This was interesting, in the NY Times science blog:
Dr. McCarron and his colleagues analyzed surveys from 33 countries around the world and reported that, despite wide differences in diet and culture, people generally consumed about the same amount of salt. … The results were so similar in so many places that Dr. McCarron hypothesized that networks in the brain regulate sodium appetite so that people consume a set daily level of salt.
The rest of the article is about efforts to regulate salt in foods. What if that finding were correct? Imagine trying to set up a regulatory environment to achieve “safe” salt levels if there was a neurological trigger in the brain to get a different amount. When we prohibit alcohol and drugs, it doesn’t work, but at least it fails differently for different people.