For something that’s so often mixed with anti-caking agents, salt takes a lot of lumps in the American imagination. Like fat, people tend to think of it as an unnecessary additive — something to be avoided by seeking out processed foods that are “free” of it. But also like fat, salt is an essential component of the human diet — one that has been transformed into unhealthy forms by the food industry.
Historically, though, salt was prized. Its reputation can be found in phrases like, “Worth one’s salt,” meaning, “Worth one’s pay,” since people were often paid in salt and the word itself is derived from the Latin salarium, or salary.
Those days are long over. Doctors and dietitians, along with the USDA dietary guidelines, recommend eating a diet low in sodium to prevent high blood pressure, risk of cardiovascular disease, and stroke; and doctors have been putting their patients on low-salt diets since the 1970s. But a new study, published in the May 4 issue of The Journal of the American Medical Association (JAMA), found that low-salt diets actually increase the risk of death from heart attack and stroke — and in fact don’t prevent high blood pressure.
The study’s findings inspired much criticism and controversy — as research that challenges conventional dietary wisdom often does. When The New York Times briefly reported on it, even the title conveyed the controversy: “Low-Salt Diet Ineffective, Study Finds. Disagreement Abounds.” The Times reports that the Centers for Disease Control and Prevention “felt so strongly that the study was flawed that they criticized it in an interview, something they normally do not do.” According to the Times, Peter Briss, a medical director at the Centers, said that the study was small, that its subjects were young, and that they had few cardiovascular events — making it hard to draw conclusions.
But most of all, Briss and others criticized the study because it challenges dietary dogma on sodium intake. These experts claim that a body of evidence establishes sodium consumption as a serious driver of cardiovascular disease. But if you take a careful look at the evidence, you’ll see that the case against sodium crumbles under the weight of its contradictions. Gary Taubes wrote about the controversy on the benefits of salt reduction more than 10 years ago in a piece for Science called “The (Political) Science of Salt.” He portrayed a clash between the desire for immediate and simple answers and the requirements of good science. “This is the conflict that fuels many of today’s public health controversies,” Taubes asserted.
The JAMA study published early this month is not the first to find that a low-salt diet may be detrimental. In 2006, data from the NHANES II study showed that death from heart disease and all causes rose with lower salt consumption. Published in the American Journal of Medicine, the report found:
Lower sodium has been associated with stimulation of the sympathetic nervous system, that, in turn, has been associated with adverse [cardiovascular disease] and mortality outcomes. Sodium restriction may also influence insulin resistance.
The insulin resistance association is compelling since so many Americans are exhibiting signs of insulin resistance, the precursor to diabetes. Michael Alderman, a blood-pressure researcher at Albert Einstein College of Medicine and editor of the American Journal of Hypertension, said in an email, “The problem with reducing sodium enough to change blood pressure [is that it] has other effects — including increasing insulin resistance, increasing sympathetic nerve activity, and activating the renin-angiotensin system and increasing aldosterone secretion. All bad things for the cardiovascular system.”
There are those who will argue that any study claiming that sodium is not as harmful as previously believed are connected to the salt lobby, but this is untrue. The most recent JAMA study has no such connection and many real-food advocates, myself included, believe that salt is an essential part of a healthy diet. Alderman was once an unpaid consultant for the Salt Institute but no longer is, according to the Times article.
There is also a strange psychological component to this debate as is often seen in the nutrition world: When a message has been hammered in and repeated millions of times over the course of decades, whether or not that message is actually true becomes irrelevant — and the people invested in presenting that message, whether for monetary gain or not, are especially resistant to any evidence that might be contrary. When asked about this phenomenon and the standard recommendations on salt, Alderman said, “They are based upon the hope that the blood pressure effect of lowering sodium would translate into a benefit in health. Opposition to these findings — which only adds to a substantial body of similar information — is that these folks have long held the faith that lowering sodium was a good idea. They have opposed randomized trials with the bogus argument that a randomized controlled trial would be too tough and expensive. Not so. They choose faith over science, but it’s not a theological issue.”