Kefir will colonize in the intestines is my understanding. I used commercial kefir and yogurt for 3 years. I bought it by the case thru our buying club. I started seeing an N.A. Dr. who tested my flora. He found "0" good bacteria. I got some kefir grains from a friend and now keep them going on the counter 24/7 our goat is now resting before she gives birth so I am using organic pasturized milk. It works fine enough but I can't wait to go back to the raw. I ferment it 48 hours with the grainsthen I remove the grains and add them to fresh milk while I leave the last batch to ferment another 24 hours shaking it thruout the day. It's pretty tart but it's LOADED.