Oligosaccharides are a type of carbohydrate. They are distinct from simpler sugars and more complex carbohydrate structures. These compounds are gaining increasing attention for their diverse roles in biological systems and their potential to support human health.
What Makes an Oligosaccharide
Oligosaccharides are carbohydrates composed of a small number of monosaccharide units linked together. The term “oligo” means “few,” as they typically contain three to ten monosaccharide units. These units are joined by glycosidic bonds.
This distinguishes them from monosaccharides (single sugar units like glucose) and polysaccharides (much larger chains). Their arrangement, type, and linkage configuration determine an oligosaccharide’s unique structure and properties. Oligosaccharides can exist freely or be attached to other molecules like proteins or lipids, forming glycoconjugates such as glycoproteins and glycolipids.
Key Types and Natural Occurrences
Several types of oligosaccharides occur naturally. Fructooligosaccharides (FOS) are common in plants, including bananas, onions, chicory root, garlic, asparagus, and jicama.
Galactooligosaccharides (GOS) occur in dairy products, legumes, and certain root vegetables. Human Milk Oligosaccharides (HMOs) are uniquely found in human breast milk, the third most abundant solid component after lactose and lipids.
Essential Biological Functions
Oligosaccharides play diverse roles in biological systems. A prominent function is their role as prebiotics, nourishing beneficial gut bacteria. Unlike other carbohydrates, most oligosaccharides are not digested in the upper gastrointestinal tract and travel intact to the colon, where they are fermented by beneficial microorganisms like Bifidobacteria and Lactobacilli. This fermentation supports a healthy gut microbiota, which in turn produces beneficial compounds like short-chain fatty acids (SCFAs).
Beyond their prebiotic effects, oligosaccharides are involved in cell recognition and communication. They are often found on the surface of animal cells, attached to glycoproteins or glycolipids, where they act as markers for cell-to-cell signaling. For example, oligosaccharides on red blood cells determine ABO blood types. Human Milk Oligosaccharides (HMOs) also contribute to immune system development and protection against infections by acting as decoys, preventing pathogens from binding to host cells. Additionally, some oligosaccharides have demonstrated immunomodulatory effects, influencing immune cell responses.
Practical Uses and Health Benefits
The unique properties of oligosaccharides have led to their application in various practical settings, especially within the food and supplement industries. Their ability to serve as prebiotics makes them valuable ingredients in functional foods and dietary supplements. They are commonly added to infant formulas to mimic some of the beneficial effects of human breast milk on gut health and immune development in infants.
Consuming oligosaccharides offers several potential health benefits, largely stemming from their prebiotic activity. These benefits include improved digestive health by supporting a balanced gut microbiome. They may also contribute to a stronger immune system, partly by fostering the growth of beneficial bacteria that help defend against harmful pathogens. Beyond gut health and immunity, research suggests potential benefits such as enhanced mineral absorption and improved blood sugar regulation.