NANP Board Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

Fructooligosaccharides (FOS) are a type of carbohydrate categorized as prebiotics, which means they are non-digestible fibers that promote the growth of beneficial microorganisms in the gut. The small intestine is primarily responsible for the digestion and absorption of nutrients. However, fructooligosaccharides resist digestion by enzymes in the small intestine because they are not broken down into single sugars. As a result, they escape degradation in this part of the digestive tract and stimulate beneficial bacteria as they pass into the large intestine.

The large intestine is where FOS truly acts as a prebiotic. It is in this region that they are fermented by gut microbiota, leading to their beneficial effects. Thus, while they do escape degradation in the small intestine, their primary prebiotic activity occurs in the large intestine.

Understanding that fructooligosaccharides are not absorbed in the small intestine is crucial for recognizing their role in gut health. This is why the small intestine is significant—FOS must pass through it unaltered before reaching the fermentation sites in the large intestine where they exert their health benefits.