Savour the salt

Ignore the conventional wisdom. There is no evidence that salt, something we need to survive, is bad for us.

Take all those health warnings about table salt with a pinch of salt. The evidence that our current levels of consumption do more harm than good for human health has little weight, any which way you look at it.

The Japanese have one of the world’s highest levels of salt consumption and are also the most long-lived people on Earth, with the possible exception of Jews, whose kosher salt-laced foods rival those of the Japanese. In fact, the societies that consume the most salt tend to enjoy the longest life spans, and societal well-being throughout history has been tied to the availability of salt.

Salt is no mere food additive. It is fundamental to life, an indispensable regulator whose sodium ions keep our bodies’ chemicals in check and prevent our bodily systems from spinning out of control. Hippocrates in the 5th century BC realized that salt controlled our excretions and other basic functions, and developed salt treatments as an anti-inflammatory for respiratory diseases and for topical wounds. Ancient Jewish kosher laws relied on salt to protect the body from food-borne pathogens. The Latin word for health, salus, comes from sal, or salt, as does our salute and the French salutation, “salut.” Numerous societies venerated salt, often incorporating it into their traditions.

Because the body cannot manufacture its own salt, and because body functions are utterly dependent on salt, we humans must continually take in salt with our food to survive — some estimate our physiological need at 5 to 10 grams per day. Salts perform service to us in our blood, in our organs and in our cells, and although medicine ultimately knows little about salt’s complex role in the human body, we do know that when we become salt-deprived, our body fluids react by changing the body’s level of insulin, potassium and excretions. Numerous diseases are associated with salt deprivation.

Should we dismiss all the studies showing a link between excess salt consumption and human health? No, each represents a small piece in the giant jigsaw puzzle that is the enigma of the workings of the human body. Some studies indicate, for example, that salt intake is related to blood pressure and blood pressure is in turn related to various ailments. Some demographic sectors of society — in particular various African American subsets — tend to be salt-sensitive, making them subject to salt-related conditions that Caucasians are impervious to.

But none of the many studies into salt has justified the generalized leap that some make in assuming a harmful health effect — none has ever shown, for example, that salt consumption increases overall death rates, or death rates from cardiovascular diseases, or from heart attack or from any other cause.

On the other hand, studies do point to increased risk of heart attack and higher death rates among some individuals on low-salt diets.  As explained in Reducing dietary sodium: the case for caution, an article published earlier this year in JAMA, the Journal of the American Medical Association, only one controlled trial of low-salt diets has taken place and it demonstrated worse outcomes. Other studies are split, with most showing no health benefit of reducing dietary salt. Populations that may be especially vulnerable to low-salt diets include the elderly and the pregnant.

Lowering salt levels across the board when every individual responds differently to the salt in his systems, is foolhardy, explains the JAMA author, Dr. Michael Alderman, former president of the International Society of Hypertension and current editor-in-chief of the American Journal of Hypertension. “Multiple randomized clinical trials have established that reduction of sodium intake sufficient to lower blood pressure also increases sympathetic nerve activity, decreases insulin sensitivity, activates the renin angiotensin system, and stimulates aldosterone secretion.” The health effects of sodium reduction, he concludes, will only be beneficial if reducing our intake of sodium kills fewer people than it saves, something that no one can say with any confidence.

Rather than letting low-salt advocates run wild with their hunches and impose an unproven and potentially disastrous salt policy on the population at large, Dr. Alderman proposes that we first study who would benefit from, and who would be harmed by, a low-salt diet. “An alternate, more cautious approach, calls for rigorous, large-scale, population-based randomized clinical trials,” he states. “These trials will likely demand a commitment by thousands of individuals for several years but will result in greater precision and scientific credibility to help answer the question — and vastly smaller risk of human and material resources.”

Dr. Alderman is far from alone in fearing the consequences of forcing dietary changes on us. The late Dr. Lawrence M. Resnick, executive editor of the American Journal of Hypertension and a professor at Cornell Medical College, several years ago resigned from a government panel that he believed was cooking the books on low-salt science, whose conclusions he called “nonsense.” And last October, a University of California study published in the Clinical Journal of the American Society of Nephrology warned that the salt-restriction advocates were playing with fire while addressing a non-problem.

“To attempt to use public policy to abrogate human physiology would be futile and possibly harmful to human health,” the study states.

Humans have evolved highly complex systems to maintain our body salt levels within a certain range and we can no more give up our craving for salt than we can our craving for oxygen. When the body becomes salt-deprived, the authors explain, our body’s defence systems will kick in to protect us from harm. In the words of the authors, “The complexity and sophistication of the central control of sodium appetite offers compelling support for the proposition that vertebrates evolved a mechanism to assure that their physiologic needs for sodium are defended when dietary access to it is limited or when excessive amounts of sodium are lost under conditions of stress such as hemorrhage, sweating or diarrheal illness.”

Of particular alarm to the authors is the government’s recommended target for our sodium intake. Its current guidelines call for a maximum daily intake of 2,300 mg of sodium, the equivalent of one teaspoon of table salt, a level outside the normal human experience: 17% lower than the lowest level of worldwide sodium intake and 38% lower than the worldwide average sodium intake.

The author’s conclusion — the government targets are an unattainable and thus a financially wasteful goal because humans could not stand to have their sodium needs unmet. Another conclusion: To the extent governments succeed in depriving the body of the salt it needs, the human condition will worsen, particularly for those especially vulnerable to salt deprivation.

Lawrence Solomon
Financial Post
April 23, 2010

First in a two-part series, click here for part two.

Read the sources for this column.

Fluid and Electrolyte Balance

Salt and geographical mortality of gastric cancer and stroke in Japan.

Can Dietary Sodium Intake Be Modified by Public Policy?

Intersalt: an international study of electrolyte excretion and blood pressure. Results for 24 hour urinary sodium and potassium excretion

Reducing Dietary Sodium: The Case for Caution

Medium term effects of different dosage of diuretic, sodium, and fluid administration on neurohormonal and clinical outcome in patients with recently compensate   heart failure.

 

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