Inulin / Chicory Root Fiber - Everything You Need To Know

ITF is a broad term meant to include FOS, inulin, oligofructose, oligofructose-enriched inulin, etc. Greg Kelly summarized it well in a review article where he breaks down precisely how inconsistent these terms get used throughout the research world.

What is inluin, chicory root fiber and their ITF friends?

When defining each ITF, a lot of it comes down to chemical and molecular compounds, degree of polymerization, and processing. Even commercially available inulin may be inconsistent due to processing, sourcing, and labeling.1

To try to simplify the issue, here’s an analogy:

Imagine you’re in a grocery store aisle with all apple-like products. First, you pick up a ‘pink lady’ --or is it a ‘Cripps pink?’ One expert calls it a pink lady apple, the other calls it a Cripps pink apple. They’re both similar, and some experts say they’re the same type of apple, while other experts say they’re different. Then you pick up a Granny Smith apple, still an apple, but better for making pies than other apples due to their chemical makeup. Then it gets more complicated. There are apple sauces, apple butter, apple extract, and other ‘apple-type products.’ Some apples are different depending on the time of year harvested, and some apple sauces are different depending on the processing.

This isn’t a perfect analogy, but hopefully, it helps you understand the complexity and bigger picture of inulin-type fructans. 

ITF’s are members of a larger group called “fructans.”1

Fructans may sound familiar to you if you have read up on the Low FODMAP diet. Fructans are one of the ‘FODMAPs’ that should be avoided if you have IBS due to their potential negative side effects in people with IBS (more on this later).

The term inulin-type fructan is generally used to be all-encompassing for inulin, FOS, oligofructose, oligofructose-enriched inulin, etc. While ITF’s are not exclusively from chicory root, the studies mentioned generally source their ITFs from chicory root.2,3 

Summary of ITF’s:

• Inulin: a type of fiber that is extracted from plants, like chicory root, artichoke, etc. 
• Inulin is soluble, non-viscous, and fermentable4 
• The characteristics of inulin give it a smooth, creamy texture and provide a fat-like mouth feel and are used to replace fat in a variety of food products (baked goods, dairy, dressings, etc.).
• Oligofructose: produced through partial hydrolysis of inulin
• Soluble, ferments more quickly in the colon
• Functional properties similar to sugar or glucose syrup and provides 30-50% sweetness as table sugar
• Added to foods to add sweetness with fewer calories and increased fiber
• FOS: an inulin-type fructan synthesized enzymatically from sucrose
• Others: Inulin HP, FOS-enriched inulin, FOS-enriched inulin HP, oligofructose-enriched inulin, and oligofructose-enriched inulin HP

Inulin is present in >36,000 plant species. It is estimated that Americans consume on average 1–4 g of inulin and oligofructose per day, and Europeans average 3–10 g/d. The chemical structure of inulin prevents it from being digested like a typical carbohydrate and is responsible for its reduced caloric value and dietary fiber effects.5

As you can see in the table below,6 chicory root is a major source of inulin. 

In this article, we will discuss the proposed benefits of ITF’s on humans.  Here’s the summary:

Health benefits of inulin & chicory root fiber

• Appetite and weight management: There are trends that inulin may affect weight and appetite in overweight and obese people, but the evidence is poor.
• Bowel Function: Some evidence implies that inulin may benefit people by increasing the frequency of bowel movements, but constipation can be a little more complicated than that.
• Microbiome: inulin is recognized as a prebiotic with bifidogenic effects. It has been shown to increase propionate and acetate, but not butyrate. 

Potential Benefit: Appetite and Weight Management

It is theorized that inulin and oligofructose may positively affect appetite and body weight. In animal studies, ITFs have been shown to modulate certain hormones that affect satiety. The idea is that inulin’s ability to increase SCFAs creates a chain reaction that decreases your appetite, which reduces caloric intake, and induces either weight loss or decreases the amount of weight gained over time.7 

Unfortunately, weight loss is never as simple as ‘take this and lose weight.’ So far, the evidence linking ITF consumption and satiety is poor, and the evidence is limited on ITF’s effect on body weight. Two studies conducted with overweight and obese adults showed significant weight reductions in their participants; however, several studies have shown no significant difference.8,9

One reason for this could be due to the differences in specific ITF’s. A specific type of ITF may be more effective than another type of ITF when it comes to weight loss. Another consideration for decreased intake with ITF’s could be adverse reactions. Common complaints of ITF consumption are flatulence and bloating, which for some, may lead to decreased intake at a given meal.9

Potential Benefit: Bowel function

It is thought that the SCFA production caused by inulin or ITFs accelerate recovery and regenerate the intestinal wall, as well as lower colonic pH, which may stimulate the growth of beneficial microflora and inhibit the growth of pathogens. More studies with specific inulin types are needed to establish whether dietary fiber, through diet or supplementation, can play a role.10 

The patients who received 24 g/day of inulin had increased butyrate levels and reduced inflammation in the intestines compared to the patients who did not receive inulin.11 When patients were given oligofructose-enriched inulin in doses of 4 g three times/day, fecal calprotectin, a marker for intestinal inflammation, was significantly reduced.12 

IBS

Bifidobacteria are generally lower in people with IBS compared with healthy individuals. Considering ITF’s bifidogenic effects, you could conclude that ITF supplementation may cure or reduce symptoms in IBS patients. However, there are currently few studies that investigated the effect of prebiotics on people with IBS. 

Two studies in adults with IBS at doses of 6 g/day of oligofructose and 20 g/day of inulin showed no improvement in symptom or stool output measures. Another trial showed improved symptoms with 5 g/day of short-chain FOS, but this study had poor participation, and the results are not definitive.14,15

It should be noted that inulin, or any ITF, are not allowed on the Low FODMAP diet, a diet that is used to mitigate gastrointestinal symptoms in people with IBS (read more about that here). Two studies where the Low FODMAP diet (a diet with very low ITF’s) decreased IBS symptoms also reduced bifidobacteria (significantly in one study). The other study showed an increase in stool pH, which is thought to have a negative impact on the gut.15 More research is needed for the use of specific prebiotics in the treatment of IBS symptoms. For example, it would be interesting to see a study done on an ITF that slowly ferments in the distal gut and how it affects individuals with IBS. 

Constipation

Constipation is generally defined as having less than 3 stools per week. However, constipation can involve more than just frequency in stools, such as pain, stool bulk or incomplete evacuation, and water content. 

Chicory root or inulin may be helpful with increasing the numbers of stools passed in a given time. Inulin has been shown to increase stool frequency in doses of 12, 15, 20, and 40 grams per day in constipated study subjects. A study where participants received 15 g/day of chicory inulin resulted in softened stool; however, the other studies did not show significant differences in stool consistency.16,17 

If someone is having 3 small hard stools a week, takes an inulin supplement, and now has 5 small hard stools per week, that may not be the best outcome available. On the other hand, Psyllium is well researched in its ability to ease constipation symptoms, and you can read more about it here (link to psyllium article). Psyllium is generally well-tolerated, whereas inulin may cause bloating at dosages as low as 2.5-5 g/day for some people.18

Potential Benefit: Inulin and the Microbiome

Bacterial Growth

Where inulin really stands out is its potential function as a prebiotic (The word prebiotic describes fibers that are selectively used by the microbiome for a targeted effect). ITF’s have proven again and again to have a bifidogenic effect (increase bifidobacteria in the gut). A review article assessed 9 studies that showed how inulin affects the microbiome, and in all 9 studies, inulin increased bifidobacteria. The review article noted that some study results showed that inulin may affect the microbiome in other ways, such as increasing lactobacillus, faecalibacterium, anaerostipes, and even decreasing Bacteroides,  although these results were less consistent.26  

Inulin’s Effect on Bacterial Growth in the Microbiome26 

Different bacteria affect the gut and health in different ways. A lot is still unknown, but here’s what we know so far: 

• Bifidobacteria: Increases resistance to infection, immune-enhancement, anti-carcinogenic, vitamin production, secrete antimicrobial compounds27 
• Lactobacillus: B Vitamin synthesis, Antitumor activity, Toxin neutralizing effect, cholesterol-lowering activity, antioxidant activity, immune modulation, pathogen inhibitor.28 
• Faecalibacterium: An important butyrate producer that is found in lesser amounts in people with IBD, people with colorectal cancer, the elderly, and in the presence of inflammation.29,30,31,32  
• Bacteroides: lower levels found in people with IBD, coronary artery disease, transient ischemic attack (mini-stroke), and atherosclerotic ischemic stroke. One of the most prominent bacterial genera in the gut, usually beneficial, but can also become pathogenic if they escape the gut. Thought to reduce oxygen levels in the gut, allowing for anaerobic bacteria (SCFA producers) to persist.33,34,35 

The big takeaway here is that inulin increases bifidobacteria, which, as you can see, has some potential benefits.

SCFA Production

Inulin’s ability to increase SCFA levels have mixed results. Some studies have shown that inulin has no effect on SCFA production, while others have shown to increase SCFA levels, specifically acetate and propionate. Others have shown an increase in butyrate, no effect on butyrate, and even a decrease in butyrate.26,36,37 A continuing theme is that the effects on inulin on SCFA production varied by individuals, reminding us that each microbiome is unique, and how the individual responds to certain fibers (or any food) is likely dependent on their unique microbiome landscape.

The chart below are some individual studies that we reviewed. :

Adverse Effects

The most reported side effect of ITF supplementation is flatulence. Other possible side effects include abdominal pain, bloating, cramps, and diarrhea.43 One study concluded that 10 g/day of inulin and 5 g/day of oligofructose are well tolerated without adverse effects44; however, bloating has been reported with daily doses as low as 2.5-5 g, and abdominal pain has been reported at doses as low as 10 g daily.18 Another study claims that ITFs at 20 g/day are safe but will cause some GI symptoms, mostly flatulence. Toxicity levels have been studied in mice, but the upper limit in adults has not been established.45 The FDA has stated that 20 g/day of FOS is generally recognized as safe.21 

Several reports indicate that long-chain ITFs may be more tolerable than low-chain ITFs, which could be attributed to the slower and more stable fermentation of long-chain ITFs. A number of different factors can change whether an ITF is long-chain vs short-chain such as plant source, harvest time, climate condition, etc.45 A single ITF, say inulin, can differ in its chain length depending on processing, while oligofructose and FOS are generally defined by their short-chain.1 More experimental work is needed for further safety evaluation and tolerance for the use of ITFs.

Big Takeaways

• Defining each individual ITF is complicated and inconsistent throughout the research. Supplement companies should clearly label and explain what type of ITF they are selling so that the consumer can make an educated decision in taking the supplement. 
• Due to the low tolerability of inulin (gas production), if you want to include more inulin in your diet, this can be done by eating more inulin-containing foods like garlic, onions, artichoke, asparagus, and wheat.
• Inulin may have beneficial effects for those with ulcerative colitis and diabetes. Inulin can be included either by diet or supplemented. Always talk to your doctor before taking a supplement for medical purposes. 
• For those who suffer from constipation or high cholesterol levels, inulin is not the most effective fiber. The FDA has approved Psyllium to claim its cholesterol-lowering effects and has been clearly studied with easing constipation symptoms.
• Inulin has been shown to have prebiotic effects by its ability to increase bifidobacteria. This is likely beneficial but is dependent on your personal gut landscape.