Leaving Certificate Digestion Practice Test 2026 - Free Digestion Exam Practice Questions and Study Guide

Symbiotic bacteria in the gut produce vitamins that our bodies can’t make in sufficient amounts on their own. They particularly synthesize vitamin K and several B vitamins, which are then absorbed and used throughout the body for processes like blood clotting and energy metabolism. This vitamin-producing role is a direct and well-established function of the gut microbiota. While these bacteria do aid digestion and help defend against pathogens in other ways, the most straightforward function described here is vitamin production. Absorbing water is mainly handled by the intestinal lining, with bacteria playing a less direct role.