The World Health Organisation says we’re in the grip of a ‘crisis’ of non-infectious diseases – and salt is one of the main culprits.
That's because of its effect on blood pressure and hence cardiovascular diseases such as heart attacks and strokes. The only substance that gives the WHO greater cause for concern is deadly tobacco.
Most people eat much more salt than they need. While US dietary guidelines set an adequate intake of 3.75 grams a day, the average Westerner eats about 8 grams; in some parts of Asia, 12 is the norm.
Around three-quarters of the salt we eat is added to food before it even reaches our plates, not only in the obvious culprits like crisps and cured meat but also concealed in breakfast cereal, biscuits and crackers, cheese, yoghurts, cake, soup and sauces.
Even bread is surprisingly salty.
As well as prolonging shelf life, salt makes cheap ingredients taste better and masks bitter flavours that often result from industrial cooking. It can be injected into meat to make it hold more water, thus allowing water to be sold for the price of meat. It improves the appearance, texture and the smell of the final products.
And it makes you thirsty, boosting sales of drinks.
Our kidneys can excrete some excess salt but even so, people who consistently eat more than about half a gram a day – that is, practically all of us – build up excess sodium.
To keep fluid concentrations stable, our bodies retain extra water. As a result we’re all carrying round up to a litre and a half of fluid, weighing one and a half kilograms, more than we would if we were on our natural salt intake.
A consequence of this excess fluid is a rise in blood pressure – one of the main risk factors for cardiovascular disease. Even small increases raise your risk of having a stroke, and everything that lowers blood pressure reduces it.
For this reason, salt reduction has become one of the most important public health targets in the world.
Dietary guidelines vary, but generally recommend eating no more than five to six grams of salt a day. And these levels are far from ideal – they are merely what is considered realistic in a world awash with salt.
Try calculating your own salt intake and you’ll soon learn how hard it is to meet even this modest target.
Modern diets are not only laden with sodium but also depleted in potassium, so an effective way to boost the health benefits of salt reduction is to switch to high-potassium table salt or eat more high-potassium foods such as bananas, oranges and black beans.
However, if you have kidney disease, heart disease or diabetes, seek medical advice as an increase in potassium may be harmful.
One way to cut down on salt is to use spices as a substitute. Spices may even bring health benefits of their own. They are often rich in polyphenols, plant compounds thought to have antioxidant properties.
The best-known super-spice is turmeric. Its magic ingredient is curcumin, which has anti-inflammatory properties.
More than 120 trials have tested its effectiveness against conditions from Alzheimer’s disease to erectile dysfunction, and each month dozens of new scientific papers are published on its effects.
This Book Could Save Your Life: The Science of Living Longer Better by Graham Lawton and New Scientist, published by John Murray, £14.99 is out now
Six facts about salt you probably didn't know
1. The typical foods available to our hunter-gatherer ancestors would have been low in salt, so we have evolved a system for detecting it in our diet. This means one of our five types of taste bud is dedicated exclusively to salt – the only one tuned to a single chemical.
2. Until recently most humans ate no salt other than what was naturally in their food, amounting to less than half a gram a day.
3. Pure salt entered the human diet only around 5,000 years ago when the Chinese discovered it could be used to preserve food.
4. Unlike energy, our bodies cannot readily store salt and so we are experts at hanging on to it, largely through a recycling unit in the kidneys. It is possible to survive perfectly well on very little salt.
5. Our liking for salt appears to be learned. People living in traditional societies, such as the highlanders of Papua New Guinea, have no access to pure salt and find it repulsive, but if they move to the city they quickly get a taste for it.
6. Like an addictive drug, the more salt you eat the more you crave, as salt receptors on the tongue become desensitised by overuse.
This Book Could Save Your Life: The Science Of Living Longer Better by Graham Lawton and New Scientist is out now (published by John Murray, £14.99)
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