Wtf? WHO told you that? There's no real food issues involved. :/
When you get a scrape, do you watch your diet then, too? Because that's all a tatt is- just a wound that needs to heal. It just happens to have ink, too. :p If anything, your main concern is just aftercare of the skin.
That's crazy. You should eat so that you don't pass out, but you can eat whatever you want. The only things you should avoid right before getting a tattoo are alcohol & caffeine. They thin your blood & you may bleed in excess during the tattoo. Same thing with aspirin & some other pain medicines.