that is not true. the myth stems from frequent yeast infections in tongue piercings. bread contains the wrong kind of yeast. beer also contains the wrong kind of yeast. the over-use of Listerine is the leading cause of yeast infections in oral piercings. eat whatever you want, but i would stay away from spicey or acidic foods as they can irritate thepierings.
look here http://www.safepiercing.org/piercing/ for proper aftercare and what to avoid
I'd say its safe.