The gastrointestinal tract is the source of many health problems. It may come as a surprise to learn that the gastrointestinal tract is the site of greatest interaction between the individual and the environment. This is because with all the folds upon folds within the intestinal tract, the actual surface area is equivalent to the size of a tennis court! What's more, the intestines and colon are home to hundreds of trillions of tiny bacteria and yeast. Although they only amount to three or four pounds of weight, their numbers are greater than the number of cells comprising the human body, or the number of stars in the universe! This being the case, it makes sense that more than half of the body's immune system is clustered around the gastrointestinal tract. Poor digestion, malabsorption, food decay, weakened immunity, intestinal irritation, blood loss, as well as overgrowth of yeasts, toxic bacteria, and parasites, are all possible causes of poor health that can be identified by analysis of a stool specimen.