Genesis 9:3
NKJV - 3 Every moving thing that lives shall be food for you. I have given you all things, even as the green herbs.
For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
Not to rehash all the good answers, but allow me to add this simple explanation:
"It isn't what goes into our mouths, but what comes out of our mouths that defiles us,"
Beware of what you say.
It would seem that all the answers given missed the point of the original question, which was based on Genesis 9:3. This verse signals God transitioning mankind from a plant-based diet to an omnivorous diet. Since Scripture does not elucidate a reason, I will not speculate as to one. However, it would be good to see an answer that more directly addresses the original question.