Well they absorb through the skin.

The waiting game is a pain. But you have to be patient. Possibly try getting the greens off the ground? If he's nice and fat he can go without food for a while. You dont have to stop food altogether. Just cut him way down and try every other day with greens daily. If they know that the protein is coming they will refuse the greens. Sounds like he's throwing a temper tantrum. That's to be expected.