What is inulin?
Inulin, sometimes also called chicory root fiber, is another type of polysaccharide stored in plants in addition to starch. Structurally, inulin is a "linear" polysaccharide composed of n fructofuranose units and a small amount of pyranosyl glucose, with a degree of polymerization ranging from 2 to 60. Therefore, inulin is, in fact, a genuine mixture of various sugars.
Fun Fact:
What is the degree of polymerization? The degree of polymerization refers to the number of repeating units in a macromolecule polymer. The more repeating units, the higher the degree of polymerization, meaning the molecule is larger. Conversely, the smaller the degree of polymerization, the smaller the molecule. To use an imperfect analogy, imagine if the number of segments on a centipede's body was not fixed: fewer segments would result in a small centipede, while more segments would create a large one. In this case, the number of segments can be understood as the degree of polymerization.
Inulin is highly stable, heat-resistant, and easily soluble in water, yet it cannot be digested by the human stomach or intestines. In other words, when we consume inulin, it gets metabolized by the beneficial bacteria in our gut, which then produce various secondary metabolites.
As a prebiotic, inulin is one of the safest and most effective dietary supplements. It has been approved for use in foods in many countries for quite some time.
Where exactly does inulin come from?
In fact, 99.99% of people are unaware of this. Many assume that since it's called "inulin," it must naturally be extracted from chrysanthemums, but this is a misconception.
Inulin has a wide variety of sources, with the most common being from plants, though it can also be extracted from some microorganisms, albeit less frequently. You might be surprised to learn that foods you may not be fond of, like garlic and onions, are rich in inulin. Additionally, bananas contain a high amount of inulin, which explains why eating bananas might help with constipation—it's not pseudoscience.
Currently, the high-purity inulin widely used in food products both domestically and internationally is extracted from plants in the Asteraceae family (chicory family). However, the situation differs between countries. In China, much of the inulin is extracted from Jerusalem artichokes (also known as sunchokes), while in other countries, inulin is primarily sourced from chicory root.
Inulin can help lower blood lipids
The benefits of inulin include increasing the abundance of Bifidobacteria and other beneficial bacteria in the gut microbiota, assisting in lowering blood sugar levels, and promoting the absorption of nutrients such as vitamin D, iron, and calcium, among others.
A 2016 study compared the effects of inulin with different degrees of polymerization on lipid metabolism. The results showed that inulin with varying degrees of polymerization significantly lowered blood lipids, including total cholesterol, triglycerides, and liver triglycerides. Additionally, cecal blood flow was significantly improved.
Another study also demonstrated that inulin can reduce total cholesterol and low-density lipoprotein (LDL) cholesterol levels in the serum of test animals. However, the conclusion clearly stated that the results were only effective in obese mice on a high-fat diet, with little to no lipid-lowering effect observed in mice with lower body weight.
Inulin not only lowers bad cholesterol but also raises good cholesterol. For example, adding inulin to staple foods resulted in a 36% increase in high-density lipoprotein (HDL) levels and a 23% decrease in triglycerides after just 5 weeks of intervention.
This raises a crucial question: How does inulin regulate lipid metabolism? Or, put differently, why do prebiotics like inulin have lipid-lowering effects?
In fact, prebiotics like inulin share similar benefits. First, inulin can "bind" with fats in the gut to form a stable latex complex. This complex is difficult for lipases and other enzymes to further metabolize, leading to its excretion, thus preventing the formation of triglycerides and other metabolic byproducts.
Second, inulin improves the gut microbiota and regulates lipase levels. Many beneficial gut bacteria can influence the levels of lipases in the gut, such as Bifidobacteria and Lactobacilli, while reducing bacteria that may contribute to obesity, like some Firmicutes strains.
Over time, these effects lead to a gradual reduction in blood lipids.
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