Oligosaccharides are complex carbohydrates found naturally in various foods. These compounds are short chains of simple sugars, or monosaccharides, typically three to ten units long. They are present in plants, fruits, vegetables, and human milk. Oligosaccharides possess unique properties that contribute to their roles within the body.
Nourishing the Gut Microbiome
Oligosaccharides primarily function as prebiotics, selectively feeding beneficial bacteria residing in the large intestine. These beneficial microbes, such as Bifidobacteria and Lactobacilli, ferment the oligosaccharides that reach the colon undigested. This fermentation process is important for maintaining a balanced and thriving gut microbiome.
The fermentation of oligosaccharides by gut bacteria produces beneficial compounds known as short-chain fatty acids (SCFAs), including butyrate, acetate, and propionate. Butyrate serves as the primary energy source for the cells lining the colon, supporting their health and integrity. Acetate and propionate also play roles in energy production and metabolism throughout the body.
SCFAs contribute to the integrity of the gut barrier, a protective layer that helps prevent harmful substances from entering the bloodstream and strengthens this barrier. A healthy gut barrier is important for overall digestive and systemic well-being.
Supporting Immune Health
Oligosaccharides contribute to the immune system, largely through their influence on the gut microbiome. A healthy and diverse gut microbial community, fostered by oligosaccharides, supports the body’s immune defenses by helping to crowd out harmful bacteria.
Beyond their role in nurturing beneficial gut bacteria, some oligosaccharides may also have direct immune-modulating effects. For instance, certain oligosaccharides can bind to pathogens, preventing them from attaching to the lining of the gut and thereby reducing the risk of infection through a “molecular decoy” function that helps mitigate invading microbes.
The SCFAs produced from oligosaccharide fermentation also play a part in immune regulation. These fatty acids can reduce inflammation in the gut and influence the function of various immune cells.
Sources in Food
Oligosaccharides are present in a variety of common foods. Excellent sources include legumes such as beans, peas, and lentils. Many vegetables, including onions, garlic, leeks, asparagus, broccoli, cabbage, and Jerusalem artichokes, also contain significant amounts. Fruits like bananas, blueberries, and watermelon, along with certain whole grains like wheat and rye, contribute to oligosaccharide intake.
Human Milk Oligosaccharides (HMOs) are a significant source, representing the third most abundant solid component in human milk after lactose and lipids. HMOs are not digested by the infant but instead serve to nourish the infant’s developing gut microbiome. They help establish a healthy gut flora, particularly promoting the growth of beneficial Bifidobacteria.
HMOs also offer benefits for infant immune system maturation. They can reduce the risk of viral and bacterial infections in infants by acting as decoys, preventing pathogens from binding to gut cells. This composition in human milk underscores their role in early life development.
Unique Digestive Journey
Oligosaccharides have unique functional properties due to their journey through the human digestive system. Unlike most other carbohydrates, oligosaccharides are resistant to breakdown by human digestive enzymes in the stomach and small intestine. This means they pass through the upper digestive tract largely intact.
This characteristic allows oligosaccharides to reach the large intestine, or colon, without being absorbed. Once in the colon, they become available for fermentation by the diverse community of gut bacteria. This selective fermentation process is what defines them as prebiotics, specifically nourishing beneficial microbes.
In contrast, most other carbohydrates, like starches and sugars, are broken down into simple sugars and absorbed in the small intestine to provide energy directly to the body. The unique resistance of oligosaccharides to human enzymes is important for their role in modulating gut health and supporting the microbiome.