If the restaurant relies on government regulation to ban foods that are significantly carcinogenic or harmful. The restaurant has no way of otherwise making that determination. If you believe you are experiencing health problems due to eating a specific food you might be able to sue the company providing the product but probably not the restaurant.

No producer of any food has or would say that. No reliable scientist or doctor would attest to such a statement. They don't even say that about tobacco.

I received a notice from a local food company that the product they were serving has been proven to cause cancer.

NO, that statement IS NOT TRUE.

Whoever sent that letter is trying to scam you.

No law protects you.  

This is an attempt to get you to avoid suing them in case someone gets cancer from the product sold by that food company.  You certainly have the right to sue.

That's bizarre. Consumer rights come to mind.

Of course they're liable for the food you ate BEFORE you got the warning.

I got a warning from a restaurant which picked up my name/address from my credit card.  Yes, something on the menu had a recall, the restaurant didn't realize it, it was contaminated.  I don't recall cancer.  I believe it was shredded metal.