Inulin

Inulin is a type of natural chemical found in many plants. Plants make inulin to store energy, often keeping it in their roots or underground stems. Unlike some plants that store energy as starch, these plants choose inulin instead.

Inulin belongs to a group called dietary fiber, specifically a type known as fructans. In 2018, the United States Food and Drug Administration allowed inulin to be used in foods to improve their nutritional value. Because of this, you might find inulin added to many processed food products today.

Inulin is also special because doctors use it to check how well kidneys are working. When they need the most accurate way to measure kidney function, they use inulin as the best comparison method.

Origin and history

Inulin is a natural energy source found in more than 36,000 kinds of plants, such as agave, wheat, onion, bananas, garlic, asparagus, Jerusalem artichoke, and chicory. Plants use inulin to store energy and to help them survive cold weather. Because it can dissolve in water, inulin helps plants control the amount of water inside their cells, which can protect them during cold or dry times.

Inulin was first found in 1804 by a German scientist named Valentin Rose. He discovered it in the roots of a plant called Inula helenium. Later, scientists studied its structure and found useful ways to separate it. Inulin is also used by doctors to measure how well the kidneys are working.

Chemical structure and properties

Inulin is made up of chains of a sugar called fructose. These chains are connected in a special way that our bodies cannot break down easily. This means inulin does not give us many calories and acts like dietary fiber, which is good for our health.

Inulin has no color or smell, so it does not change how food tastes or looks. Some types of inulin are a little sweet, similar to table sugar, while others are not sweet at all. Inulin mixes well with liquids and can create a thick, creamy texture like fat. This helps keep foods stable and can also help with making foams and mixtures stay mixed.

Uses

Harvesting and extraction

Chicory root is the main source for getting inulin for commercial use. The process to get inulin is similar to how we get sugar from sugar beets. After harvesting, the chicory roots are sliced, washed, and soaked in a solvent like hot water or ethanol. The inulin is then separated, cleaned, and dried. Inulin can also be made from sucrose.

Processed foods

Inulin is safe to use in foods, as approved by the U.S. Food and Drug Administration. It is used in many processed foods because it works well in manufacturing. It can add fiber to foods and tastes only a little sweet—about 10% as sweet as sugar. Inulin can replace sugar, fat, and flour in recipes. It has less energy than regular carbohydrates and can help the body absorb important minerals like calcium and possibly magnesium. It also helps good bacteria grow in the digestive system.

Medical

Inulin is used by doctors to check how well kidneys are working. This is done by measuring how much fluid the kidneys filter each minute. Although inulin is the best way to do this test, it is not used often because it is expensive and needs many blood samples over several hours.

Possible side effects

When eaten in larger amounts, inulin can cause some stomach problems like bloating, gas, and diarrhea. People who are allergic to inulin might also have stomach inflammation.

Industrial use

Inulin can be turned into ethanol, a type of fuel, through a special process. This could help make fuel from plants that have a lot of inulin.

Biochemistry

Inulins are special kinds of sugars made mostly from a sugar called fructose. They are formed by linking fructose units together in a straight chain, with just a tiny bit of branching. These chains can be short with just a few fructose units, or very long with up to around 200 units. When inulins are broken down, they can form shorter chains called fructo-oligosaccharides.

Inulins can have a small piece of another sugar, glucose, at the end, or they might not. Scientists have special names for these different types, but the main idea is that inulins are stored forms of energy in many plants.

Calculation of glomerular filtration rate

Inulin is special because it passes through a part of the kidney called the glomerulus but is not changed by other parts of the kidney. This makes inulin useful for measuring how much blood the kidneys filter each minute, called the glomerular filtration rate (GFR).

Doctors used to use inulin a lot to measure GFR, but now they use other, simpler ways. These include measuring things like creatinine in the blood and urine. Inulin has to be given to a person through an infusion, which can be a disadvantage, but it is helpful because doctors know exactly how much inulin is given.

Metabolism in vivo

Inulin is a type of fiber that our bodies cannot break down easily. It moves through most of our digestive system without being digested. Only in the lower part of the digestive system, called the colon, do special tiny living things called bacteria break down inulin. This process releases gases like carbon dioxide, hydrogen, and methane.

Inulin is a soluble fiber, meaning it dissolves in water. Soluble fibers can help keep our blood health good by possibly lowering cholesterol and sugar levels. Because our body cannot break down inulin into simple sugars, it does not raise blood sugar levels, which can be good for people with diabetes. Inulin also helps friendly bacteria in our gut grow. It moves through the stomach and the first part of the small intestine without being digested, making it ready for the bacteria in the gut to use.

Some traditional foods contain a lot of inulin, like chicory, garlic, and leek, and these have been valued for good health for many years. Studies have shown that inulin can cause some stomach problems like bloating and gas, but it might also help prevent certain travel illnesses and improve how the body absorbs important minerals like calcium.

Natural sources

Many foods contain inulin, a special kind of sugar stored by plants. Some of these foods include chicory root, which has up to 18 grams per 100 grams, and Jerusalem artichoke with up to 13 grams per 100 grams. Other foods with inulin are dandelion greens, garlic, leeks, onions, asparagus, wheat bran, barley, and bananas.