I read somewhere that eating a lot of salt will raise blood pressure, which will in turn damage brain tissue. This is because water molecules gather around salt ions, thus making it harder for the body to remove the excess water from the blood.
Is this true? How much salt is actually dangerous?
Good question. The answer really depends. There is a normal range of plasma sodium concentration that ranges from about 135 to 145 mM. You body has multiple endocrinologic and neurological mechanisms to closely regulate this concentration. So even if you went out and ate a ton of salty snacks, your body would still keep your plasma sodium concentration within this range. A salt concentration much lower or greater than this can start to cause problems depending on how fast it happens and how far from the normal value. Brain surgery patient are often given lots of extra salt to keep their brains "salty" as this protects from cerebral edema and counteracts salt wasting that often occurs with brain injury. However, the opposite or very high sodium concentrations are also not good. As you said, a diet high in salt can lead to high blood pressure and chronic high blood pressure can cause damage the small blood vessels in the brain and cause small strokes over time or very high blood pressure can cause larger bleeds. Usually we see this in patients with very high uncontrolled blood pressures in the 170-200s systolic range. I'm kind of pulling those numbers out of my memory and you would have to check the literature to verify.
