By Len Maniace
First some fun facts on sodium in our diet:
* Experts estimate that Americans on average consume more than three times the sodium than was typical of prehistoric humans.
* Only about 5 percent of the sodium consumed by the average American is shaken on; almost all the rest comes in foods processed to tempt our taste buds.
* In Finland, highly salted foods contain a health warning.
For some four decades we’ve been advised to watch our sodium intake in the hope of reducing our chances of death from cardiovascular disease. A forum by the New York City Food Policy Center this morning looked at the underpinnings of that policy and asked how much evidence is needed before public officials issue health warnings.
No one called anyone a nanny statist or a shill for the salt lobby – and, yes, there is such a thing. That’s because the speakers were respected health experts who attempted to get to the truth of the issue rather than rack up debate points. The discussion won’t make it onto tabloid television, but the talk was instructive because it showed how public-health science works – or least is supposed to.
Dr. Thomas A. Farley, New York City Health Commissioner in the Bloomberg administration, made a compelling case that sodium in our diet poses a serious hazard. He pointed to studies showing that high-sodium diets are linked to high-blood pressure and that high-blood pressure is connected to cardiovascular disease and death. Still other studies have shown that people from societies that consume much less sodium see their blood pressure rise when they move to nations with high-salt diet. Meanwhile, decreases in cardiovascular disease have accompanied campaigns to reduce sodium intake in Japan, Finland and the United Kingdom.
Farley was quick to point out that such studies are not proof on their own, because many other factors can also be at play, but that they do buttress other studies.
Scientifically, the best way to determine the risk from sodium would be a massive project in which a study group is divided with one half eating a high-sodium diet and the other, one that’s low in sodium. Besides serious issues of whether the test subjects will stick to their diets, Farley said the study would not be ethical. “To take least 14,000 people and tell them, ‘No, you are are going to stay on a high-sodium diet for the next five years to see if your heart-disease rate gets really high.’ So, such a trial is never going to happen.”
Current guidelines call for the general population to limit sodium consumption to no more than 2,300 milligrams per day. Those in high risk groups – people with high-blood pressure, diabetes, kidney disease, blacks, and anyone over 51 – should keep daily consumption to no more than 1,500 mg.
Dr. Sandro Galea, a physician and epidemiologist at Columbia University’s Mailman School of Public Health, however, raised questions about the evidence. First, he said that while 60 percent of the studies show a connection between high sodium diets and cardiovascular disease, 40 percent failed to find the connection.
Unlike trumped-up television debates, however, Galea was quick to highlight the areas where he agreed with concern over dietary sodium. “There is no space between Dr. Farley and myself on salt reduction in particular subgroups, or the fact that salt consumption in particular subgroups leads to hypertension. There’s no debate over that, let’s not even waste time discussing it.”
Rather, he said, the question is whether reducing salt consumption in the overall population will reduce the death. Galea said he believed that since the evidence was not conclusive, public health science put its credibility at risk by taking too strong a stand. Furthermore, he said, there were significant and more definite hazards where the public-health community should weigh in, such as the need for adult motorcyclists to wear helmets, and guns.
Not necessarily an unreasonable position, though if one is picking ones’ battles, Galea’s prescription would run into a lobbying group with considerable more power than the salt industry – the National Rifle Association.