Scientists have scoured the world and found that societies with the most salt in their diets tend to have the most high blood pressure. Some studies did come along later that blurred the link a little, but did show that older people tended to get the blood pressure problems in response to salt more so than younger people.
Scientists have to be careful here because it isn’t ethical to put people on high-salt diets to see what happens, but the famed DASH study (Dietary Approaches to Stop Hypertension) showed that a lower salt diet significantly reduced hypertension and even reduced BP in the control groups who did not have high blood pressure.
As you can imagine, the salt industry was all over this one! Nevertheless, the American Medical Association is after the FDA to cut in half the amount of sodium allowed in processed foods. This has yet to be done, so it’s up to us to control our own salt.
It's important to rein in high blood pressure, because blood jamming into the little tubes in the kidneys can cause kidney damage. High blood pressure can also damage blood vessels, eyes, and cause heart trouble or strokes.
Almost every food contains salt.