A pinch of reality about salt

Health Canada’s war on salt has detractors who say low-sodium diets can be hazardous to your health

A pinch of reality

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The Canadian government is in an all-out war on salt. According to Health Canada, about half of us are consuming more than double the recommended daily dose, and it plans to rectify that by altering the food supply. The problem, say critics, is that the response could do more harm than good. There’s no question high-salt diets can affect blood pressure, but several studies suggest this outcome, generally speaking, is dwarfed by other health benefits. In fact, the government’s position, critics charge, is based on out-of-date data, and ignores the most recent studies. Worse, Ottawa’s salt offensive could cause serious health concerns, including heart disease, low birth rates, kidney disease, or an early death. “[Canada’s] limits are not based on science,” explains Michael Alderman, a physician and epidemiologist at New York’s Albert Einstein College of Medicine and editor of the American Journal of Hypertension. “Folks that eat the least amount of salt have the worst outcomes. They die.”

The average Canadian consumes 3,400 mg—about 1½ teaspoons—of sodium every day. Health Canada advises an adult dosage of 1,500 mg a day, and a maximum of 2,300 mg. These are based on the “significant body of evidence linking high sodium intake to elevated blood pressure, which is the leading preventable risk factor for death worldwide,” reads the Health Canada website. “High blood pressure is the major cause of cardiovascular disease and a risk factor for stroke and kidney disease.” To achieve these targets, Health Canada is trying to raise consumer awareness on the dangers of salt, fund research, and change the food supply by lowering the amount of salt in everything from breads to cheeses and soups to sausages. If all goes according to plan, the average Canadian will be down to 2,300 mg of sodium a day by 2016.

The targets, says professor Mary L’Abbé, chair of the department of nutritional sciences at the University of Toronto, are based on a number of studies, including one from the Cochrane Collaboration from 2006 that conclusively linked salt to high blood pressure. L’Abbé is the former chair of the Sodium Working Group, which, before it disbanded last December, set Ottawa’s sodium-reduction strategy. “Reducing sodium by 1,700 mg per day would result in an average drop in blood pressure of two millimetres of mercury,” she explains (millimetres of mercury, or mmHg, is the measure used to describe the force of the blood against arteries. Optimal blood pressure is below 120/80 mmHg). Although 1,700 mg is still above the recommended daily level, even modest changes can affect the incidence of stroke and heart disease. “Obviously, the higher your initial sodium intake, the greater your benefit,” says L’Abbé. “But even with a 1,100-mg reduction, you still get blood pressure reductions.”

As salt and blood pressure are often linked, the connection is assumed to apply to everyone. The science is complex, but many scientists believe that a condition known as salt sensitivity explains why the blood pressure of some individuals rises with increased salt, but not others. For the majority, if you eat too much, “nothing happens, you just pee it out,” Alderman says. By contrast, the salt sensitive see a rise in their readings. The number of people who are salt sensitive isn’t known, but he estimates it’s between 25 per cent and 30 per cent of the population, and this minority skews the numbers.

There have been seven recent studies, three in the last few months, that link low sodium to mortality. For almost eight years, Jan Staessen, a professor of medicine at the University of Leuven in Belgium, studied 3,681 middle-aged Europeans. He found four per cent of people on low-salt diets of 2,500 mg sodium per day (significantly above the lower limit of 1,500 a day recommended by Health Canada) died of cardiovascular disease compared with one per cent who ate 6,000 mg a day. The reason, he says, could be from the blood-pressure-regulating renin-angiotensin system or other mechanisms that kick in when the body doesn’t get enough, which puts a strain on the heart.

In fact, many scientists believe high-salt diets are better for the body. They argue salt is the backbone of blood, and essential to cognition and movement, says David McCarron, professor with the department of nutrition at the University of California at Davis. It doesn’t just affect blood pressure, but a range of other functions, such as the workings of your nervous and circulatory systems. When you don’t get enough salt, the renin-angiotensin system releases extra hormones to reabsorb it from your urine and, according to a number of studies, these hormones cause insulin resistance that can lead to diabetes. Low-salt diets cause fatigue, explains Edward Stricker, a professor of neuroscience at the University of Pittsburgh, who has published extensively on salt. Pregnant women are advised to steer clear of low-salt diets, as it may result in babies with lower birth weights. Athletes who take ibuprofen for pain should also not subscribe to reduced-sodium diets, as these drugs tend to lower kidney circulation. And, according to a 2010 Dutch study, when old people consume low-salt diets, as often happens in nursing homes, it turns out they fall more often. “Older people’s kidneys are not very efficient at preserving the sodium that comes in,” explains McCarron. “So if you put old people on a low-sodium diet, you will create problems with their kidneys. They will become more sluggish and you will kill them.”

Health Canada’s current war isn’t the first anti-salt campaign. In the 1980s, in response to U.S.-government low-sodium warnings, Alberto Culver Co., now owned by the Unilever brand, introduced Mrs. Dash, a salt-free seasoning made of dried onion, garlic, orange rind and spices. By the 1990s, its popularity had reportedly faded. “The joke always was: ‘It’s pretty good, but would be better with just a pinch of salt,’ ” Tony Grenis, who used to work in product development for Mrs. Dash, told the Wall Street Journal. The Scottish government has led a low-salt campaign since 2004, and the latest results, published in June 2011 by the U.K.’s Food Standards Agency, show that it hasn’t made any difference—people continue to take in 3,600 mg of sodium per day. Other governments have fared similarly. In 18th-century France, the salt tax, the gabelle, was considered so unjust on a good perceived essential to eating and preserving food that a cottage industry grew up smuggling salt from low-tax regions to higher gabelle ones, explains Mark Kurlansky, author of Salt: A World History. “Salt is a basic need,” he says. “It’s viewed as a basic right. And historically when governments start messing with it, they get people really angry.”

Regardless of taxation, salt is universal: no matter the country, people eat similar amounts. There is some variation—the popular Mediterranean diet, which has been linked to lower incidences of heart disease, cancer, Parkinson’s and Alzheimer’s, has about 40 per cent more salt than what we currently eat in Canada, or more than three times what Health Canada recommends. Salt consumption though, is hard to alter: Americans have eaten exactly the same amount of salt for the past 50 years—3,400 to 3,600 mg a day. Some scientists now talk about the “wisdom of the body,” which regulates our salt consumption through appetite. “How many times can you roll the dice and keep coming up with that number?” asks McCarron. “Your intake of sodium is not set by the food industry. The brain is monitoring your sodium intake millisecond by millisecond. It’s telling the heart, the kidney, the appetite, you need a little more, you need a little less.”

Even if the Canadian government successfully pressures food producers to change, some suggest that Canadians will end up eating the same amount, explains Montreal-born Morton Satin, a molecular biologist and vice-president of science and research at the Salt Institute in Alexandria, Va. If we cut it out of processed food, people will simply sprinkle it back in. Meanwhile, salt producers aren’t concerned, because “there is more profit in table salt,” he adds. We haven’t got any studies on what might happen if Ottawa achieved its low-salt goals because no scientist “would want to put someone on 1,500 mg for a long period of time,” says Stricker. “It’s not healthy.” There aren’t any societies in the world that eat Ottawa’s 1,500 mg, except those who live in remote places where it’s unavailable, like the Amazon’s Yanomamo Indians. But they rarely survive past the age of 50.




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A pinch of reality about salt

  1. Maclean’s should do its homework — the primary source of this so-called “science” is paid by the Salt Institute, a salt industry organization dedicated to promoting higher consumption of its products. See NY Times article at http://www.nytimes.com/2006/09/13/business/13salt.html

    • You seem to know nothing of the Salt Institute beyond its name. Since you are so concerned about the science, for a change try reading it. I’ve read hundreds of sodium studies and the support for restricting sodium from the diet of healthy persons simply is not there. Don’t take my word for it: Read! Start with the DASH II. The conclusions are in direct contradiction of the actual results.

      • The DASH study showed “People with high blood pressure who ate the DASH diet at the lowest sodium level had an average systolic pressure reading 11.5 mm Hg lower than participants eating the control diet at the highest sodium level.” http://www.nhlbi.nih.gov/new/press/01-01-03.htm

  2. There is a difference between a low-salt diet and normalizing salt intake, ie., ingesting a normal amount of salt. Health Canada is advocating a return to normal levels of salt in the diet. The absurdly and dangerously high levels of salt intake that we observe today in people who consume largely processed and packaged foods and restaurant fare are wildly out of proportion to what would be consumed by someone who does his/her own cooking. By regulating industry to adhere to standards, even those who do not cook at home will be able to approach normal intakes of salt.

  3. Scientific American ~ Salt Wars Rage On:

    We called Scientific American advisory board member Marion Nestle, a professor of nutrition, food studies, and public health at New York University and the author of Food Politics ………..

    But if you do a clinical trial where you try to put large amounts of people on a low-salt diet, you just don’t see much difference between the people who say they eat a lot of salt and the people who say they don’t eat a lot of salt. In clinical trials the relationship doesn’t show up.

    Q: Why not?

    A: Two reasons: One that it’s impossible to put a population of people on a low-salt diet. Roughly 80 percent of the salt in the American food supply is in foods before people eat them—either in processed food or in restaurant food. Because so much salt is added to the food supply and because so many people eat out, it’s impossible to find a population of people who are eating a low-salt diet. They basically don’t exist.

    What’s the other issue? 

    Not everybody responds to a low-salt diet. There’s a proportion of people in the population who are sensitive to salt—if you lower their intake of salt, then their blood pressure goes down. There’s another (probably larger) percentage of the population who doesn’t respond. They are people who can eat as much salt as they want and still their blood pressure is low. 

    So you have this curious anomaly where whenever you do a clinical trial you get these complicated, difficult-to-interpret results that don’t show much of an effect. 

    Is it possible that this represents the limits of science? It’s black hole event horizons and salt intake?

    It may be. It very well may be. Or the science that we have is completely adequate and we already have the answer. I was once at a sodium meeting at which there were a bunch of statisticians. And I left with the statisticians and they said that “anyone who thinks that salt has anything to do with hypertension is delusional.” And that was on the basis on the clinical trials that show so little. And yet every single committee that has dealt with this question says, “We really need to lower the sodium in the food supply.”

    http://www.scientificamerican.com/article.cfm?id=the-salt-wars-rage-on-a-c

  4. The line “There’s no question high-salt diets can affect blood pressure” is absolutely false and should not have made it by the editors. The science is by no means supportive of this position. Shame on Macleans for not doing even the most fundamental homework!

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