Measuring salt intake just once might make us think it's more or less harmful than it really is—using multiple measurements over time shows the risk could be very different, by as much as 85%.

If you measure salt intake in healthy adults using multiple urine tests over many years instead of just one, you might get a very different picture of how much salt people eat — and that can change what we think about how salt affects heart and kidney health over time.

People aged 30 to 54 who eat more salt over several years are 12% more likely to die from any cause for every extra 1,000 mg of salt per day—and eating very little salt doesn’t seem to help them live longer.

Eating more salt is linked to a higher risk of heart disease, and this seems to be true whether scientists measure salt intake from what people remember eating or from their urine tests.

For people who already have heart disease, eating just the right amount of salt — not too little and not too much — seems to be linked to the lowest chance of heart problems or dying from any cause. Too little or too much salt might actually be riskier.

If you have pre-hypertension, having more sodium than potassium in your urine might mean you’re more likely to die from any cause — even if you’re not eating a ton of salt. It’s not just how much salt you eat, but the balance between salt and potassium that might matter more for living longer.