Inulins—plant fibers composed mostly of fructose—travel through the intestines without being fully digested and are a food source for bacteria in the large intestine. Some beneficial bacteria, such as bifidobacteria and lactobacilli, thrive in the presence of dietary inulins and other indigestible fibers known as prebiotics. Healthy colonies of these gut bacteria can have many positive effects on colon and overall health.
A number of studies show that healthy people and people with digestive problems generally benefit from inulins in the diet and in supplements, but with very high intakes, inulins can cause gas and digestive discomfort. Some people experience gas and bloating even with small amounts of inulins; in some cases this may mean they don’t have strong colonies of beneficial gut bacteria.
Source: The American Journal of Gastroenterology