Pass the Salt

In 1977, health experts declared a war on sodium. We sift through a mountain of salt science for a grain of truth.
Available on CBC Gem

Pass the Salt

Nature of Things

Some health experts say salt is dangerous — even deadly — while others say that it’s an essential nutrient, not a vice or bad habit that we must kick.

Salt, or sodium chloride, is often used for food preservation, preparation and flavouring. It’s needed to dry brine meat, blanch vegetables and can even alter the texture of a dish. Randi Rudner, an instructor at Stratford Chefs School in Stratford, Ont., says it would be impossible to run a quality restaurant without it.
Registered dietician Chelsea Cross says it’s vital for our heart, nerve and muscle function, as well as blood pressure regulation.

But there is a war on salt. It began in 1977, when a U.S. government nutrition report said that sugar, fat and salt were threats to public health. Although the evidence was shaky, salt got the blame for heart attacks, strokes and high blood pressure. The daily recommended limit was three grams of salt — about half a teaspoon.

Doctors have long accepted the connection between sodium and cardiovascular disease. In Pass the Salt, Dr. Peter Lin explains that a high-salt diet can increase blood pressure, but not for everyone. Only one in every three or four people are “salt sensitive,” adds professor Matthew Bailey, a kidney specialist from Edinburgh. Still, both experts think that we consume far more than we need.

Meanwhile, when Dr. Clyde Yancy, a cardiologist and former president of the American Heart Association, reviewed the latest sodium studies, he was shocked to find “no evidence at all of any benefit of any salt restriction.” He believes that, until there is more evidence pertaining to people of different backgrounds, sexes and body types, sweeping sodium restrictions might do more harm than good.

Could we go too low? Yes, according to professor Andrew Mente from the Population Health Research Institute in Hamilton. He led an international study that followed 94,000 people and monitored cardiovascular health and salt intake for an average of eight years. His team saw no links between salt and major cardiovascular events, except where average consumption went higher than five grams a day, as is common in China. But they did observe that going too low can trigger harmful hormonal responses in the body. As with other essential nutrients, he says, there’s a “sweet spot” when it comes to salt consumption.

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There’s a theory that we have a deep desire for salt because we evolved from creatures that swam in it. Now that we live on land, we carry an “internal sea” within us, says Bailey. But while our connection to salt may be ancient, there’s still so much to discover.

In 2009, a controlled long-term study of salt intake became possible during a multi-year simulated Mars space mission in Russia. German scientist Jens Marc Titze controlled the diets of the crew and monitored the precise amount of sodium they ingested and excreted. He and his team discovered that the long-held belief that all the salt we eat today is peed out tomorrow was completely wrong. Instead, the subjects’ bodies appeared to store salt. Now, Titze is running studies in Singapore with MRI scanners adapted to detect salt deposits in the body. He wants to find out where and why it’s being stored. Is it a benefit, a danger or both?

Nutritional science is still in its infancy. But as new pronouncements about dietary risks and benefits emerge every day, we need to remember to take them with a grain of salt.


Stream Now on CBC Gem

Pass the Salt

Nature of Things