If he knows he is allergic to peanuts he just ask if there are peanuts in the milkshake. But I get your point.
The fact people don’t know what is best for them doesn’t mean a bureaucrat not even able to run a State properly knows better.
Second it is always subjective, maybe we do not value the same things, maybe I value risk and danger more than safety, maybe I value entertainment more than living a healthy life.
It is true the information is often incomplete but why the legislation should have the answer ? It would mean the information is within the hand of only one actor , so if the central power gets it wrong everybody gets it wrong and it makes outstandingly more damage. This has been the case many times in the US .