Simply speaking, polysaccharides (meaning ‘many sugars’) are complex carbohydrates. They are made up of many monosaccharides (single sugars) joined together by glycosidic bonds, which makes them very large, often branched, macromolecules, amorphous, insoluble in water and with no sweet taste.

When all the monosaccharides in a polysaccharide are the same type, the polysaccharide is called a homopolysaccharide. When more than one type of monosaccharide is present, they are called heteropolysaccharides. Some examples of polysaccharides include starch, glycogen, cellulose, and chitin. The term ‘polysaccharide’ refers to those macromolecules that contain ten or more monosaccharide molecules. Polysaccharides such as starch and glycogen consist of several thousand D-glucose units. Relatively lower molecular weight macromolecules, consisting of two to nine monosaccharide molecules, are referred to as oligosaccharides.

From the standpoint of digestion and nutrition, polysaccharides are categorized by whether or not animals make enzymes that allow them to digest polysaccharides into absorbable monosaccharides; for example, starches can be digested by vertebrate enzymes, while fiber cannot. However, beneficial intestinal bacteria can secrete enzymes that digest some types of fiber.

Several major polysaccharides with immune system moderating activity have been isolated from mushrooms—in particular β-D-glucans, polysaccharopeptides (PSP), and polysaccharide proteins. The major immune system moderating effects of these active substances include inducing mitosis and activation of immune cells, such as hematopoietic stem cells, lymphocytes, macrophages, dendritic cells (DCs), and natural killer (NK) cells, resulting in the production of cytokines. The beneficial effects of mushrooms have been associated in many cases with their immune system moderating effects.

In North America, nutritionists used to say that mushrooms were of little food value, based on mushrooms’ low calorie level. This misrepresentation still exists today, due partly to an early lack of complete nutritional information. However, studies done over the past twenty years have shown that mushrooms are an exceptionally good food source, particularly for polysaccharides.

Find plants rich in healthy polysaccharides in Healthy Plant Foods.