Pass the salt: The myth of the low-salt diet

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Pass the salt. Eat a pickle! Add more anchovies to your salad! According to a new book by James DiNicolantonio, you can freely consume salt without worrying about your blood pressure and heart. In fact, too little salt can endanger your health.

Like Gary Taubes’ book, “The Case Against Sugar”, pharmacologist and cardiovascular researcher James DiNicolantonio shakes up a nutritional hornet’s nest with his new book, The Salt Fix: Why the Experts Got it All Wrong — and How Eating More Might Save Your Life. DiNicolantonio’s argument is simple: There is no credible evidence that a salt-restricted diet lowers blood pressure in the vast majority of people, nor does it lead to heart disease or stroke. In fact, he argues, salt restriction is harmful and seems to predispose us to such conditions as insulin resistance, Type 2 diabetes, elevated cholesterol and triglycerides, abnormal workloads on the heart, and kidney disease. Finally, DiNicolantonio reminds us that salt is the wrong little white crystal to blame for chronic illness. The real culprit is sugar.

Readers may find “The Salt Fix” rather shocking. We live in a salt conscious culture. During most of my adult life, I have believed that salt was bad for me. Fifty percent of Americans are currently monitoring or attempting to reduce their sodium intake and 25 percent are being told by a health professional to curb their sodium consumption. Avoiding salt is one of the Health Commandments. But as DiNicolantonio takes readers through the history of the scientific debates about salt — what he calls the Salt Wars — you can only be impressed by the weakness of the evidence in support of the original calls in the 1950s and ’60s for salt-restriction. Sample sizes were small, evidence misstated and there were no randomized controlled studies, the gold standard for medical research.

In 1977, the staff of Senator George McGovern’s Select Committee on Nutrition and Health Needs issued a report called “Dietary Goals for the United States,” that for the first time, advocated a dietary salt “goal” — specifically, less than 3 grams a day. As DiNicolantonio shows, poor science became bold public policy. Subsequent reports reiterated this warning, as did the National Academy of Sciences and various other scientific and public policy bodies. Time Magazine covers screamed “Killer Salt,” and so-called saltaholics were shamed at dinner tables all across the country.

Public health authorities were under pressure to deal with an epidemic of cardiovascular disease. In post-World War II America, the alarming rise of heart disease was becoming increasingly evident. In 1950 one out of every three men in the United States developed cardiovascular disease before reaching age 60. At the height of its prevalence in the late 1960s, cardiovascular disease was twice as common as cancer, and it was seen in all developed countries. It had become the leading cause of death.

The search was on for lifestyle factors contributing to heart disease. Public health authorities and researchers had made headway into the cure of other diseases (such as cholera) by examining environmental factors. Why not heart disease? Their reasoning made a certain sense. Most people eventually succumbed to what was then considered to be degenerative diseases, including stroke and cardiovascular disease. But the hope was that the onset of these diseases, while not staved off permanently, might at least have been delayed via a preventive approach. If such an approach could be developed, physicians and public health officials would adopt it and it would have a widespread impact. The key was to develop a protocol in which certain factors, like diet, could be modified. The public health message went from “lower your blood pressure” to “lower your risk of high blood pressure.” Salt was a convenient enemy. Rats fed a high-salt diet were seen to have elevations in blood pressure and researchers knew that hypertension was a primary risk factor in the etiology of heart attacks and strokes. In fact, one participant in these proceedings noted that salt was an “easier target” than saturated fats or sugar. Sugar, in particular, has been given a free pass until quite recently.

The problem for the salt-skeptics was that the data were ambiguous at best and, at worst, failed to show any significant relationship at all between salt intake, blood pressure and heart disease. When such a relationship was found at all, it was tiny — perhaps, at the most, a one point increase in a subject’s systolic or diastolic pressure. DiNicolantonio argues that most people, in fact, are not sensitive to salt intake at all. Drawing on his substantial knowledge of pathophysiology, he points out that for those of us with normal blood pressure, our kidneys are an incredibly powerful factory that efficiently excretes salt when levels rise above very tightly regulated upper limits (normal kidneys can filter the equivalent of over 1 teaspoon of salt every five minutes). When salt is restricted, on the other hand, our body regards this situation as life-threatening and initiates a cascade of hormonal and metabolic rescue maneuvers that, themselves, have negative side effects, including increases in heart rate and elevated serum levels of insulin, cholesterol, and triglycerides.

In the latter half of the 20th century, the advent of refrigeration replaced pickling, brining and curing as the primary mode of food preservation. This change lowered the average salt intake of Americans during the same period that heart disease and other chronic illnesses were on the rise. Salt, therefore, couldn’t be the cause.

DiNicolantonio doesn’t really offer an overarching explanation of why weak science came to be enshrined in our culture and in public policy. In contrast, the scientific and political denial of the overwhelming body of research showing the serious health hazards of refined sugar and high-fructose corn syrup can easily be attributed to the economic and political self-interest of the sugar industry. But there isn’t a “low-salt lobby” behind the sloppy science and rigid guidelines involving salt restriction. In the case of salt, the cause appears to be the interplay of highly competitive forces within the medical and public health establishments. Researchers doubled down on their own research, however effectively it was critiqued, and public health and policy authorities were unable to admit that their recommendations might have been wrong all along.

While the anti-salt forces have by and large won the day when it comes to “official” dietary guidelines, the scientific debate has been ferocious and “The Salt Fix” provides readers with a smart and interesting account of it. Science writer Gary Taubes once described it this way: “The controversy over the benefits, if any, of salt reduction now constitutes one of the longest running, most vitriolic and surreal disputes in all of medicine.”

DiNicolantonio takes a commonsense approach to the role salt plays in health and illness. Above all, salt ensures that we have enough blood volume to sustain life. It also makes food taste great. Our bodies have a natural thermostat that insures we get enough salt if we simply honor our natural salt cravings. This thermostat signals the brain to seek more salt when we need it and to stop when we have enough. All of this happens automatically, provided, that is, that we don’t screw things up by artificially restricting our salt intake. Sugar cravings, on the other hand, don’t arise from physiological need, except in rare cases when there is significant low blood sugar. Salt intake is a negative feedback system in which the body, at some point, tells itself to reduce intake (salt taste receptors actually switch from providing positive to negative sensations), while sugar is a positive feedback system in which the more sugar you eat, the more you crave it and therefore keep eating.

Sugar causes heart disease. Salt does not. So the next time you crave salt, indulge. You’ll be doing your body a favor.