Bane has to wear a mask, I'm assuming at all times, because it helps him withstand the severe pain. So how does he eat?

Most forum questions are filled with wildly speculative answers, including injection of drugs (which I guess would be the most likely). In the comics, I understand that he originally took Venom, which was the cause of his super-human powers. But could that be enough to supply his body with all the nutrients it needs? (I'm thinking protein especially; he has a lot of muscle.)

Is it ever explained in the comics or elsewhere exactly how Bane receives his nutrition?