Apparently there are two ways recommended by LLL to decrease milk supply -
Oral contraceptive pills with estrogen and progesterone and
drinking sage tea! 
Steep one tablespoon of fresh whole leaf dried herb in one cup of boiling water for 10 to 15 minutes. Drink three cups a day until it has decreased to the desired level.
Well there you go. What other foods do you reckon, Jenni?