On the scale of problematicals, starving to death is much less preferable than eating something that might be somewhat unhealthful.
IF (repeat, IF) this worries you, look for older, heirloom varieties; if stored properly, they can not only be eaten, but also planted.
Then one day somebody had a mutant baby and that baby grew up able to eat the otherwise dangerous to eat wheat, barley and rye.
Eventually there were a lot of babies who could eat those dangerous plants, and they began to outnumber the original, non-mutated humans!
Now they imagine wheat, barley and rye are healthful and that the original model humans with all the correct genes are somehow DAMAGED.
We have the same situation with lactose intolerance. The original people did not drink milk after childhood because they could no longer digest it properly ~ unless they turned it into aged cheddar or yoghurt.
Then, there's rice ~ it was first domesticated in the Aleutian islands and brought South to East Asia where mutant people arose who could eat it EXCEPT 10% of Japanese cannot! The mechanism is similar to that which prevents West Asian folks from eating wheat, barley and rye although the allergic expression is different. They lose their skin to great welts, whereas with coeliac you just lose your guts!
Fortunately there's corn. There's tapioca. There's sorghum. There's ....... well, a wide variety of other nourishing and edible plants. That's why we still have the original models of humanity wandering about