INULIN: STRUCTURE, PROPERTIES, FOODS, CONTRAINDICATIONS - BIOLOGY - 2025

The inulins (β - (2,1) fructans, fructose oligosaccharides) are carbohydrate compounds 2 to 60 fructose units which are synthesized by several plant families "upper" and some microorganisms. Since they do not generate an increase in the glycemic response, they are considered “suitable for diabetics”.

Inulins have been known since about 1804, when Valentine Rose isolated the first ones from the roots of "elecampana" or "helenium" (Inula helenium) and then, in 1817, Thomas coined the term "inulins" to refer to these molecules.

Basic structure of an inulin (Source: NEUROtiker via Wikimedia Commons)

They are often found in "commercially important" plants such as endive, banana, onion, garlic, barley, rye, wheat, among others, so they are common compounds in food preparations consumed by man for a long time. many years.

Its industrial production began in Europe in the early 1900s and started from endive roots produced in Holland and Belgium.

They are routinely used as a replacement for fats and sugar (they have more or less 10% of the sweetening power of common sugar), they are used as stabilizers and as thickening agents, especially in those preparations that are based on dairy products, in the bakery and in meat preparations.

Many authors consider them a type of soluble "fiber" from vegetables that has multiple benefits for human health when it is included in food or when it is ingested directly for medicinal purposes.

Structure

Inulins are carbohydrates, so they are essentially made up of carbon, oxygen and hydrogen atoms, which assemble cyclic structures that form chains by joining each other consecutively.

Generally it is a "polydisperse" mixture of fructose oligosaccharide chains (C6H12O6, an isomer of glucose) whose length varies depending on the source from which they are obtained and the conditions of production.

Commonly, inulins are made up of "short" chains of fructose residues (up to 10 units) linked through fructofuranosyl β- (2 → 1) bonds, which is why the term "oligofructose" is sometimes used to describe them, being their average length of about 4 residues for shorter ones and up to 20 for longer ones.

Representative structure of fructan molecules (Source: User: Ayacop via Wikimedia Commons)

However, there are also very long chain inulins, which can be made up of more than 50 fructose residues. The average molecular weight of inulins is around 6000 Da and plants use it as an energy reserve.

Regardless of the chain length they have, many inulins have a terminal glucose residue (it forms a sucrose), although it is not a defining characteristic for these types of compounds.

Bacterial inulins

Inulins that have been identified in microorganisms such as bacteria show high degrees of polymerization, which implies that fructans with considerably longer chains than those found in plant organisms have been obtained.

In addition, these carbohydrates in bacteria have 15% more branches in their main structure, which is why they are said to be a bit more "complex" structurally speaking.

Properties

Groups

Inulins are part of the group of carbohydrates known as “the group of fermentable mono-, di-, oligosaccharides and polyols” (FODMAP, from the English Fermentable Oligo-, Di-, Monosaccharides and Polyols), which when digested mediate income of water in the colon.

Solubility

The solubility of inulins depends, to a large extent, on their chain length or "degree of polymerization", being those with longer chains more "difficult" to dissolve.

Stability

They are very stable molecules at high temperatures, up to 140 ° C; but they are quite susceptible to acid hydrolysis, that is, at a pH lower than 4. The most common commercial presentation consists of an off-white powder whose particles are quite "clear" or "translucent" and normally have a neutral taste.

Viscosity

Many authors state that solutions abundant in inulins are not viscous, however, when these are mixed with other molecules they can compete with other polysaccharides to bind to water molecules, which causes a change in their "rheological behavior" (in solution).

Thus, it has been shown that when their concentration in a mixture exceeds 15%, inulins can form a kind of "gel" or "cream", whose strength varies depending on the concentration, temperature and length of the chain. of fructose residues (those of greater length form firmer gels).

When used in conjunction with thickening agents (xanthan, guar gum or pectins), inulins function as "homogenizers". In addition, these substances can provide "fat-like" characteristics to gum-based and fat-free culinary sauces and dressings.

Hygroscopic

They are very hygroscopic molecules, that is, they hydrate easily, which is why they also act as wetting agents.

Inulin Intake Benefits

Since these carbohydrates provide the human body with only 25 or 35% of energy, they are considered "suitable for diabetics", as they do not significantly influence the increase in blood sugar levels (glycemia).

These starch-like substances are prescribed by mouth for those patients with very high levels of cholesterol and triglycerides in the blood, but they are also popular for:

- contribute to weight loss in obese patients

- relieve constipation, especially in children and the elderly

- relieve diarrhea and other major conditions like diabetes

- the treatment of celiac disease (contributes to the absorption of vitamins and minerals)

The medicinal use of these substances is very common and the doses correspond to 12-40 g per day for up to 4 weeks for the treatment of constipation; 10g per day for 8 days for the treatment of diabetes; 14 g per day for the treatment of high blood cholesterol and triglyceride levels; and 10 to 30 g per day for 6-8 weeks to treat obesity.

Additionally, although not fully proven, inulins have been shown to be helpful in maintaining heart health, mineral absorption and bone health, preventing colon cancer and certain inflammatory bowel diseases.

Mechanism of action

Many authors propose that inulins are not absorbed in the stomach, but rather are "sent" directly to the intestines (posterior or large intestine), where they function as food for some of the symbiotic bacteria of the human gastrointestinal system, therefore they help them grow and reproduce.

This is because the bonds that join the fructose units in these carbohydrate polymers cannot be hydrolyzed by stomach or intestinal enzymes, which is why these compounds are considered "probiotics", since they directly feed the intestinal flora.

A probiotic is any ingredient that allows specific changes both in the composition and / or in the activity of the gastrointestinal microflora that confers benefits for the health of the host that harbors them.

Bacteria capable of feeding on inulins are those that are directly associated with intestinal functions and general health.

These are capable of converting inulins, as well as other “probiotic” substances, into short-chain fatty acids (acetate, propionate and butyrate), into lactate and into some gases, which, together, can nourish the cells of the colon.

In addition, it is thought that these carbohydrates destabilize the synthesis mechanisms of some body fats, which directly influences their reduction (treatment of obesity).

Inulin-rich foods

Inulins have been described as natural components of more than 3,000 different varieties of vegetables. In addition, they are widely used in the food industry as a dietary supplement, and also as an additive to improve the physical and nutritional properties of many preparations.

As discussed above, the most common sources of inulins are:

- escarole roots

- Jerusalem artichoke, Jerusalem artichoke or pataca

- the tubers of dahlias

- the yacón

- asparagus

- the onions

- the bananas

- the garlics

- leeks

- wheat and other cereals such as barley

- stevia, among others.

Photograph of endive roots (Source: See page for author via Wikimedia Commons)

Other sources

Inulins can also be found as food supplements in capsules or powders and also in commercial preparations such as protein bars, cereals, in yogurts, etc.

They are usually found as native escarole extracts:

- as “oligofructose” (where the longer chain inulins are removed), - as “HP” or high-performance inulins (from the English High-performance; from which the shorter chain inulins are eliminated) and

- such as "FOS" or fructo-oligosaccharides (which are produced from table sugar).

Contraindications

Literature reviews indicate that oral inulin consumption is relatively safe when used appropriately.

However, with the consumption of more than 30 grams a day the main side effects are observed at the gastrointestinal level, since there may be the production of gas, bloating, diarrhea, constipation or abdominal cramps.

When consumed with food, inulins are safe for pregnant or lactating women, although not enough studies have been conducted to determine whether their medicinal consumption may have any adverse effect on the mother or infant, so it is recommended avoid it.

Likewise, inulins can be safely consumed by children, adolescents, adults and the elderly, either as an integral part of food or as a short-term medicinal supplement.

References

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