Food safety regulation isn't about making me to eat my vegetables. It's about making sure my vegetables aren't contaminated in ways that I can't reasonably detect.

A producer who skimps on food safety can save costs, and the externality is people getting sick, through no fault of their own.

That is not what "unpriced externality" means.

And if your vegetables being "contaminated in ways that you can't reasonably detect" isn't a case of you not knowing what is good for you, I don't know what is.