The single most harmful substance in food?

Salt: so good, but so bad?

Salt: so good, but so bad?

Salt rocks.

It makes everything taste delicious.

It has also been called "the single most harmful substance in the food supply".

A new paper by Harvard attributes excess salt consumption to 1.65 million deaths annually worldwide.

While it was a "herculean effort" to collate the data from 66 countries, its findings have limitations.

"Our modelling cannot prove that sodium restriction reduces cardiovascular mortality," the paper's authors acknowledge in The New England Journal of Medicine (NEJM).

Limitations aside, there is no doubt we consume too much salt.

The average Australian eats nearly nine times the amount of salt humans need.

Jerril Rechter, VicHealth CEO, says a five-year study into more than 120 illness-prevention measures named salt reduction as one of the most effective to save lives in years to come.

“Salt is linked to strokes, heart disease, high blood pressure, gastric ulcers, stomach cancer and more than 20 other health problems,” Ms Rechter said.

So it would seem we simply need to pass on the salt, right?

Well, not necessarily. We need salt to survive.

A certain amount is needed for our body cells to function.

There is the equivalent of about seven tablespoons of table salt in a 50-kilogram person and it needs to be replenished as we pee and sweat it out each day.

But, there is a Goldilocks principle with salt.

Too little or too much and we are in trouble.

And exactly how much is just right is arguable.

"In the most general terms, getting less sodium [the problematic component of salt] in the diet lowers blood pressure," says the Harvard Medical school. "But how sodium reduction affects an individual depends on his or her genes, age, and medical conditions."

New studies, including the Harvard one, have attempted to detangle the complex salt-health relationship.

A second study, also published in NEJM, found those who consumed about half to one teaspoon of salt a day had "a lower risk of death and cardiovascular events than was either a higher or lower estimated level of intake".

Interestingly, a diet rich in potassium (found in beans, bananas, dark leafy greens and even potatoes) seemed to counter the harmful effects of salt.

A third study, which did not find a clear link between salt intake and blood pressure, found similar effects with potassium. http://www.nejm.org/doi/full/10.1056/NEJMoa1311989

The authors suggested that instead of an aggressive campaign for the public to reduce salt intake, recommending a potassium-rich diet might have greater health benefits.

"Taken together, these three articles highlight the need to collect high-quality evidence on both the risks and benefits of low-sodium diets," wrote University of Alabama vascular specialist Dr Suzanne Oparil in an op-ed in the NEJM.

So while the experts work on the high-quality evidence, where does that leave the rest of us?

Spending a little less time with the shaker still, it seems.

"We need to reduce our salt intake by 30 per cent if we’re to reduce our risk of heart disease, Australia’s number one killer," says Dr Robert Grenfell, cardiovascular health director, National Heart Foundation of Australia.

"Previous research has shown that by reducing our intake of sodium from processed foods by just 15 per cent over 10 years could stop 5800 heart attacks and 4900 strokes a year ...

"Most of us are trying to do the right thing by not adding salt to cooking or at the table but we’re still eating much more than we realise. Three-quarters of the salt we consume every day is hidden in the food we eat. Things like bread, canned food, breakfast cereals and pasta sauces."

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