I can assure you that probiotics and prebiotics are very safe and healthy, in fact they are what make yogurt so healthy. Probiotics and prebiotics work together to build and develop the microflora in your GI tract to increase absorbtion of nutrients and the defend the body from harmful bacteria or viruses. Probiotics are the actual cultures (like lactobacillus acidophillus) that are added to the food to ensure the proper cultures are present in the intestine, whereas the prebiotics are oligosaccharides that feed the cultures.