How much salt people should eat continues to be a murky issue. A paper in the February 2017 issue of the American Journal of Kidney Diseases examines the issue of salt (actually sodium) intake on the prevention of cardiovascular disease in patients with chronic kidney diseases (CKD) stages 2-4. It is a commentary on an earlier paper published in the Journal of the American Medical Association. Both articles are below. The AJKD paper suggests that sodium intake should be reduced in patients with CKD if it exceeds 3.3 g/day.
The first comment that should be made is that this recommendation is based on no data examining the effect of sodium reduction in these patients. The recommendation is entirely based on association and inference. High sodium intake is associated with hypertension and increased cardiovascular disease (CVD). Thus, the logical inference is that lowering said intake should prove beneficial. This is a reasonable inference, but one that lacks controlled observational evidence that the expected benefit occurs.
A little background is needed here. Hypertension is the most important cause of CVD. Hypertension can be broken into three general classes. 1) Volume dependent; 2) Vasoconstrictor induced; 3) A mix of the first two. Volume dependent hypertension occurs when for whatever reason the kidney retains salt until a new steady state is reached allowing all salt to be then be excreted but at the price of hypertension. If a patient has this form of hypertension he will benefit from salt restriction. If there is no volume component there will be no benefit from salt restriction. Patients with CKD typically have hypertension that is almost always secondary to salt retention and volume expansion. Thus, it is reasonable to assume that salt restriction will have a beneficial effect on CVD induced by hypertension.
If a subject with or without CKD does not have hypertension it is equally reasonable to conclude that he will not benefit from salt restriction. Reasonable assumptions usually prove true, but not always. That is why a controlled study examining the outcome of salt restriction on subjects with and without hypertension and on patients with CKD is needed to be sure of the benefit of salt restriction. Therefore, it seems wide of the mark to recommend that the entire normotensive population restrict salt as in current advice of the CDC and other interested organizations. The advice to patients with hypertension and CKD to restrict salt, though unproven, seems more likely to be supported by future research.
So if your blood pressure is normal and you are healthy, feel free to pass the salt shaker or more appropriately to keep it for yourself.