When cheese is made, most of the fat and casein proteins go into the curds;
most of the sugar and whey proteins stay in the water  The lactose is
dissolved in the water. The split is not perfect. The curds literally
contain water. Part of what the aging process does is squeeze the water
out. Water is expensive to ship, so food processors almost universally use
dried whey rather than the liquid (also known as sweet liquid whey). (The
federal rules allow either liquid or dried whey to be reported as whey on a
food ingredients list.) Dried whey is extremely high in lactose. Whey
protein concentrate, as the name implies, is less so (up to 80% protein).
Whey protein _isolate_ is less than 0.5% lactose and may be lactose free.
There are yet other whey variants with yet different amounts of lactose.
But any dried dairy product (dried milk, dried buttermilk, etc.) should be
assumed to be high in lactose.

As always, my apologies for the way these messages come out formatted. I'm
thinking of changing e-mail vendors, with the hopes that may solve it.

Steve Carper