I know that there is plenty of advice on how much salt we should eat due to its supposed tendency to raise blood pressure. However is this accepted as being proven? And if so, is the magnitude of increase of significance. (I don't mean statistical significance, I mean medical significance.) Also, how could researchers investigate the effect of salt on blood pressure and eliminate the placebo effect? We can taste salt in our food. The subjects being given a high salt diet would know, and this itself might cause their measured blood pressure to be higher. The subjects with a low salt intake would be expecting low blood pressure.