ISSA Nutritionist Practice Exam

Gut bacteria primarily prefer which type of carbohydrate?

1. Simple sugars

2. Cellulose

3. Starch

4. Fiber

The correct answer is: Cellulose

Gut bacteria primarily prefer fiber, particularly dietary fiber, because it is a type of carbohydrate that is not fully digested by human enzymes. Unlike simple sugars and starch, which can be broken down and absorbed by the body, fiber passes through the digestive system relatively intact. Many gut bacteria, particularly those in the large intestine, have evolved to utilize fiber as a food source. They ferment soluble fiber, producing short-chain fatty acids (SCFAs) that provide various health benefits, including improved gut health, increased satiety, and potential anti-inflammatory effects. Fiber is categorized into soluble and insoluble types, both of which play essential roles in gut health. Soluble fiber is particularly significant because it can be fermented by gut bacteria, leading to the aforementioned benefits. On the other hand, simple sugars and starches are more easily digested and absorbed in the upper gastrointestinal tract, which leaves less for the gut microbiota to feed on. While all carbohydrates can be significant to human nutrition, fiber is uniquely favorable for supporting a healthy and diverse gut microbiome.