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I grew up hearing the mantra

excess salt causes heart disease

I had a vague understanding that it caused deposits in the body or something. Now that I give it more thought - I come up with three vaguely plausible explanations for this:

  • kidneys have a fixed limit on how much sodium chloride they can filter from your bloodstream in a day
  • excess salt has an effect on oxidation/redux reactions or acid/base levels that means your body's chemical reactions aren't performing optimally
  • the excess ions mess with other reactions in the body

When I take the 'devils advocate' argument in my mind - my plausible arguments are:

  • how can salt cause deposits in the body? It would simply dissolve in the bloodstream
  • surely the body has sufficient chemical mechanism to flush out surplus sodium ions

Now the author here makes the following claim:

The entire field of research around salt is a colossal [stuffup], for a fairly simple reason: sweat is salty. If you sweat, due to exercise or high temperatures, you lose about 1g/L of sodium. So right off the bat, all the research that's trying to find a population-wide correct amount of sodium to eat is on a wrong track, because there's no such thing.

But it's even worse, because most of the research doesn't measure the amount of sodium people take in through food, it measures the amount of sodium they lose in urine. This isn't their intake, it's what's left after losses, so it's confounded by exercise.

And it's even worse than that, because while the actual studies indicate that there's no benefit from cutting salt intake, some high-status organizations once said there was, and are acting as though they can't take it back without losing face.

The overall result is that there are a bunch of people shouting "less salt!" and a bunch of people shouting "the same amount of salt!" and no one has any model of how much salt they actually need, so they occasionally end up deficient.

In addition, the article here claims:

...there are the epidemiologists whose research appears to point in the other direction. They track the connection between salt and deaths from heart attacks and strokes, and their studies indicate that while heavy salt eaters did die sooner, there is little evident danger from the average American’s intake.

My question is: What is the evidence that mammals are unable to process excess sodium chloride?

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