THE human tongue is hooked on salt, to the extent that it seems to savour the very word.
The term salary derives from the Latin word for salt, while to this day someone valued by others is considered worth their salt. Someone of lower status is “below the salt”, a throwback to feudal days when the salt shaker’s costly contents were reserved for the lord and his retainers.
For thousands of years, salt has helped humans survive. Its ability to protect food, especially meat, from spoilage meant that, up until the 20th century, people with salted food survived the leaner months. Today, in the era of refrigeration and canning, salt isn’t saving lives. Instead, it’s claiming them.
Sodium, which makes up about 40 per cent by weight of table salt, or sodium chloride, is an essential nutrient. But at only slightly elevated levels it starts to raise blood pressure, in turn damaging arteries and making them prone to accumulating the fatty plaque deposits that trigger heart attacks.
High blood pressure also increases the chance of stroke, which can be caused by the same type of blockage behind heart attacks, when it’s known as ischaemic stroke, or by blood vessel rupture, called haemorrhagic stroke.
The toll is enormous. Almost 23,000 Australians died of coronary heart disease in 2006 — about 50 per cent of all cardiovascular deaths — while almost 3200 died of stroke.
Despite the clear links of these conditions to salt, it remains present in our food at levels that are proving lethal. Salt is everywhere — in cheese and processed meats, soups and sauces — and can be particularly high in foods few people regard as particularly salty, such as cereals and bread.
“Human beings evolved on a diet that had about 1g to 2g of salt a day,” says Bruce Neal, senior director at the George Institute for Global Health in Sydney and chairman of the Australian Division of World Action on Salt and Health (AWASH).
“In the world now, there’s almost no country that eats just 1g to 2g a day . . . nowadays, most societies will be eating five to 10 times that.
“In Australia, we eat 8g to 10g a day; in parts of rural China, it’s 15g a day because they preserve a lot of things like vegetables in brine.”
Only about 15 per cent of the salt we consume is added deliberately to food in home cooking. Another 10 per cent is naturally occurring in the food; the vast majority, about 75 per cent, comes hidden in processed foods and takeaways.
Surveys show that 99 breakfast cereals tested contained up to 1063mg of sodium in just 100g of product, more than the entire recommended daily intake for a three-year-old and more than half the daily limit for a 16-year-old.
Even white bread contains more than 600mg per 100g, while processed meats can pack in more than 2000mg. As a result, everyone from babies to adults is consuming 50 per cent to 70 per cent more than the recommended upper limit and up to 10 times the amount they need.
Salt remains in the diet because people like its tangy taste or believe it brings out other flavours. The public’s palate has adjusted to the taste of salt so completely, foods without it are often rejected as bland. It is also used as camouflage for inferior produce.
“A lot of sausages are made of such low-quality product that if you didn’t have the very high concentrations [of salt] that you do — many sausages are as salty as seawater — you simply wouldn’t be able to eat them,” Neal says.
This week a landmark report funded by the National Health and Medical Research Council recommended mandatory caps to limit salt levels in three food groups — bread, cereals and margarine — as a cheap and effective way of slashing the number of strokes and heart attacks suffered by Australians each year.
The Assessing Cost-Effectiveness in Prevention report, conducted across five years by experts from Deakin University and the University of Queensland, ranked the benefits that could be achieved from 123 possible prevention schemes and found limiting salt in just these three foods was “another cheap intervention with considerable health gains and cost savings from avoided cardiovascular disease events”.
The report found the salt caps would also mean fewer people would need to take preventive drug treatment, a significant point given that cardiovascular drugs cost taxpayers almost $2 billion in 2008-09.
Experts such as Neal have been seeking to sound the warning bells about the dangers of salt more loudly. AWASH wants to encourage Australians to reduce their salt intakes to 6g a day, but Neal admits this is an arbitrary limit that reflects what may be practical to achieve, not what is safe.
“In Australia, say we eat 8g a day instead of 2g; that 6g extra will push up each person’s systolic blood pressure by half a millimetre of mercury each year,” Neal says. “That might sound tiny, but people are doing this for 50 to 60 years. It translates to having 20mm of higher blood pressure; it has a compounding effect throughout your life, slightly increasing your risk of stroke each time.”
A healthy 17-year-old may have blood pressure expressed as 110 millimetres of mercury (mmHg) over 70, where the first figure represents the systolic pressure during a heartbeat and the latter the diastolic pressure between beats.
On a healthy low-salt diet yielding the 1g to 2g a day, humans are designed for, this pressure would barely change throughout life, assuming the person also exercised.
The official threshold for high blood pressure, or hypertension, in Australia is 140/90. But as Neal says, there is nothing magic that happens at this particular point.
“People generally think that if you haven’t got high blood pressure, then you don’t need to worry,” he says. “But every millimetre higher you go slightly increases your risk.”
What this means is that the large numbers of people whose systolic blood pressure is about 130mmHg instead of 110 are at greater risk of a heart attack or stroke.
“The risk isn’t as big [as for people with hypertension], but there are many, many more of them,” Neal says.
“When you do the maths, you find blood pressure causes as many strokes and heart attacks in people without hypertension, as it does in people with hypertension. That’s not widely understood.”
Present practice often involves doctors measuring patients’ blood pressure and, if they qualify as having hypertension, advising them on how to eat more healthily or offering them drugs that are supposed to alleviate the condition.
The problem is, this approach is expensive — it costs an estimated $1bn a year in drugs and nurses’ and doctors’ time — and is not particularly effective.
“What this means is that the clinical hypertension program is only addressing a tiny fraction of all the blood-pressure-related disease, probably about 10 per cent,” Neal says.
Instead, reducing the salt content of foods — particularly cereals and breads, eaten in large amounts — would have far-reaching consequences.
“You have just to change the practices of a few big corporations. If you can do that, you can potentially change the amount of salt consumed by a very large proportion of the population.”
Will we miss the tang? Neal agrees low-salt baked beans taste “completely different”, and confesses he eats out less than he used to because he finds the food — even in fine restaurants — too salty.
“People’s palates are adjusted to consume too much salt,” he says.
“If you take salt out of the products, you will begin to taste other things; but if it’s a quality product, that’s good.”
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