> The neutral lactate [[salt]] is at least as toxic as the acid form, but each culture varies a little in the amount of acid formed. The enzyme that thickens the [[milk]] sometimes works with very little acid formed. How sour the kefir is suggests how much lactic acid is in it. There are types of yogurt that have much of the acidic whey drained out, that aren't a problem. A spoonful or two of acidic yogurt isn't harmful, but a cupful of the acidic type can be enough to deplete the liver's energy stores, because lactic acid is converted to glucose in the liver, requiring energy. The 'strained' type that isn't acidic is similar to cottage cheese and is safe. > [Is lactic acid a long-term concern with kefiran?] Even dead lactobacilli have an antiinflammatory effect in the intestine, so it’s probably something in their cell wall coat, and kefiran might have a physical effect of that sort.