The mucus layer covering the epithelial surface of the gastrointestinal tract serves as the front line of protection against the luminal contents and plays a key role in the establishment and activity of the commensal microbiota. The composition and complexity of the bacterial community within this environment is altered by the introduction of fermentable dietary components. These dietary components can change the metabolic end products of bacterial fermentation, which in turn are able to modify the expression of mucin genes and proteins leading to an increase in the mucus layer thickness. This review introduces some of the key interactions between fermentable carbohydrates, commensal bacteria, and intestinal cells which influence mucin production.