If a meal contains 12 g of inulin and 8 g of resistant starch, which physiological property explains why these compounds reach the colon intact to serve as prebiotics?

• A. They bind to bile salts in the small intestine which transports them directly into the hepatic portal vein and then retro-transport to the colon.
• B. They are nondigestible or resistant to human digestive enzymes in the small intestine, so they transit to the colon where microbes ferment them.
• C. They are absorbed through the small intestinal epithelium and then actively secreted back into the colon by colonic epithelial transporters specifically for microbial feeding.
• D. They are rapidly hydrolyzed into simple sugars in the stomach but then re-polymerize in the colon where microbial enzymes reverse the process.

Answer: (B)