Bacteria are just about everywhere in the environment as well as in, and on, us. They live throughout the human gut but the greatest concentrations are in the large intestine (bowel) where up to 1000 species of bacteria can be found.
We should aim to maintain a healthy balance of bacteria within the gut. This balance can be disturbed by a number of factors including antibiotics, stress, poor diet and living conditions, concurrent diseases and allergic reactions. Probiotics and prebiotics are agents employed in restoring the balance and/or protecting against disruption.