The mention of Vitamin D no longer being added to margarine (which I never eat) made me look up values for butter. It's the most abundant vitamin in butter! One tablespoon (14 grams) provides about 11% of the Reference Daily Intake (RDI). Methinks Mother Nature knew what she was doing. Fat soluble vitamins belong in fatty real foods.

If they are using the Adult RDA of 600 IU, that would be only ~66 IU per tablespoon, but it is a start. Of course the real foods highest in Vit D content are all animal products, which "health" gurus tell people to shun.