The evidence shows that the basic question asked in the Pimenta study is the wrong question. The right question is whether a recommendation to lower dietary sodium in the general population will improve public health, whatever the mechanisms involved.

The evidence is that lowering dietary sodium triggers many changes in the body (and different people respond differently). Some will lower BP, especially if they are consuming only deficient intakes of K, Mg, and Ca. Most will also respond to lower Na intakes by increasing insulin resistance, plasma renin activity, aldosterone production and sympathetic nervous system activity. It is the NET EFFECT of all these changes that results when salt intake is reduced and it is the net effect that represents the health outcome.

Lower salt diets in the general population have been associated with increases in cardiovascular mortality, incidence of myocardial infarction and all-cause mortality. These, unfortunately, have all been observational studies; the government has refused to fund a trial of the question of whether reducing dietary salt achieves better outcomes.

An Italian team, however, HAS reported a clinical trial of the health outcomes of low-Na diets (in late 2008 and earlier this year). Their subjects were patients treated for congestive heart failure, a group that has routinely been treated with low-Na dietary therapy. These researchers found that, contrary to all expectations, those receiving low Na diets died more quickly and were re-hospitalized more frequently.

So as interesting as are studies that show that massive salt loadings raise BP and drastic Na reduction cuts BP, with respect, we already knew that fact. We need a trial in healthy subjects as to whether using salt reduction can reduce or prevent heart attacks and extend life.

That question is the key, but a second question would need to be answered even if the data were to return conclusions opposite those of the observational studies showing no health benefit. That second question is: can the general public sustain salt reduction by choosing low-Na foods (whether through education or "stealth" removal of NaCl from the food supply) or is there an inherent and neurally-modulated "central regulation of sodium appetite" as some researchers have proposed -- where the brain unconsciously regulates desire to consume foods until the body's need for this essential nutrient is satisfied.

So many questions, too few answers. But it will help if we answer the right questions.