In the interest of the advocatus diaboli, I'll point out that the market frequently does nothing at all to restaurants that sell poisoned food. I'm not saying regulation does much more, but in a few specific (recent) instances, regulation has done much more than the market has. In the mid 90s, an e-coli outbreak at the West Coast fast food chain Jack in the Box sickened 700 people in 4 states, sending 100 of them to the hospital and killing 4. Jack in the Box was never going to self-correct because that would be an admission of liability, so had the Washington State Dept of Health not interfered, its likely many more people would have gotten ill.
Then, of course, there's McDonald's-owned Chiptole, which has made more people sick than coronavirus over the years with everything from E. coli and salmonella to whatever the hell C. perfringens is. They even tried to cover it up on at least one occasion. It got so bad in 2018 that the CDC had to step in. Obviously the market has no corrective effect on Chipotle's chronic propensity for purveying food poisoning as their stock is right as rain; otherwise McDonalds would have dropped them from the portfolio like they've done many other chains (Boston Market, anyone?).
The economic impact of this on either restaurant chain was nil, neither in the short nor long term, because, surprise, surprise--markets are imperfect. Again, regulation isn't perfect either, but in situations where the market is predisposed to act like a hungry tiger, I'd rather have the cage of the government around me for protection than not.
Of course, if you want to see what a TOTALLY unregulated food supply chain looks like, you can take a look at Sinclair's The Jungle. Just make sure you don't read it while eating...