Nutrient composition of milk vs. home-made kefir I got a bit confused when looking up nutrition values for milk versus kefir made from that milk. For some reason many tables list higher values of some nutrients (e.g. potassium and magnesium) than is in the source form, i.e. the milk.

Can someone shed light on how this would happen?

I realize that lactose from the milk gets turned into carbon dioxide and alcohol, but where does it take the additional nutrients from if the only nutrition for the kefir grains is the milk and air?
It could just be the difference in milk sources. Different cows, receiving variable types of feed, produce milk with varying nutritional content. They probably only tested kefir using milk from one or at most two sources. In comparison, the figures for normal milk could be drawn from hundreds of dairy farms across the nation.

I would expect there to be changes in the carb/protein/fat content of the milk, as well as vitamins produced/consumed by the kefir.  Specifically, the carbohydrate level should be lower from lactose being digested into lactic acid.