In my case, I have to be very careful how much I ingest of any dairy product (including kefir and yogurt, as well as milk). I've found that if I ingest too much dairy for my system (and that is not very much), I get extremely constipated. I'm referring here to cow's milk products. I'm currently experimenting with goat's milk products to see if my experience with them differs. My situation is very surprising to my in-laws, many of whom have a totally opposite reaction when they ingest a dairy product.