From NAKAIMA Genkai 仲井真元楷's Okinawa kotowaza jiten (沖縄ことわざ辞典, "Dictionary of Okinawan sayings"), which I picked up in Osaka, a.k.a. the Plague Zone, over the weekend:
禽獣は殺しても食べられるが 人は殺しても食べられぬ
ichimushi-ya kuruchiN kamarii-shiga chu-ya kuruchi-ya kamaraN
"Kill an animal, and at least you can eat it; you can't eat people even if you kill them."
(Pardon my possibly misleading transcription of Nakaima's Okinawan—he provides it as furigana alongside the Japanese, but I'm not really hip to the consensus on how to romanize it.)
The intended point here, according to Nakaima, is that life is precious and human life the most precious of all. I'm just not sure that focusing on the frustration of the thwarted would-be cannibal is the best way to get this across.
The first half of "ichimushi" is cognate to Japanese iki(ru), "live," and the second half is presumably the same as the mushi that means "bug" (in both Okinawa and mainland Japan). So it seems to literally mean "living bugs", "creepy-crawlies", "quicklin' beasties", something like that. In Japanese, though, it usually gets glossed as ikimono, "living things". Lame!
Related proverb: "Stay alive long enough and you might see jellyfish bones." "Where there's life, there's hope," in other words, although the Okinawan version is much more up-front and cheerful as comforting falsehoods go.