Should there be restrictions on the amount of sodium in processed and restaurant foods? Many public health advocates think so. They argue that people consume excessive amounts of sodium without even knowing it and mandatory restrictions would reduce the number of heart attacks, strokes, and even deaths that result from all that salty food.

But does the available research justify a population-wide restriction on sodium in food? Not quite, says Michael H. Alderman from the Department of Epidemiology and Population Health at Albert Einstein College of Medicine.

In a new editorial in the Journal of the American Medical Association, Alderman argues that the case for sodium restrictions isn't scientifically sound and caution may be the best route until more and better evidence proves otherwise.

The editorial points out, for example,  that no clinical trials actually link sodium intake to increased mortality in people who are otherwise healthy. All the trials conducted so far involved only heart failure patients and even those results don't conclusively demonstrate that sodium reduction is always beneficial. Without any data on how sodium reduction would affect the general population, these clinical trials have zero relevance to public health policy.

And with no clinical research examining the issue, most evidence supporting population-wide sodium restrictions comes from observational studies. The problem, according to the JAMA editorial, is that studies of this sort rarely justify public health recommendations. In the case of sodium consumption at least 13 have been conducted and the results are conflicting. 

"...[G]iven different populations, different diets and sodium intakes, different methods and conflicting results, more than 1 explanatory hypothesis has emerged. Neither more observational studies nor further debate over the available studies is likely to resolve this public health controversy," writes Alderman.

"The key point, however, is not which hypothesis best fits the observed data. The real issue relates to the inherent limitations of observational studies. These investigations describe the course persons who follow a chosen diet might have but provide no information about what might happen if that diet were altered. That requires a randomized clinical trial."

While advocates of mandatory sodium restrictions are confident that the benefits outweigh the costs, with significant limitations on the available research, Alderman suggests that caution may be the best route forward.

Actually finding out how such a policy would affect the majority of the population before enacting it may be a good place to start. 

Citation: Michael H. Alderman, 'Reducing Dietary Sodium: The Case for Caution', JAMA, February 2010, 303(5), 448-449