Prebiotics are naturally found in many foods, such as beans and lentils, flaxseed, whole grains, and bananas,  or they can be isolated from the plants and added to foods or supplements. Prebiotics stimulate the growth and activity of beneficial intestinal bacteria, known as probiotics, that are associated with health and well-being.  Some probiotic-containing foods are yogurt, kombucha, and kefir.  Also, fermented foods such as tempeh and sauerkraut can bee good probiotics sources.