It’s clearly a sign. Vegetables are tying to kill us. :( apparently bamboo is deadly to humans and only pandas and lemurs (spelling) can eat it raw. It must be boiled for a period of time for human consumption.
Of cause they try to. It is normal evolutionary behavior of plants. And co-evolution of humans to being able to tolerate this toxins.
In fact, milk and wheat may have compounds, that are addictive.
I seem to remember a Bruce Sterling book(Islands in the Net?) where one of the characters avoided vegetables for this reason.