Well, I didn't intend that as a conversation-ender, but it is true. This particular substance inhibits a particular function of certain gut flora that seems important. I think it's safe to call that significant.

What "particular function" is that? If it's "the part that influences neurological function", you don't have a complete argument. If you can't be specific about this, your argument falls apart, because almost everything we eat potentially "inhibits" (or accelerates) different areas of our gut flora.