If you listen to the Trim Healthy Mama podcast I linked in the Q&A section, they talked about how it doesn't matter if you use really good quality milk or not. You can use cheap milk from Walmart or dollar store if you have to, and the kefir grains eat up all the "bad" stuff in the milk (hormones, etc.). Amazing! But if you want you can use the good milk, the only thing I read is NOT to use ultra pasteurized milk.