Inulin: Effects And Properties Of The Prebiotic

Inulin is prebiotic, which means that the substance serves as food for the beneficial intestinal bacteria and can therefore help to build healthy intestinal flora. Below you can read how inulin works, how it is used, and which foods contain it.

Inulin is a special dietary fiber

Inulin is a prebiotic – and therefore a substance that feeds the beneficial intestinal bacteria and contributes to a healthy and balanced intestinal flora. For this reason, inulin is also a frequent component of intestinal cleansing or cures to build up intestinal flora. Because the beneficial intestinal bacteria – which are taken as part of intestinal cures in the form of probiotics – only settle with sufficient food.

Today’s diet usually contains far too few foods with prebiotic properties (e.g. Jerusalem artichoke, black salsify, etc., see list below). The result is that the beneficial intestinal bacteria starve and eventually become weaker and weaker. The harmful bacteria now find more space and spread. While the beneficial bacteria are particularly sensitive to certain dietary fibers, such as e.g. B. Inulin dependent, harmful bacteria can also feed on simple sugars or proteins, so they are much more flexible when it comes to their eating habits.

However, when the less desirable bacteria metabolize proteins, extremely harmful metabolites are formed (e.g. p-cresol, ammonium, etc.). They irritate the intestinal mucosa, have a mutagenic effect (i.e. mutagenic and thus possibly carcinogenic), and put a strain on the immune system.

It is therefore important to provide the beneficial intestinal bacteria with sufficient nutrition in order to prevent the harmful processes mentioned.

Prebiotics or probiotics

The term prebiotics should not be confused with probiotics. A probiotic contains intestinal bacteria, while a prebiotic only contains food for intestinal bacteria. A combination of pre-and probiotics is called a symbiotic.

A prebiotic also does not feed all the motley gut bacteria, but especially the beneficial strains. If the harmful ones were also supplied with it, the corresponding substance should not be called a prebiotic.

The prebiotic inulin, for example, is specifically described as bifidogenic, which means that the substance feeds the bifidobacteria in particular – as has been shown in numerous studies on humans (in different age groups). However, some studies have also shown that taking inulin also increases the number of lactic acid bacteria (lactobacteria). Both groups of bacteria belong to the useful intestinal bacteria and are therefore found in probiotic products to build up the intestinal flora.

Inulin consists of fructose – but the fructose is not digested

Since inulin – a carbohydrate reserve substance in plants – consists of fructose chains, it belongs to the group of fructans. We humans, on the other hand, have glycogen (in the liver and muscles) as a carbohydrate reserve. It belongs to the glucan group because it consists of glucose chains.

The fructose chains of inulin are usually made up of around 35 fructose molecules, with a glucose molecule attached to the end. Shorter fructose chains (up to 10 fructose molecules) are called FOS (fructooligosaccharides, also called oligofructose). They also have prebiotic properties and are found in large amounts in yacon root and its products. Yacon syrup and yacon powder are therefore often used as intestinal-healthy sweeteners.

However, the individual fructose molecules in inulin are now so tightly bound together that a specific enzyme would be required – inulinase – to break these bonds. However, we humans do not have this enzyme. Therefore, the inulin is not digested. Instead, it enters the large intestine undigested. The fructose of the inulin is therefore not resorbed!

Digestible sugars and indigestible sugars

Another example of an indigestible sugar is cellulose. It is the carbohydrate in the grass, wood, or paper and also consists of sugar (even glucose = dextrose and is therefore a glucan). But now you can eat a whole stack of firewood without significant amounts of sugar entering your blood. In cellulose, too, the individual building blocks are so tightly bound together that we humans cannot digest them.

The sugar molecules in an apple, on the other hand, are either free, i.e. completely unbound as free fructose and free glucose, or bound in the form of sucrose. The sucrose bond can easily be broken by our digestive enzymes (glucose and fructose are released). The starch in a roll can also be easily broken down into individual glucose molecules during digestion.

With food, it is not only important whether and how much sugar it contains, but also in which form the sugar is present in this food. Food can therefore be very rich in sugar (cellulose, inulin) without the body being able to “enjoy” the sugar when consuming the food. In these cases, the sugar content is of course not a problem.

The glycemic index or the glycemic load of such foods is then also very low since they hardly affect the blood sugar level at all. For these reasons, indigestible sugars are not referred to as sugar, but as dietary fiber.

Inulin is fermented: Short-chain fatty acids are formed

If the undigested inulin gets from the small intestine to the large intestine, the beneficial intestinal bacteria that live there are happy because inulin is a very special treat for them. Inulin promotes their growth and reproduction and thus the development of healthy intestinal flora. The intestinal bacteria metabolize (ferment) the inulin, producing lactic acid and short-chain fatty acids – butyric acid, propionic acid, and acetic acid.

The effects of short-chain fatty acids

The short-chain fatty acids are now responsible for a large part of the beneficial effects of inulin, as they bring with them the following properties:

• The energy source for intestinal mucosa cells: The short-chain fatty acids are used by the intestinal mucosa cells as an energy source.
• Regeneration of the intestinal mucosa: The short-chain fatty acids promote the regeneration of healthy intestinal mucosa cells and thus the regeneration of the intestinal mucosa. Higher villi (villi), deeper crypts, more goblet cells (cells that make protective mucus), and a thicker layer of mucus form in the colon.
• Protection against leaky gut syndrome: The short-chain fatty acids maintain the barrier function of the intestinal mucosa, thus preventing leaky gut syndrome. (Note: In some places, it is claimed that prebiotics such as inulin could contribute to the leaky gut syndrome. However, this apparently only applies to mice and rats and only if a calcium deficiency is present at the same time. As soon as the animals in the corresponding studies again were well supplied with calcium, prebiotics showed the expected positive effect and the intestinal mucosa recovered.)
• Lowering of the intestinal pH value: The short-chain fatty acids bring about a lowering of the colon pH value to the desired acidic value, which prevents pathogenic germs from settling in the intestine so that the infection rate is also reduced when inulin is administered.
• Anti-inflammatory: The short-chain fatty acids have an anti-inflammatory effect and have even been shown to be helpful in patients with inflammatory bowel disease (see “Inulin and inflammatory bowel disease” below).

Inulin in fructose intolerance

Since inulin consists of fructose chains, people with fructose intolerance often wonder whether they can use inulin or not, especially since many probiotic preparations (yes, almost all of them now) contain inulin as an additive.

However, as we explained above, the fructose chains are not broken down during the digestion of the inulin, so no free fructose is produced either. Nevertheless, inulin is often not a suitable dietary supplement for fructose intolerance – and inulin-rich foods are usually not well tolerated.

In the case of inulin, it is simply because the digestive system of those affected is generally very sensitive to fermentable carbohydrates so the typical symptoms appear for this reason alone.

However, as we also explain below under “Side effects”, inulin has a positive effect on the intestinal flora and thus also on the intestinal mucosa. However, healthy intestinal flora and intestinal mucosa are one of the most important goals, especially in the case of fructose intolerance, so inulin may be helpful in the long term – if you start with tiny amounts – even with FI. Of course, everyone affected has to decide for themselves and try it out if necessary.

Inulin is heat stable

Inulin can either be taken as a dietary supplement in powder form or in the form of foods that are particularly rich in inulin, which you could eat more of immediately. It should be noted here that inulin is heat-stable in a neutral environment, so the corresponding foods can be cooked without losing the beneficial properties of inulin.

Yes, apparently when heating (e.g. when baking) completely new substances can be created from the inulin, which has a far more positive effect on the intestinal flora than the inulin itself, reported food scientists at the TU Dresden in 2006. These are so-called difructose dianhydrides, inulin cleavage products consisting of two fructose molecules, which can also ensure improved calcium absorption.

It is only in an acidic environment (below pH 5) that the fructan would, it is said, be broken down with additional exposure to heat.

Inulin can reduce the risk of colon cancer

It is known from studies that inulin can minimize the risk of colon cancer. As early as April 2005, researchers wrote in the British Journal of Nutrition that inulin has anti-cancer properties. In 12 studies with a total of 29 groups of participants with precancerous lesions or already developed intestinal tumors (the subjects were rats), it was shown that inulin in 26 of the 29 groups can contribute to a significant reduction in the risk of cancer or to a regression of the tumors. Even better results were achieved when prebiotics was combined with probiotics.

The scientists explained that the fermentation of inulin produced substances (including short-chain fatty acids) that prevented pollutants from having a harmful effect on the intestines, which also blocked malignant cell growth and even inhibited metastases. According to the authors, inulin can be described as a protective measure against colon cancer.

In 2013, another study on the effect of inulin on colon cancer risk was published. It showed that inulin could have such a positive effect on the intestinal environment and intestinal flora in animals with a damaged intestinal environment and intestinal flora disorders that the risk of colon cancer fell. Inulin reduced the number of bad bacteria and increased the number of good bacteria. Short-chain fatty acid levels increased and beta-glucuronidase activity decreased.

Beta-glucuronidase is an enzyme that, when overactive, causes toxic substances to be absorbed by the intestinal mucosa and enter the bloodstream. It can also cause carcinogenic substances to form in the intestines in the first place and thus increase the risk of cancer. Elevated beta-glucuronidase levels are therefore currently seen as an indication of an increased risk of cancer.

The strengthening and regulation of the immune system are also one of the tasks of inulin, which on the one hand contributes to successful cancer prevention, but on the other hand of course also protects against other diseases, e.g. B. against autoimmune diseases that are so widespread today, which also include the chronic inflammatory bowel diseases Crohn’s disease and ulcerative colitis:

Inulin strengthens the immune system

After the consumption of inulin, the immune system’s own messenger substances IL-10 and interferon-gamma are increasingly released in the lymphatic tissue of the intestine (in the Peyer’s patches, which represent an important part of the immune system).

IL-10 is an anti-inflammatory messenger substance that regulates the immune system, i.e. also overreactions of the immune system, e.g. B. excessive inflammatory reactions, throttled again. If there is little IL-10 in the intestine, this can promote the inflammation of chronic inflammatory bowel diseases, such as e.g. B. Crohn’s disease and ulcerative colitis. Interferon-gamma, on the other hand, is a messenger substance that stimulates the immune system and makes it strong against viruses and cancer cells.

Inulin can improve chronic inflammatory bowel diseases

In November 2007, a study was published in the Journal of Nutrition examining the influence of inulin on inflammation, intestinal infections, and leaky gut syndrome. According to the researchers, inulin has an extremely favorable effect on the intestinal flora (increases bifidobacteria and lactobacilli, lowers the intestinal pH value, forms short-chain fatty acids, etc.) and therefore prevents gastrointestinal infections and systemic inflammation. Even with chronic inflammatory bowel diseases, inulin can therefore apparently be helpful:

If 18 patients with active ulcerative colitis were given a symbiotic (the combination of prebiotic and probiotic (here Bifidobacterium longum)) for four weeks, the inflammatory values ​​dropped (study from 2004).

In the case of Crohn’s disease, another small study (10 patients) showed that dietary supplementation with 15 g of FOS (i.e. the short-chain fructans) per day led to a positive change in the intestinal flora and reduced disease activity after three weeks. However, the use of inulin in chronic inflammatory bowel diseases should be discussed with the respective doctor, e.g. to choose the right time to take it.

Inulin relieves constipation in children and adults

Of course, inulin also takes care of very obvious gut ailments, such as constipation. In 2- to 5-year-old children suffering from constipation, the daily intake of 2 g of inulin (combined with FOS) resulted in a significant improvement after six weeks, since the prebiotic ensured a softer stool consistency and thus facilitated stool elimination. The study appeared in the International Journal of Food Sciences and Nutrition in 2016.

It is not only the inulin-related intestinal flora regulation that leads to improved stool consistency, but also the fact that inulin is one of the soluble dietary fibers. In a watery environment, these form a kind of gel (as we know it from psyllium husk powder or chia seeds), which loosens the stool. In addition, however, the inulin gel also has a fat-like consistency, so that the intestinal contents become more supple and slippery.

Constipation is also a common problem in older people. A study with 25 participants was published in the American Journal of Clinical Nutrition in 1997. 15 received lactose (milk sugar), and 10 took inulin – each for almost three weeks. You started with 20 g per day, increased continuously from day 9 to day 11 to 40 g, and stayed at this dose until day 19. Inulin was able to relieve constipation better than lactose. The influence on intestinal flora varied greatly from person to person. In general, however, there was an increase in bifidobacteria with inulin, while enterococci and enterobacteria decreased. Lactose, on the other hand, led to an increase in enterococci and a decrease in lactobacteria and clostridia.

Further studies (all from 2000) showed that 10 to 20 g of inulin per day increased the frequency of stools and made the stool soft. However, there was no diarrhea.

In a 2011 randomized, double-blind study published in the International Journal of Food Sciences and Nutrition, subjects (elderly people) who took 15g of inulin daily for 4 weeks also experienced an improvement in their constipation. A significant increase in the intestinal flora was observed, especially the beneficial bifidobacteria. Although some participants experienced slight flatulence, the benefits outweighed the inconvenience and no one stopped taking inulin because of it.

Inulin can regulate lipid metabolism

Inulin is considered a suitable accompanying component for therapies that focus on cholesterol and triglyceride levels. A meta-analysis from 2012 confirmed this after reviewing the studies available up to that point. Inulin lowers LDL cholesterol levels, total cholesterol, and triglycerides in people with correspondingly elevated levels. There was no reduction in people with normal cholesterol and blood lipid levels. Inulin therefore only works where an effect is required.

Two years later, a Spanish study appeared (with almost 1600 participants), which also showed that soluble fiber in particular could reduce blood lipid levels. The higher the consumption of soluble dietary fiber in this study, the rarer were irregularities in lipid metabolism.

We explain the difference between soluble and insoluble fiber in our article on fiber.

Prevent and improve diabetes with inulin

Diabetics in particular often suffer from lipid metabolism disorders, i.e. increased triglycerides. If insulin is missing (insulin this time, not inulin!) or if it doesn’t work properly (insulin resistance), then the triglyceride levels rise. Inulin can therefore initially help diabetics regulate their fat metabolism

support, but also has a direct positive effect on the blood sugar level, as u. a randomized, triple-blind study from April 2013 showed.

49 type 2 diabetics received either 10 g inulin daily or maltodextrin (control group). After two months, the checked blood values ​​of the inulin group were much better than those of the control group. Fasting blood sugar was more than 8 percent lower in the inulin group, long-term blood sugar (HbA1) was more than 10 percent lower, and malondialdehyde was even 37 percent lower than in the control group. (Malondialdehyde is a marker of oxidative stress that is particularly elevated in diabetics.) At the same time, antioxidant levels were nearly 19 percent higher in the inulin group.

Since diabetics often struggle with being overweight, inulin can also be useful in this regard, because it is often used for weight control, as the study from 2015 presented below shows:

Losing weight with inulin

With increasing fat storage in the liver, muscles, and pancreas, the risk of insulin resistance and thus type 2 diabetes increases. One speaks here of ectopic fat because it is not about the typical places of fat storage, such as. B. abdomen or hips.

If this fat is broken down again, the risk of diabetes decreases again. But fat loss in particular is often anything but easy since habits and especially feelings of appetite and hunger are not so easy to turn off. Fermentable carbohydrates such as inulin are considered natural appetite suppressants, leading to reduced food intake and consequent weight loss in obese people.

Interestingly, in animal studies, inulin reduced ectopic fat deposits. Although diets often result in a large loss of weight, this can usually be attributed to the high water excretion. But it would be much more important for health if fat could be broken down, especially ectopic fat, even if this breakdown doesn’t show up on the scales as quickly and massively as the usual water losses.

In the study announced above, 44 people with pre-diabetes took either inulin or cellulose for 18 weeks. In the first 9 weeks, they received four additional nutritional consultations in order to be able to lose 5 percent of their weight, which both groups achieved equally.

In the last 9 weeks, the achieved weight should only be maintained – without further advice. However, the inulin group continued to lose weight here, more so than the cellulose group. The ectopic fat deposits in the liver and muscles had also shrunk more in the inulin group.

This success may have been due to the fact that inulin e.g. promotes satiety and curbs appetite. Inulin expands in the gastrointestinal tract when it forms the gel described above with water. It also slows gastric emptying, which lowers levels of appetite-stimulating hormones, according to a 2016 Canadian study of young healthy women given 6g of inulin with morning yogurt for just eight days. For the reasons mentioned above, inulin is also a component of high-quality weight loss shakes, together with proteins, probiotics, and vital substances.

We describe here that prebiotics can also help with overweight children, which is now so common: Prebiotics for overweight children

Promote calcium absorption and prevent osteoporosis

A lot of fiber can inhibit the absorption of minerals from the intestine. Not so inulin. We had already presented a study here that showed how well inulin can promote mineral absorption and thus improve mineral supply and bone health.

Researchers led by Jessica Campbell discovered in their 2012 study that the administration of inulin to rats led to the animals being better able to absorb calcium and magnesium. Since these two minerals are extremely important for bones, Campbell and colleagues recommend supplementing with inulin to prevent and treat osteoporosis.

A study published in the American Journal of Clinical Nutrition in 2005 confirmed that humans can also benefit from this property of inulin. Young women (who often suffer from calcium deficiency) were given 8 g of inulin daily for a year. Compared to the placebo group, calcium absorption was found to be much better in the inulin group. After one year, bone density was higher in the inulin group than in the placebo group. Since the risk of osteoporosis in later life depends in particular on the calcium supply in youth, it makes sense to take inulin from an early age.

It is believed that inulin also works here via the intestinal flora. Because the healthier the intestinal flora is, the healthier the intestinal mucosa is – and a healthy intestinal mucosa can absorb minerals much better and more extensively, which can be passed straight on to the bone structure. If sufficient amounts of vitamins D and K are available at the same time and the person in question ensures enough exercise, there is almost nothing standing in the way of healthy and strong bones.

Eliminate iron deficiency with the help of inulin

Iron absorption is also promoted in the presence of inulin, particularly from foods containing substances that would normally inhibit iron absorption, researchers said in 2008. A feeding study in pigs (whose digestive systems are very similar to humans) showed that these could only absorb little iron from soy and corn. However, if you gave them inulin in their feed, iron absorption could be increased by 28 percent. Hemoglobin levels also improved. In 2012, another study (this time on rats) confirmed that inulin increased iron absorption.

Inulin can therefore be taken in parallel with iron supplements and/or an iron-rich plant-based diet in order to improve iron absorption and prevent iron deficiency or – if one should exist – remedy it more quickly.

Summary: The effects of inulin

In summary, inulin has the following properties (as this work also shows):

• Inulin improves intestinal health and ensures a healthy intestinal flora
• Regenerates the intestinal mucosa and prevents leaky gut syndrome
• Has an anti-inflammatory effect
• Strengthens the immune system
• Regulates lipid metabolism and blood sugar levels
• Reduces feelings of hunger and excess weight
• Prevents fatty liver by breaking down ectopic fat deposits
• Protects against cardiovascular diseases and diabetes
• Improves mineral absorption and thus bone health
• Ensures healthy development of children

The possible uses of inulin

On the one hand, inulin is a component of many probiotics (here it is filled into capsules together with probiotic bacteria), on the other hand, inulin can also be taken separately in powder form. Of course, the latter has the advantage that the inulin can be dosed individually, especially since there are only very small amounts of inulin in capsules. In the studies listed above, however, 8 to 15 g or more are usually taken per day, which is not possible with probiotic capsules.

Inulin tastes sweet and improves the texture of low-fat foods

Since inulin has a good, slightly sweet taste (it has a tenth of the sweetening power of sugar), it can easily be mixed into a wide variety of dishes, shakes, juices, and smoothies. It does not noticeably change the taste of the original dishes. However, it can change the consistency of the dish. With the help of inulin, foods that are particularly low in fat and sugar are given a consistency that makes you think you are eating a mildly sweetened full-fat product. Inulin can replace oil in sauces or soups without anyone noticing.

So while other sources of fiber tend not to taste so good and their consumption costs some people an effort, the opposite is the case with inulin. It transforms low-calorie foods into tasty ones, naturally without increasing their caloric content or glycemic load.

The correct dosage of inulin

There is no right dosage of inulin. The following applies to inulin: everyone has to test the right dose for themselves. You can do this by starting with very small amounts per day and slowly increasing them. It is extremely important that you always take inulin – like any dietary fiber – with plenty of water/liquid.

Archaeological investigations from 2010 are interesting, which revealed that the indigenous people of the Chihuahuan desert (between the USA and Mexico) frequently consumed inulin-rich desert plants and thus consumed an estimated 135 g of inulin per day, which most people today can no longer tolerate at least not without slowly getting used to these high amounts.

The prebiotic effect of inulin (and FOS) is said to start from a daily intake of 5 to 9 g inulin (in addition to a possible inulin content of the diet), over a period of at least two to eight weeks.

Children under the age of 1 year (including 3- to 6-month-old infants) have been given 1.25 g to 1.7 g of inulin per day in studies.

Whether and which effect occurs depends not least on the existing intestinal flora and its composition BEFORE ingestion. So it may well be that in some people the desired effect occurs even at much lower doses. Researchers also assume that effects occur even if they cannot yet be proven by measurement. For example, it is difficult to prove the increased formation of short-chain fatty acids, since most of these fatty acids are utilized by the intestinal mucosa and are therefore no longer detectable in the stool. Nevertheless, this improves the regeneration of the intestinal mucosa and thus the overall health of the intestine.

Inulin side effects

Inulin is a substance that has little allergy potential and is therefore safe for most people. However, if the intestines are not yet used to fermentable carbohydrates, slight flatulence can occur, which often subsides as soon as the intestinal flora has been regulated with the help of inulin. However, always start with small amounts of inulin and slowly increase them to a dose that is still tolerable for you.

Only people with intolerance to fermentable carbohydrates can react to inulin with increased flatulence and digestive problems. This includes people with fructose intolerance or irritable bowel syndrome. However, this does not apply to all people with this problem. For some, inulin can also contribute to long-term improvement precisely because of its positive properties for the digestive system. To do this, however, inulin must be insinuated very slowly (start with small amounts and increase the dose very slowly). Any inulin intake must also be accompanied by plenty of water.

Inulin is of course not suitable for everyone who practices the so-called FODMAP diet since with this type of diet you e.g. avoids carbohydrates that can be fermented in the intestine.

Inulin for the gut, bones, and overall health

Overall, it can be said that inulin – if well tolerated – offers an easy-to-use and tasty way to improve health. Pure inulin is commercially available as a powder or in capsule form, also in a set with probiotics.

Of course, you can also integrate inulin into any colon or liver cleanse, into any weight loss diet, into any naturopathic diabetes, osteoporosis, fatty liver, or cholesterol therapy, or simply take it as a preventive measure. If you are taking medication at the same time, discuss with your doctor how you could combine the two.