IMO, most storebought "kefir' should not be called kefir. Real kefir grains are highly complex, balanced ecosystems containing over thirty beneficial micro-organisms. You can not use even real kefir as starter for additional batches of kefir, as you can with yogurt. Real kefir can only be brewed from the actual grains themselves. Most commercial kefir contain ten or so mico-organisms, plenty of lactose, and even added sweeteners. Real, fully ripened kefir has a ph of 4, all of the lactic acid, and none of the lactose. Read Dom's Kefir Page. Calling kefir grains "a miracle of nature" is no exaggeration. If anything, it's an rank understatement.