Evidence Based
9

9 Health Benefits of Inulin Fiber + Side Effects & Dosage

Written by Carlos Tello, PhD (Molecular Biology) | Reviewed by Biljana Novkovic, PhD | Last updated:
Jonathan Ritter
Puya Yazdi
Medically reviewed by
Jonathan Ritter, PharmD, PhD (Pharmacology), Puya Yazdi, MD | Written by Carlos Tello, PhD (Molecular Biology) | Reviewed by Biljana Novkovic, PhD | Last updated:

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Inulin Fiber

Inulin is a type of fiber found in plants that is made up of the simple sugar fructose. Research shows it can improve regularity, lower blood sugar and fat levels, and increase weight loss. Read on to see other potential benefits of inulin and how to take it without experiencing side effects.

What Is Inulin?

Inulin (not to be confused with insulin, which is a hormone that controls blood sugar levels) is a type of soluble fiber found in a variety of plants. Fibers are compounds that are not digested or absorbed by the human gut. Soluble fibers attract water and are turned into gel during digestion [1].

Inulin is present in 36,000 plant species including those we consume in our daily diets such as wheat, onion, bananas, garlic, and asparagus. They are also found in less common foods such as Jerusalem artichokes and especially chicory, the main source for commercial extraction of inulin [2].

Plants containing inulin use it to store energy and as a protection against cold temperatures. When exposed to cold temperatures, inulin acts as an antifreeze [3].

Components

Inulin is made up of a string of fructose molecules (like beads on a string) with glucose on either end. However, these molecules are linked in the chain by bonds that are not digestible by the human gut. Therefore, they move slower in the bowel, absorb water, and swell up like a gel that helps in forming softer stools [4].

The number of fructose molecules in each string (beads) can vary from 2 to 60. Inulin is called high-performance inulin when it contains more than 10 molecules of fructose strung together. When they are manufactured commercially, the shorter chains are removed from the product. Chains that contain less than 10 molecules are called fructooligosaccharides (FOS).

Fructooligosaccharides have a sweet, pleasant flavor and are used to supplement foods with fibers [5].

Mechanism of Action

Inulin’s solubility allows it to absorb a lot of water. As it swells up, it forms a gel that gathers fat particles along the way and takes them out of the body [4].

In addition, it increases the number of beneficial bacteria in your gut by acting as their food source (prebiotic) [4].

Natural Sources

Natural sources of inulin are chicory root, Jerusalem artichoke, agave, garlic, jicama, yacon root, sprouted wheat, onions, bananas, fresh herbs, and asparagus. Less common sources of inulin are dandelion root, coneflower, burdock root, and camas root.

Snapshot

Proponents

  • Acts as a prebiotic
  • May reduce constipation
  • May lower blood sugar and fat levels
  • May help lose weight
  • May help increase calcium and magnesium absorption
  • May help with IBD
  • May help prevent colorectal cancer

Skeptics

  • Some potential benefits have been insufficiently investigated
  • May cause digestive issues in some people
  • Unknown safety profile during pregnancy
  • Increased the incidence of liver cancer in mice

Health Benefits of Inulin

Effective as:

Prebiotic

Inulin acts as prebiotic by being a non-digestible food ingredient that feeds the good bacteria in the gut [2, 6, 7].

The human gut contains trillions of beneficial bacteria (probiotics). Bifidobacteria are good bacteria that occupy the lower gut (colon). They ferment complex carbohydrates that cannot be digested in the upper gut and releases short-chain fatty acids (such as butyrate) that are essential for human health [8, 9, 10].

Inulin is basically food for bifidobacteria and stimulates their growth and activity. Good bacteria have a number of important functions in our bodies. They [10, 11, 5]:

  • produce acetic acid and lactic acid, which lowers the pH of the colon and prevents the growth of bad bacteria in the gut.
  • stimulate the immune system.
  • aid the absorption of certain minerals.
  • increase the production of B vitamins, such as folate, B12, thiamine, and niacin.

Multiple studies have shown that inulin stimulates the growth of bifidobacteria. For instance, 8 healthy subjects were given fructooligosaccharide instead of sucrose for 15 days and their stools were monitored. Although the total number of bacteria in their stool did not change, bifidobacteria became the predominant type [12].

In another study, 10 constipated elderly patients were given inulin for 19 days and their stools were monitored. These patients also showed an increase in the bifidobacteria numbers with a simultaneous decrease in harmful bacteria [13].

Therefore, inulin improves gut health in humans in part by stimulating the growth of beneficial bifidobacteria.

Other bacterial groups also seem to be impacted by the consumption of inulin. In a clinical trial on 165 people, this fiber also increased the abundance of Anaerostipes (which may improve digestion and even protect from colon cancer by producing butyric acid) and reduced Bilophila (which are associated with harder stools and constipation) [14].

Some studies in bacteria grown in a lab show that inulin also increased bad bacteria such as Salmonella and those that don’t cause disease in normal individuals but may cause infections in people with weakened immune systems such as Klebsiella and Escherichia coli (commonly known as E. coli). However, other lab studies show that inulin suppresses the growth of bad bacteria like Clostridium difficile by increasing bifidobacteria growth [15, 16].

Likely Effective for:

1) Reducing Constipation

Due to its ability to swell up after absorbing water, inulin is very effective in reducing constipation. A study was conducted in which 17 constipated children, aged 2-5 years, were given inulin and their stool consistency was monitored. Children who took these inulin-type fructans had softer stools [17].

Multiple studies have also shown that inulin increased the frequency of stools and their consistency in adults [18, 19, 20].

Inulins increase the bulk of the stool by forming a gel-like substance and by increasing beneficial bacteria in the human gut [21].

The evidence suggests that inulin may help with constipation. You may discuss with your doctor if it may be helpful in your case. Remember that inulin should never be taken in place of what your doctor recommends or prescribes for constipation.

2) Lowering Blood Sugar

In a study of 49 type 2 diabetic women, supplementation with inulin significantly reduced fasting blood sugar (by 8.5%) and HbA1c (by 10.4%), an indicator of the average blood sugar levels over the previous three months [22].

Milk powder containing inulin and resistant dextrin lowered blood sugar levels before and after meals, insulin resistance, and blood pressure in a clinical trial on over 100 elderly people with type 2 diabetes [23].

In another trial on 60 middle-aged people with this condition, supplementation with inulin and butyrate (but not with inulin alone) for 45 days reduced blood sugar levels before meals [24].

A meta-analysis of 20 studies and 607 adults participants found that there was a tendency for reduced blood sugar levels in type 2 diabetic patients [25].

Again, the evidence suggests that inulin may help lower blood sugar levels in people with type 2 diabetes. However, it shouldn’t be taken instead of prescribed antidiabetic medication. You may discuss with your doctor if it may help as an add-on to your treatment regime.

3) Lowering Blood Fats

Inulin may decrease fat levels in the blood through various mechanisms. It may [26]:

  • decrease the production of liver enzymes responsible for making fats.
  • increase enzymes that break down fats in muscles.
  • enhance the production of short-chain fatty acids.
  • Increase satiating peptides and cholesterol removal.

In a small trial on 22 healthy men, pasta enriched with inulin reduced blood triglycerides by 22.2% while increasing HDL (“good”) cholesterol by 35.9% [27].

In another trial on over 200 adults with high blood cholesterol, an inulin-enriched soymilk drink reduced total cholesterol by 6.6% and LDL (“bad”) cholesterol by 10% but had no effects on triglycerides and HDL (“good”) cholesterol [28].

In a study of 49 type 2 diabetic women, inulin reduced total cholesterol by 12.9% and triglycerides by 23.6% [22].

A meta-analysis of 15 randomized controlled trials concluded that dietary inulin-type fructans significantly reduced triglycerides in the blood [29].

There seems to be, however, a difference in the effect of inulin on normal subjects versus patients with high cholesterol. Inulin tended to lower blood triglycerides in normal subjects and cholesterol in those with high levels of this fat [30].

To sum up, the evidence suggests that inulin may help lower blood fat levels (especially triglycerides in healthy people and cholesterol in those with high levels). You may discuss with your doctor if taking inulin may help you lower your blood fat levels.

Possibly Effective for:

Overweight

Inulin, when added to low-calorie foods, may be an effective way to suppress appetite and control food intake [31].

A study in 40 women showed that consuming 16 g per day of inulin-type fructans in the morning for 7 days curbed appetite and helped reduce food intake during lunch [32].

In another study with 125 overweight and obese adults, a snack bar containing inulin reduced hunger, appetite, and food intake over a 12-week period [33].

Similarly, incorporating inulin into food products reduced appetite and slightly increased energy expenditure at rest in a clinical trial on 21 overweight but otherwise healthy people [34].

However, 10 g of inulin before meals was ineffective at suppressing appetite in a small trial on 7 overweight middle-aged and elderly adults [35].

Inulin may help control appetite in several ways:

  • By increasing the production of the appetite-suppressing hormone peptide YY [36, 37]
  • By increasing glucagon-like peptide-1, a hormone released after a meal that helps in slowing down stomach emptying [37, 38]
  • By altering brain activity to suppress the appetite [39]

These are most likely the results of increased short-chain free fatty acids [36, 37, 39], but there are also studies that question their involvement [40].

Dietary inulin may also help lose weight.

In a study of 44 individuals with prediabetes, those who took inulin for 18 weeks lost significantly more weight than those taking cellulose (plant fiber) [41].

Another study of 35 obese women found that inulin-rich yacon syrup decreased body weight and waist circumference [42].

Taken together, limited evidence suggests that inulin may help with overweight by reducing food intake and helping burn fat. However, other lifestyle interventions such as doing more exercise or improving your diet may be safer and more effective. You may use inulin as a complementary approach if your doctor determines that it may be helpful in your case.

Insufficient Evidence for:

1) Increasing Calcium and Magnesium Uptake

Four studies in 14 women, 9 men, 13 young men and women, and 59 adolescent girls found that supplementation with inulin increased calcium absorption and retention [43, 44, 45, 46].

Similarly, chicory inulin increased blood calcium levels in a clinical trial on 46 diabetic women [47].

However, 2 studies on 12 healthy men and 14 adolescent girls found inulin ineffective at increasing calcium uptake [48, 49].

In a study of 15 postmenopausal women treated with either inulins or placebo for 6 weeks, there was an increased absorption of magnesium in the inulin group [50].

Inulin also increased magnesium absorption and retention in rats [51, 52].

One of the reasons suggested for this is that inulin causes the production of short-chain fatty acids that reduce the pH in the large intestine. This increases the solubility of calcium and magnesium, which then become more available for absorption [53, 54].

Taken together, a few, small clinical trials (with mixed results in the case of calcium) and some animal research are insufficient to claim that inulin increases calcium and magnesium uptake. Larger, more robust clinical trials are needed to shed some light on this potential benefit.

2) Bone Health

In a study of 98 adolescents, inulin supplementation for one year increased calcium absorption and bone mineral density compared to controls [55].

Similarly, an intervention with 8 g/day of inulin-type carbohydrates improved bone calcium absorption (but only in 32 out of 48 adolescents) in another trial [56].

However, a beverage fortified with inulin had no effect on bone resorption in a clinical trial on 15 middle-aged, wheelchair-bound people [57].

Pregnant mice that were given inulin had thicker bones than mice supplemented with a regular diet or a calcium-enriched diet. The offspring of mice given inulin also had increased bone mineral density compared to the offspring of mice in the other groups [58].

Again, a few, small clinical trials with mixed results and an animal study cannot be considered sufficient evidence that inulin improves bone health. Further clinical research is needed.

3) Inflammatory Bowel Disease

Studies in humans and animals have shown that inflammatory bowel diseases may result from some human bodies not tolerating the resident gut bacteria. In such cases, prebiotics such as inulin can be used to reduce inflammation in the gut [59, 60].

In a small trial on 19 people with ulcerative colitis, dietary inulin was well tolerated and reduced indigestion symptoms and bowel inflammation (measured as stool calprotectin levels) [61].

In another trial on 18 people with this condition, the combination of inulin with beneficial gut bacteria (Bifidobacterium longum) for a month reduced bowel inflammation and blood inflammatory cytokines (TNF-alpha and IL-1alpha) [62].

However, the results of clinical trials on using inulin to treat Crohn’s disease, another type of inflammatory bowel disease, were inconclusive [60, 63].

A study in mice showed that inulin reduced the inflammatory cytokine IFN-gamma while increasing the anti-inflammatory IL-10. This reduced gut inflammation in these animals [64].

Once again, the evidence is insufficient to support the use of inulin in people with IBD, especially in the case of Crohn’s disease. More clinical trials on larger populations are needed.

4) Preventing Colon Cancer Development

In a clinical trial on 37 people with colon cancer and 43 who had undergone the surgical removal of polyps in the colon, an intervention with an inulin-enriched prebiotic and beneficial bacteria (Lactobacillus rhamnosus and Bifidobacterium lactis) reduced colorectal proliferation and increased IFN-gamma production in those with cancer. In those with removed polyps, it reduced exposure to bacterial toxins and an inflammatory marker (IL-2) [65].

Rats that fed diets containing inulin had more beneficial bacteria, such as bifidobacteria while rats that fed on normal diets had more harmful bacteria. Inulin prevented the incidence of chemically-induced colon cancer in these rats [66].

Similar results were obtained in mice [67].

Inulin, when used in combination with beneficial microbes, also decreased colon cancer risk in rats [68, 69].

Although the results are promising, most of the research has been done in rodents. More clinical trials are needed to confirm these preliminary findings.

Side Effects & Precautions

This list does not cover all possible side effects. Contact your doctor or pharmacist if you notice any other side effects.

Call your doctor for medical advice about side effects. In the US, you may report side effects to the FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch. In Canada, you may report side effects to Health Canada at 1-866-234-2345.

Inulin is safe when used as recommended. It has a generally recognized as safe (GRAS) status from the US Food and Drug Administration (FDA).

In fact, due to its safety, it has been used to measure the filtration rate of human kidneys [70].

However, inulin might have certain side effects in sensitive individuals or if too large a dose is used.

These include:

  • Intestinal discomfort, including flatulence, bloating, stomach noises, belching and cramping [71]
  • Swelling of the colon [72]
  • Diarrhea [72]
  • Although rare, severe allergic reactions can occur. In some isolated cases, it has resulted in an allergic reaction, possibly linked to a food allergy response [73].

Also, not enough is known about the effects of inulin supplementation during pregnancy and breastfeeding. Pregnant women should therefore avoid inulin supplements.

Small intestinal bacterial overgrowth (SIBO) is a disorder where there is excessive bacterial growth in the small intestine. Foods that are fermented in the gut, such as inulin, have long thought to increase bacterial overgrowth in the small intestine. But recently, prebiotics such as inulin were found to be actually beneficial in reducing the symptoms of this condition, especially after an antibiotic treatment [74, 75, 76, 77].

Inulin may not be suitable for all individuals. It is rapidly fermented in the colon by bacteria. The resulting product draws up the water in the colon and releases gas. This is particularly a problem for individuals with irritable bowel syndrome (IBS), who might experience gas and bloating [72].

For individuals with irritable bowel syndrome (IBS), low doses may modulate the gut bacteria and reduce the symptoms, but larger doses may have a neutral or even negative effect [78].

It is better to consult with a physician before taking inulin and also start with a small dose and increase over time.

Liver Cancer Risk

In mice, inulin introduced in the diet caused liver cancer, but only in those with a gut microbe imbalance. When given with a high-fat diet, it worsened microbe imbalance and increased the incidence of liver cancer [79].

Limitations and Caveats

The effects of inulin on calcium and magnesium absorption, bone health, IBD, and colorectal cancer prevention have only been investigated in a few, small clinical trials (some of them with mixed results) and animal studies. Further clinical research on larger populations is needed to confirm their preliminary results.

Supplementation

Forms

Inulin supplements are found in various processed foods such as protein and cereal bars, yogurts, baked goods, frozen desserts, table spreads, and dressings. They can be in the form of native inulin (usually extracted from chicory), high-performance inulin (containing only the longer chains), oligofructose (containing only the shorter chains) and fructooligosaccharides (containing short inulin molecules made from table sugar) [5].

Dosage

In the United States, most individuals consume far less dietary fiber than the daily value (DV) set at 25 g. The average daily consumption for inulin and oligofructose is estimated to be between 1 and 4 g in the United States, with a higher intake of 3 g to 11 g seen in Europe [80].

Doses up to 10 g/day of inulin obtained from natural sources and up to 5 g/day of oligofructose were well-tolerated in healthy, young adults [81].

A series of clinical studies also showed that up to 20 g/day of inulin and/or oligofructose was well tolerated and effective [80].

The best way to start taking inulin is to consume foods that are rich in inulin or oligofructose.

Because inulin supplements are not FDA-approved, there is no official dose for them. Users and supplement manufacturers recommend to start with 2-3 g per day for at least 1-2 weeks and increase the dose to 5-10 g/day up to 20 g/day depending on tolerance. Discuss with your doctor if inulin may be useful as a complementary approach in your case and which dose you should take.

User Experiences

The opinions expressed in this section are solely those of inulin users, who may or may not have medical or scientific training. Their reviews do not represent the opinions of SelfHacked. SelfHacked does not endorse any specific product, service, or treatment.

Do not consider user experiences as medical advice. Never delay or disregard seeking professional medical advice from your doctor or other qualified healthcare providers because of something you have read on SelfHacked. We understand that reading individual, real-life experiences can be a helpful resource, but it is never a substitute for professional medical advice, diagnosis, or treatment from a qualified healthcare provider.

One user noted that, after a few months of inulin supplementation, their triglycerides went down by 33% and their total cholesterol decreased slightly. They did, however, experience minor bloating and gas.

Another user reported that inulin caused “brain fog” and acid reflux in addition to bloating and gas.

Some users recommended starting off with a small dose (1-3 g) and gradually increasing it. They also noted that the bloating and gas symptoms that occur at the beginning of supplementation slowly disappear after a few weeks of supplementation.

About the Author

Carlos Tello

Carlos Tello

PhD (Molecular Biology)
Carlos received his PhD and MS from the Universidad de Sevilla.
Carlos spent 9 years in the laboratory investigating mineral transport in plants. He then started working as a freelancer, mainly in science writing, editing, and consulting. Carlos is passionate about learning the mechanisms behind biological processes and communicating science to both academic and non-academic audiences. He strongly believes that scientific literacy is crucial to maintain a healthy lifestyle and avoid falling for scams.

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