Salt and hypertension: why is there still a debate?

More than a quarter of human populations now suffer from hypertension paralleling the marked increase in the dietary intake of salt during the recent several decades. Despite overwhelming experimental and epidemiological evidence, some still debate the relation between salt and hypertension. Pointing to some conflicting data in a few flawed studies, they argue that policy interventions to reduce the dietary intake of salt are premature and maybe unsafe without further studies. A brief review of data relating salt intake to hypertension, along with an overview of the history of the introduction of salt to human diet on an historic and evolutionary time scale, should help dispel doubts on the effectiveness and safety of low-salt diet. The recorded history confirms how rare and inaccessible salt has been until recent times. Like all other terrestrial life forms, humans evolved in a salt-free environment under intense evolutionary pressure for the selection of salt-conserving genes. Hypertension is a prototypical evolutionary maladaptation disorder of the modern man-a species exquisitely well adapted to low salt conditions suddenly confronted with salt excess. The World Health Organization and many governments have finally taken action to reduce dietary intake of salt, which already has started to reduce the burden of hypertension and the associated cardiovascular morbidity and mortality. This brief review is to broadly look at the evidence linking salt to hypertension from a historic and evolutionary perspective as well as touching upon some of the epidemiological and experimental data.