Probiotics are described as being living micro-organisms which, upon ingestion, affect the body in a beneficial manner. The human bowel contains a complex population of bacteria of several hundred different species and thousands of subspecies. These bacteria, and the chemicals they produce, can have a negative or a positive effect on the human body within which they live. The 'good' bacteria found in the human bowel are known as normal flora. This normal human flora is considered beneficial to the body as these bacteria aid in the breakdown of proteins and fats in food and help with the metabolism of vitamins, minerals and amino acids. They control infective bacteria from implanting via a number of mechanisms, and in addition, the good bacteria appear to boost the immune system and protect us from pathogenic (bad) bacteria penetrating the bowel wall and infecting the host, the human body. In fact they can stimulate immune responses beyond the gut positively improving skin and respiratory tract immunity, for example.

Problems arise if pathogenic or bad bacteria implant or live among the good human flora. This can cause an imbalance which can have a debilitating and toxic effect on the bowel or even the entire body. Probiotics can include normal human flora which are introduced into the body to increase their dominance in the bowel, thereby reversing the damage and associated problems caused by bad bacteria. Although transient passage of cultured probiotics can improve symptoms it should be noted that oral probiotics commercially available are incapable of implanting permanently into the gut flora as they have lost their capability to adhere to epithelial cells through the process of culturing in the commercial laboratory. It is only fresh human probiotics from another human being that retain that capability and hence can be implanted to reverse damage and side effects and then stay in the bowel to protect in the future.