Salt isn't bad for you, really. In general, at least. When you eat something salty, the salt is absorbed very quickly into your bloodstream. But it's filtered out again almost as quickly. The trick is that water has to go with it. Your body tries to keep the concentration of salt in your bloodstream the same all the time. (The concentration is how much salt there is in a certain amount of fluid.) So if there's more salt, there has to be more water. And it's very difficult to filter the salt out without removing water, too. So if you're going to eat a lot of salt, it's very important that you drink plenty of water. Otherwise, your body will have to pull water out of your cells to even things out, which would dry your cells out.
So this means that as long as you drink enough water, you can eat as much salt as you want, right? Well, it depends. I said earlier that the salt (and water) are filtered out of your blood almost as quickly as they are absorbed into it. The key word here is the "almost" - before the salt (and water) can be filtered out, it does have to spend some time in your blood. This means that the total amount of blood is actually higher. And having more blood in the same sized blood vessels makes the blood pressure higher too. So for anyone who is at risk for problems having to do with high blood pressure, eating lots of salt can be a problem. However, the people who study this stuff have yet to figure out just how big the effect on blood pressure really is.
(published on 10/22/2007)