1. Bioactive Carbohydrates

The bioactivity of most carbohydrates is mostly dependent on resistance to digestion in the upper gastrointestinal tract (GIT), the stomach, and small intestine. An exception is the disaccharide trehalose, which is composed of two d-glucose units and can be broken down in the small intestine. Trehalose can reduce insulin resistance and improve glucose management in addition to having anti-inflammatory properties. Soluble polysaccharides increase viscosity of the upper GIT content, which enhance trapping of bile acids, preventing cholesterol reabsorption and promoting their removal through the feces. In the colon, the undigested carbohydrates (insoluble fiber, resistant starch, pectins, arabinoxylans, etc.) serve as nutrients for microbes that ferment them into various bioactive products. The fermentation products are usually short-chain fatty acids, which have beneficial effects in improving human health, mostly through anti-inflammatory and anticancer properties. A specific class of polysaccharides that enhance growth of beneficial bacteria in the colon is called prebiotics, mostly fructose-containing polymers. These beneficial bacteria are mostly lactic acid-forming organisms whose growth and multiplication lead to the competitive exclusion of pathogenic microorganisms from the colon. Lastly, certain polyphenols (mostly flavanols) can also act prebiotic agents, and their presence in the diet may contribute to improved gut health.