds to fibre in the same way.

Some people experience bloating, gas, stomach discomfort or changes in bowel habits after eating particular types or amounts of fibre.

The way fibre absorbs water, the way bacteria break it down and the amount consumed can all affect how it behaves in the digestive system. Research into fibre and gastrointestinal health also describes differences in how people respond to different types of fibre. [4]

Different people may react differently to the same foods.

For someone who experiences digestive discomfort after eating fibre-rich foods, simply increasing fibre intake may not be the right solution.

This does not mean that all fibre causes digestive problems. It means that fibre should not automatically be assumed to be beneficial or suitable for everyone.

The fact that a food contains fibre does not, by itself, prove that it is suitable for every individual.

9. What Do We Know About Diets Without Fibre?

People following carnivore and other mainly animal-based diets generally consume very little dietary fibre. Some do not eat plant foods at all.

This raises an important question: can people maintain normal digestion and general health without eating dietary fibre?

A survey published in 2021 examined 2,029 adults who identified themselves as following a carnivore diet. The average time participants had followed the diet was longer than a year, although some had followed it for considerably longer.

Participants reported high levels of satisfaction and improvements in their own assessment of their health and various health conditions. [9]

This survey provides information about the experiences of a relatively large group of people following this type of diet. However, the information was self-reported, and the study was not a controlled clinical trial. It therefore cannot establish long-term health outcomes or prove that a fibre-free diet is safe or beneficial for everyone.

A scientific review published in 2026 examined the available human research on carnivore diets. It identified only nine human studies and highlighted problems such as small numbers of participants, short study periods and a lack of controlled research.

The authors concluded that there was not enough reliable evidence to establish the long-term health effects of this type of diet. [10]

This means that we cannot currently establish whether completely avoiding dietary fibre is equally suitable for everyone over the long term.

However, the lack of long-term research does not prove that fibre is essential or that avoiding it necessarily causes harm.

There is a difference between not having enough research to establish the long-term effects of a fibre-free diet and having evidence that the human body must consume fibre.

10. Is Dietary Fibre Necessary?

The available evidence shows that dietary fibre can affect digestion, bowel movements and the activity of bacteria in the large intestine.

However, these effects do not establish that fibre is an essential nutrient.

Official recommendations for fibre are based on particular health outcomes and assessments of population groups. They should not be interpreted as proof that every individual must consume a specific amount.

The history of fibre promotion also deserves attention. Breakfast cereal manufacturers used claims about digestion and disease prevention to market their products, helping make fibre an important selling point. Some of the proposed health benefits were not confirmed by later clinical research.

The research into bran illustrates why these claims need to be examined carefully. Bran can increase stool weight and may affect how often people have bowel movements. However, the available evidence does not establish that it reliably prevents constipation or that everyone needs to eat it to maintain regular bowel movements.

Commercial interests do not automatically make scientific research unreliable, but they make it important to examine who funded the research and whether there were financial interests involved.

At the same time, there is still limited research examining the long-term effects of completely avoiding dietary fibre. It would therefore be premature to claim that a fibre-free diet has been proven equally suitable for everyone.

The important distinction is between something having an effect on the body and something being essential to the body's nutritional needs.

Dietary fibre is not classified as an essential nutrient. Whether an individual chooses to eat it, and how their body responds to it, are separate considerations.

Scientific References

[1] National Academies of Sciences, Engineering, and Medicine. (2017). Guiding Principles for Developing Dietary Reference Intakes Based on Chronic Disease. Washington, DC: The National Academies Press. DOI: 10.17226/24828.

[2] EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA). (2010). “Scientific Opinion on Dietary Reference Values for carbohydrates and dietary fibre.” EFSA Journal, 8(3), 1462. DOI: 10.2903/j.efsa.2010.1462.

[3] Koh, A., De Vadder, F., Kovatcheva-Datchary, P. & Bäckhed, F. (2016). “From Dietary Fiber to Host Physiology: Short-Chain Fatty Acids as Key Bacterial Metabolites.” Cell, 165(6), 1332–1345. DOI: 10.1016/j.cell.2016.05.041.

[4] Gill, S. K. et al. (2021). “Dietary fibre in gastrointestinal health and disease.” Nature Reviews Gastroenterology & Hepatology, 18, 101–116. DOI: 10.1038/s41575-020-00375-4.

[5] “Beauty and the Bran: Kellogg’s Campaign to ‘Correct Faulty Elimination’ and Conquer the Cereal Industry.” (2022). Journalism History, 48(4). DOI: 10.1080/00947679.2022.2125775.

[6] Ippolito, P. M. & Mathios, A. D. (1989). Health Claims in Advertising and Labeling: A Study of the Cereal Market. Federal Trade Commission, Bureau of Economics.

[7] Alberts, D. S. et al. (2000). “Lack of Effect of a High-Fiber Cereal Supplement on the Recurrence of Colorectal Adenomas.” The New England Journal of Medicine, 342, 1156–1162. DOI: 10.1056/NEJM200004203421602.

[8] Chartres, N., Fabbri, A. & Bero, L. A. (2016). “Association of Industry Sponsorship With Outcomes of Nutrition Studies: A Systematic Review and Meta-analysis.” JAMA Internal Medicine, 176(12), 1769–1777. DOI: 10.1001/jamainternmed.2016.6721.

[9] Lennerz, B. S. et al. (2021). “Behavioral Characteristics and Self-Reported Health Status among Adults Consuming a ‘Carnivore Diet’.” Current Developments in Nutrition, 5(12), nzab133. DOI: 10.1093/cdn/nzab133.

[10] Lietz, A., Dapprich, J. & Fischer, T. (2026). “Carnivore Diet: A Scoping Review of the Current Evidence, Potential Benefits and Risks.” Nutrients, 18(2), 348. DOI: 10.3390/nu18020348.

[11] Balk, E. M., Couch, E., Mai, H. J., Chen, Y., Adam, G. P., Kanaan, G., Caputo, E. L., Trikalinos, T. A., Williams, G., Duncanson, K., Talley, N. J. & Lichtenstein, A. H. (2025). “Fiber Intake and Laxation in People With Normal Bowel Function: Systematic Review.” Agency for Healthcare Research and Quality. AHRQ Publication No. 25-EHC037. Rockville, MD: Agency for Healthcare Research and Quality. DOI: 10.23970/AHRQEPCSRLAXATION.

[12] Chang, L., Chey, W. D., Imdad, A. et al. (2023). “American Gastroenterological Association-American College of Gastroenterology Clinical Practice Guideline: Pharmacological Management of Chronic Idiopathic Constipation.” Gastroenterology, 164(7), 1086–1106. DOI: 10.1053/j.gastro.2023.03.214.

[13] Badiali, D., Corazziari, E., Habib, F. I., Tomei, E., Bausano, G., Magrini, P., Anzini, F. & Torsoli, A. (1995). “Effect of wheat bran in treatment of chronic nonorganic constipation: A double-blind controlled trial.” Digestive Diseases and Sciences, 40(2), 349–356. DOI: 10.1007/BF02065421.