Polysaccharides: powerhouses for our diet

When you think of carbohydrates, bread, pasta or rice probably come to mind first. But behind these everyday foods lies a whole lot of biochemistry in the form of polysaccharides. These complex molecules play an important role in our body and in our diet.

We got to the bottom of the questions for you about what exactly multiple sugars are all about and what functions and properties they have.

What are polysaccharides?

Polysaccharides, also known as polysaccharides, are complex carbohydrates that are made up of a large number of monosaccharides (simple sugars). The term polysaccharide is made up of the Greek words poly (many) and saccharon (sugar). In biochemistry, they are referred to as polymers, as they consist of many individual building blocks that are linked together by so-called glycosidic bonds.

The general molecular formula for polysaccharides is (C6H10O5)n, where n stands for the number of monosaccharide units. This number can range from a few hundred to several thousand, which shows the enormous diversity and complexity of these molecules.

Types of polysaccharides

There are two main groups of polysaccharides:

Homoglycans consist of only one type of monosaccharide building blocks. Examples of this are starch and cellulose, both of which are made up of glucose units.

Heteroglycans are made up of various monosaccharide building blocks. One example is hyaluronic acid, which is found in our connective tissue.

Five important examples of polysaccharides

Starch: It is the most important energy store in plants and is found in large quantities in potatoes, cereals and rice. Starch consists of two components: Amylose (unbranched) and amylopectin (branched).
Cellulose: As the main component of plant cell walls, cellulose is the most common organic molecule on earth. It gives plants their stability and is an important dietary fiber in our diet.
Glycogen: This polysaccharide serves as an energy store in the human and animal body. It is mainly stored in the liver and muscles.
Chitin: It is an important component of the exoskeleton of insects and the cell walls of fungi. Chitin is also used in medicine and biotechnology.
Pectins: These polysaccharides are found in the cell walls of plants and are used as gelling agents in the food industry.

The structure of polysaccharides

Polysaccharides are formed by linking many monosaccharides via glycosidic bonds. These chemical bonds are formed between the hydroxyl groups (-OH) of two monosaccharides by splitting off a water molecule.

The type of linkage and the number of branches determine the properties of the polysaccharide. For example, cellulose is an unbranched polymer of β-1,4-glycosidically linked glucose units, while glycogen is highly branched and has α-1,4- and α-1,6-glycosidic bonds.

These different structures explain why our body can digest starch but not cellulose. Our digestive enzymes are able to break down the α-1,4-glycosidic bonds of starch, but not the β-1,4-bonds of cellulose.

What is the importance of polysaccharides in nutrition and for the human body?

Polysaccharides play a central role in our diet and have various important functions.

Energy supplier

Starch is a main source of energy for the human body. During digestion, it is broken down into glucose units, which can then be used to produce energy. Starch is found in many plant foods such as cereals, potatoes and pulses. The breakdown begins in the mouth by the enzyme amylase and continues in the small intestine, where the glucose is absorbed into the blood.

Dietary fiber

Indigestible polysaccharides such as cellulose are important dietary fibers. They promote intestinal health, regulate digestion and can help to lower cholesterol levels. High-fiber foods are also recommended for irritable bowel syndrome. Fiber binds water in the intestines, which leads to a larger stool volume and speeds up intestinal transit. They also serve as food for beneficial intestinal bacteria and can therefore reduce the risk of intestinal diseases.

Blood sugar regulation

In contrast to simple sugars, polysaccharides are digested and absorbed more slowly. This leads to a more even rise in blood sugar levels, which is particularly important for people with diabetes. The slow breakdown prevents sharp fluctuations in blood sugar levels and the associated insulin spikes, which can reduce the risk of diabetes-related complications in the long term [1].

Feeling of satiety

Foods that are rich in complex carbohydrates make you feel fuller for longer than those with simple sugars. This is because polysaccharides take longer to be digested and therefore remain in the stomach for longer. In addition, the slower rise in blood sugar levels leads to a lower release of insulin, which in turn suppresses the feeling of hunger for longer.

Prebiotic effect

Some polysaccharides, such as inulin, serve as food for beneficial intestinal bacteria and thus promote healthy intestinal flora. These prebiotic substances are fermented by the intestinal bacteria, producing short-chain fatty acids, which in turn have positive effects on intestinal health [2]. A healthy intestinal flora is not only important for digestion, but also influences the immune system and can even have an impact on mental health.

Which foods contain polysaccharides?

Polysaccharides are contained in a variety of foods, especially those of plant origin, for example:

Cereal products: Wholemeal bread, oatmeal, rice, pasta
Pulses: beans, lentils, peas
Potatoes and sweet potatoes
Corn
Pumpkin
Bananas (contain starch, especially if they are not yet fully ripe)
Nuts and seeds

Important: Not all carbohydrates in these foods are polysaccharides. Bananas, for example, contain both starch (a polysaccharide) and simple sugars such as fructose and glucose.

Are polysaccharides sugar?

Polysaccharides belong to the group of carbohydrates, which also includes sugars. However, they differ significantly in their structure and properties from simple sugars such as glucose or sucrose (household sugar).

Simple sugars consist of one or two monosaccharide molecules and taste sweet. Polysaccharides, on the other hand, are made up of many monosaccharide units and generally have no sweet taste. They are broken down more slowly in the body and therefore have a different effect on blood sugar levels.

From a biochemical point of view, polysaccharides are complex sugar molecules, but in everyday language they are not usually referred to as sugar.

What effects do polysaccharides have on human health?

To save you a tedious Wikipedia search, we have summarized for you what effects polysaccharides can have on our health.

Weight control

Foods rich in complex carbohydrates can help control weight as they satiate for longer and contain fewer calories per gram than fats. Polysaccharides such as starch and fiber have a lower energy density than fats and proteins. In addition, their slow breakdown leads to a more even blood sugar level, which can prevent cravings. High-fiber foods also require more chewing and prolong gastric emptying, which also contributes to satiety. [5]

Gut health

Fiber-rich polysaccharides promote healthy intestinal flora and can reduce the risk of intestinal diseases. Indigestible polysaccharides serve as prebiotics that promote the growth of beneficial intestinal bacteria. These bacteria produce short-chain fatty acids that nourish the intestinal mucosa and have an anti-inflammatory effect. Fiber also increases stool volume and speeds up intestinal transit, which reduces the risk of constipation and diverticulosis. [6]

Cardiovascular health

The consumption of whole grain products, which are rich in complex carbohydrates, is associated with a lower risk of cardiovascular disease [3]. Soluble fiber can lower cholesterol levels by preventing the reabsorption of bile acids in the intestine. In addition, certain polysaccharides such as beta-glucans can lower blood pressure and have an anti-inflammatory effect, which reduces the risk of arteriosclerosis.

Diabetes prevention

A diet high in complex carbohydrates and low in simple sugars can help reduce the risk of type 2 diabetes. Polysaccharides are digested and absorbed more slowly, which leads to a more even rise in blood sugar levels. This reduces the load on the pancreas and can improve insulin sensitivity. Fiber can also slow down the absorption of glucose in the gut, which also contributes to blood sugar control. [7]

Cancer prevention

Some studies suggest that a high-fiber diet can reduce the risk of certain types of cancer, particularly colorectal cancer, and promote intestinal health [4]. The protective effect is attributed to several mechanisms: Dietary fiber accelerates intestinal transit and dilutes potential carcinogens in the intestine. In addition, intestinal bacteria produce short-chain fatty acids during the fermentation of dietary fiber, which have an anti-inflammatory effect and can promote the apoptosis of cancer cells. Some polysaccharides, such as beta-glucans from fungi, also show immunomodulating properties that may contribute to cancer prevention.

Of course, not only polysaccharides are important for human health, but also vitamin A, vitamin B12 and zinc, for example.

Polysaccharides in research, medicine and industry

Certain polysaccharides, especially from fungi and algae, are also used as dietary supplements and show promising results in cancer therapy and in supporting the immune system.

However, the exact mechanisms of action are still the subject of research in chemistry, biochemistry and medicine and further studies are needed to fully understand and utilize the full therapeutic potential of polysaccharides.

The diverse properties of polysaccharides, which are carbohydrate chains linked by glycosidic bonds, also make them interesting for industrial and medical applications:

Food industry: Polysaccharides such as pectins, alginates and carrageenan are used as thickeners, gelling agents and stabilizers. These complex glycans play an important role in texturizing foods.

Pharmacy: Polysaccharides are used as excipients in medicines, for example as coatings for tablets or for the controlled release of active ingredients. Cellulose, an important structural polysaccharide, is often used for these purposes.

Cosmetics: Hyaluronic acid, a glycosaminoglycan, is used in anti-ageing products and moisturizers. Its ability to bind water makes it a valuable ingredient in skin care.

Biotechnology: Polysaccharides such as agarose are used to produce gels for electrophoresis in molecular biology research. This method helps scientists to learn more about the structure and function of oligosaccharides and other biological molecules.

Medical technology: Chitin and its derivatives are used in wound care and for biodegradable implants. These applications utilize the biological functions of polysaccharides in the human body.

The topic of polysaccharides is about much more than the fact that they serve as a source of energy in our food. They are complex molecules that have many functions in nature, in our bodies and in numerous industrial and medical applications. From the structure of plant cell walls to energy storage in the form of glycogen in our bodies and innovative biomaterials: polysaccharides have a wide range of applications!

Sources:

[1] https://pubmed.ncbi.nlm.nih.gov/32186034/
[2] https://pubmed.ncbi.nlm.nih.gov/34119183/
[3] https://herzstiftung.de/infos-zu-herzerkrankungen/blutverduenner-wie-wirken-sie
[4] https://www.allianzcare.com/lebensmittel-die-krebs-vorbeugen-konnen.html
[5] https://pmc.ncbi.nlm.nih.gov/articles/PMC9268622/#sec9-nutrients-14-02641
[6] https://pmc.ncbi.nlm.nih.gov/articles/PMC9573424/
[7] https://pmc.ncbi.nlm.nih.gov/articles/PMC10648557/