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 turn to gel during digestion .
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 chicory, although chicory is the main source for commercial extraction of inulin .
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 .
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 links that are not digestible by the human gut. Therefore, they move slower in the gut, absorb water and swell up like a gel which helps in forming softer stools. This makes them great for digestive health .
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).
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 .
In addition, it increases the number of beneficial bacteria in your gut by acting as their food source .
Health Benefits of Inulin
1) Is a Prebiotic That Increases Good Bacteria
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 [7, 8, 9].
- 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 the bifidobacteria. Eight 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 .
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 .
Therefore, inulin improves gut health in humans by stimulating the growth of beneficial bifidobacteria.
Some studies in bacteria grown in a lab show that inulin also increased bad bacteria such as Salmonella and bacteria that usually don’t cause disease in normal individuals but do cause infections in people with weakened immune systems such as Klebsiella and Escherichia coli (commonly known as E. coli). However, other labs studies show that inulin suppresses the growth of bad bacteria like Clostridium difficile by increasing bifidobacteria growth [13, 14].
2) Reduces Constipation
Due to its ability to swell up after absorbing water, inulin is very effective in reducing constipation. A study (DB-RCT) was conducted in which 17 constipated children, 2 – 5 years of age, were given inulin and their stool consistency was monitored. Children who took these inulin-type fructans had softer stools .
Inulins increase the bulk of the stool by forming a gel-like substance and by increasing beneficial bacteria in the human gut .
3) Helps Reduce Appetite and Prevent Weight Gain
Inulin, when added to low-calorie foods, may be an effective way to suppress appetite and control food intake .
A study (DB-RCT) 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 .
In another study (DB-CT) with 125 overweight and obese adults, a snack bar containing inulin reduced hunger, appetite, and food intake over a 12-week period .
Inulin may help control appetite in several ways:
- By increasing the production of the appetite-suppressing hormone peptide YY [23, 24]
- By increasing glucagon-like peptide-1, a hormone released after a meal that helps in slowing down emptying of the stomach [24, 25]
- By altering the neuronal activity in the brain to suppress the appetite 
4) May Increase Weight Loss
In a study (RCT) of 44 individuals with prediabetes, those who took inulin for 18 weeks lost significantly more weight than those taking cellulose (plant fiber) .
Another study (DB-RCT) of 35 obese women found that inulin-rich yacon syrup decreased body weight and waist circumference .
5) May Reduce Blood Sugar Levels in Type 2 Diabetics
In a study (RCT) 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 .
A meta-analysis of 20 studies (RCTs) and 607 adults participants found that there was a tendency for reduced blood sugar levels in type 2 diabetic patients .
6) Reduces Cholesterol and Improves Heart Health
Inulin improves heart health by decreasing fat levels in the blood through various mechanisms. It :
- decreases the production of liver enzymes that are responsible for making fats.
- increases enzymes that break down fats in muscles.
- enhances the production of short-chain fatty acids.
- alters the production of compounds that increase the production of peptides that make one feel full, and increases the removal of cholesterol in humans and rodents.
In a study (RCT) of 49 type 2 diabetic women, inulin reduced total cholesterol by 12.9% and triglycerides by 23.6% .
A meta-analysis of 15 randomized controlled trials also concluded that dietary inulin-type fructans significantly reduced triglycerides in the blood .
There also seems to be a difference in the effect of inulin on normal subjects versus patients with high cholesterol. Inulin lowers triglycerides in the blood in normal subjects and lowers the cholesterol in patients with high cholesterol .
Since cholesterol clogging the arteries can lead to high blood pressure by making it harder for the heart to pump blood, inulin can be used to reduce or prevent high blood pressure (hypertension) by lowering the cholesterol levels .
7) May Prevent Colon Cancer Development
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 .
Similar results were obtained in mice .
8) May Help Manage Inflammatory Bowel Disease
Studies in humans and animals have shown that inflammatory bowel diseases 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 [40, 41].
9) Increases Calcium and Magnesium Absorption
In a study (DB-RCT) of 15 postmenopausal women treated with either inulins or placebo for 6 weeks, there was an increased absorption of magnesium in the inulin group .
One of the reasons suggested for this is that inulin causes the production of short-chain fatty acids which reduce the pH in the large intestine. This increases the solubility of calcium and magnesium, and they become more available for absorption [49, 50].
10) May Improve Bone Health
In a study (DB-RCT) of 98 adolescents, inulin supplementation for one year increased calcium absorption and bone mineral density compared to controls .
Pregnant mice that were given inulin had thicker bones than mice supplemented with 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 .
Liver Cancer Risk
In mice, inulin introduced in the diet caused liver cancer, but only in mice with a gut microbe imbalance. When given with a high-fat diet, it caused a gut microbe imbalance and liver cancer .
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 kidneys in humans .
However, inulin might have certain side effects in sensitive individuals or if too large a dose is used.
- Intestinal discomfort, including flatulence, bloating, stomach noises, belching and cramping 
- Swelling of the colon 
- Diarrhea 
- 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 .
Also, not enough is known about the effects of inulin supplementation during pregnancy and breastfeeding.
Small intestinal bacterial overgrowth (SIBO) is a disorder where there is excessive bacterial growth in the small intestine. It has been thought that foods that are fermented in the gut, such as inulin, increase small intestinal bacterial overgrowth and should, therefore, be avoided. But recently, it has been shown that prebiotics, such as inulin, are actually beneficial in reducing the symptoms of small intestinal bacterial overgrowth, especially after an antibiotic treatment [58, 59, 60, 61].
It is better to consult with a physician before taking inulin and also start with a smaller dose and increase over time.
Limitations and Caveats
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 .
For individuals with irritable bowel syndrome (IBS), low doses of inulin are recommended since they modulate the gut bacteria and reduce the symptoms. However, larger doses may have a neutral or negative impact on symptoms .
Natural Sources and Forms of Supplementation
Natural sources of inulin are chicory root, Jerusalem artichoke, agave, garlic, jicama, yacon root, sprouted wheat, onions, banana, fresh herbs, and asparagus. Less common sources of inulin are dandelion root, coneflower, burdock root, and camas root.
Inulin supplements are found in various processed foods such as protein and cereal bars, yogurts, baked goods, frozen desserts, table spreads, and dressings. They could 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, 5].
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 .
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 .
A series of clinical studies also show that up to 20 g/day of inulin and/or oligofructose is well tolerated and effective .
The best way to start taking inulin is to consume foods that are rich in inulin or oligofructose. If you need to supplement with additional inulin, you can start with 2 – 3 g per day for at least 1 – 2 weeks, after which you can increase the amount to 5 – 10 g a day depending on your tolerance. You can increase it up to 20 g/day based on the results of a clinical trial .
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 noted that inulin caused brain fog and acid reflux in addition to bloating and gas.
Some users recommend starting off with a small dose (1 – 3 g) and gradually increasing it. They also note that the bloating and gas symptoms that occur at the beginning of supplementation slowly disappear after a few weeks of supplementation.
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