According to Lisa Guy, nutritionists, to maintain optimal health of the digestive system of the important things is a healthy balance of intestinal flora or good bacteria. These bacteria are necessary for the body to keep the digestive system healthy and maintain immune function, as quoted from Body and Soul, Saturday (29/03/2014):
Overgrowth of bad bacteria (including yeast and parasites) are generally caused by poor diet, stress, excessive use of antibiotics, or excessive alcohol consumption.