I elected to solve the proverb only, but I did it by peeking at the alphametic and knowing that the numbers represented the letters SPONFDMUHR. Yes, I think this is cheating, but I didn't have much time available. In fact, I didn't even check the alphametic, so I hope the puzzle author was careful.
Solution: ONE MAN'S FOOD IS ANOTHER MAN'S POISON
Not used in the proverb: U = 7