text: probiotics question? what are probiotics? are they safe? what should i look for when purchasing a probiotic and are there any brands that are highly recommended?   also, do probiotics work on the small intestines or is it only effective on the large intestines? they are good bacteria. they aid in digestion and fight bad bateria.  yes, they are safe.  gnc? they are a good and reliable brand.  always check the expiry date.  i think they work when in the stomach and small intestines and usually do not reach the large intestines.  the website below is also helpful.