It's nature's best flavour-enhancer and the mainstay of manufactured meals. So how come we're eating less of it without even noticing?

Like many chefs, and quite a few of the rest of us, Mark Greenaway is trying to cut down on salt. He seasons sparingly, only uses natural sea salt rather than processed table salt ("even for boiling potatoes"), and lives by the mantra that "as soon as you start tasting salt, you've added too much".

The chef patron of Restaurant Mark Greenaway in Edinburgh is also experimenting with alternatives, such as a dried Scottish seaweed called dulse. "It has a wonderful natural saltiness," he says, "but there are other flavour notes, too. It's not for everything – it's not a straight replacement for salt and you wouldn't use it on, say, a sirloin steak – but for fish dishes and some soups, it works really well."

But Greenaway won't give up on salt completely, as one or two more avant-garde chefs have vowed to do. He'll reduce it where he can, "but never to the detriment of a dish", and he'll use less of better quality salt. But ultimately, and like the rest of us, he believes that salt is too important to the flavour of food to ignore.

It's often said that salt enhances the flavour of other ingredients. Dr Gary Beauchamp, director of the Monell Chemical Senses Centre, a non-profit research institute based in Philadelphia, was one of the first scientists to understand why. First off, he says, salt makes food salty, but it also enhances the palatability of food in lots of other ways. "The clearest one is that the Na in salt (NaCl) is an excellent bitter blocker," he says. "So when salt is added to a bitter food such as a vegetable it inhibits the bitterness and as a consequence makes other pleasant flavours such as sweet more prominent. We also believe that it enhances flavour in other as yet unknown ways."

Greenaway adds: "Salt does enhance flavour and I wouldn't do without it altogether. Some people might experiment with spice mixes as a replacement but spice doesn't enhance flavour, it changes the direction of the flavour." Top chefs tend to agree. Raymond Blanc, railing last year against a proposed ban on salt in New York restaurants, insisted that "for some kinds of cooking, salt will always be essential. You need it. Not much of it, but you need it."

Those of us who always sprinkle salt on food after cooking or experience an addict's craving every time we pass a fish and chip shop, may not agree that less is always better. But whether we enjoy salt for its saltiness or for its more subtle favour-enhancing qualities, it seems like we're hardwired to sniff out salt as if our lives depended on it. Which, of course, they do. Amid all the talk of reducing our salt intakes, it's worth remembering just how fundamental our relationship with salt is. Sodium is an absolute requirement for life in a way that vitamin C isn't, which is why we crave crisps and not oranges. It makes our muscles move and our minds remember. Without it, our hearts would stop beating.

"Since salt is often rare in the environment and the body has no way to retain it, it appears that many species developed an innate liking for the taste – just as we also have an innate liking for sugar/sweet that signals necessary calories," says Dr Beauchamp. "And because the downside of excess consumption doesn't come until late in life, mainly after our reproductive years, there are no evolutionary pressures to avoid it."

It's pesky evolution again, and its total disregard for our health after we've passed the age of reproduction and child-rearing. Your flesh needs salt so it craves it, and has done for a very long time.

"Life is thought to have begun five billion years ago, in the seas and oceans," says Russell Keast, a former head chef and now Associate Professor of food and nutrition at Deakin University in Australia. "The transition from sea to land happened only 300 million years ago, and the successful transition from sea to land required bodily cells to be bathed in a salty solution."

Evolution is an agonisingly slow process, and we've had no time to adapt to salt's current ubiquity. In an exact correlation with our relationship to fat and sugar, we're suddenly surrounded by something that we evolved to think of as a rare and finite resource.

But there's a twist to this salty tale. We're eating less of it. As a nation, we still eat too much salt, which contributes to raised blood pressure and a higher risk of heart disease and stroke, but Professor Jack Winkler, director of the Nutrition Policy Unit at London Metropolitan University, calls the campaign to reduce salt "the most successful UK nutrition policy since the Second World War".

Most of our salt consumption comes from processed food, which is often pumped full of industrial grade salt. The Food Standards Agency (FSA) has persuaded food manufacturers – who for decades fed our craving with ever-saltier breakfast cereals, crisps, sauces, soups, pizzas and bread – to reduce the quantities they use.

It's perhaps indicative of our love of salt that you may not have heard of the FSA's salt-reduction strategy, or even been aware that it had one. Witness the howls of protest after the makers of HP Sauce recently trumpeted a lower-salt recipe and you'll realise why few food manufacturers have been shouting about the good news.

Or maybe it's just hard to trumpet slow, unspectacular progress. The campaign has worked because food companies were asked to agree small, incremental reductions, which might go unnoticed by consumers. On top of that, brands agreed to the reductions in tandem, so no producer could get competitive advantage by keeping salt levels high. The reductions are repeated every two years.

"Commitments were tracked and made public and progress was reported on regularly to hold companies to account," says Jacqui Webster, who led the FSA's salt-reduction strategy at the start and has since been headhunted by the Australian Government to repeat the trick there. "Not many public health campaigns are actually able to demonstrate a difference in such a short time. The FSA work led to a reduction in salt of about one gram in the first few years, which is estimated to be saving around 6,000 lives a year."

Large manufacturers such as Kellogg are on board. It agrees that incremental steps are the way forward. "In some products, such has Special K, we have been able to reduce the sodium level by 46 per cent – however, in other products it's a slower process and we need to continually reduce in (small) steps to take people's palates with us," says Kellogg's Louise Thompson Davies. "That's incredibly important because if you don't do it right, shoppers will simply turn to higher-salt alternatives, which isn't good news from a public-health point of view."

The data on the next four years of the strategy will be published in 2012 and will most likely show a further decline. The strategy is showing what chefs such as Greenaway instinctively know. People are prepared to accept less salty-tasting food, if the reduction is gradual and there's still enough salt to inhibit bitterness and enhance more pleasant flavours. Salt-free food would be terribly bland or bitter; reduced-salt food needn't be.

And it's not just that we're eating less salt. We're also consuming better salt. Over the last few years the popularity of unrefined sea salt has rocketed. That was initially driven by taste – now it's also being driven by health. Unrefined salt contains sodium and a wealth of trace elements such as potassium and magnesium, which help the body to metabolise sodium. Table salt contains sodium and anti-caking agents. A study last year by researchers at Wageningen University, in the Netherlands, found that eating salt with increased potassium could lower blood pressure to the same extent as cutting out four grams of salt a day, or half an average westerner's daily intake.

In other words, there's probably no need to give up your favourite seasoning if you use the good stuff sparingly and steer clear of processed foods as much as possible. Which is good news for lovers of good food. All the evidence suggests that we're too hardwired to love salt and its subtle effects to be happy with a salt-free diet.

A little of what you fancy: gourmet salts

Flake Salt

Sea salts are made by evaporating sea water. Flake salts – such as Maldon sea salt and Halen Mon – are delicate, pyramid-shaped crystals, adding a subtle hint of briny flavour to any dish.

Fleur de Sel

Harvested from the top of salt ponds using traditional Celtic methods, Fleur de Sel is considered the caviar of salts, with – it's said – hints of rose and violet. True Fleur de Sel has to come from the Guérande region of France.

Grey salt

Grey salt is moist and unrefined sea salt, which retains the light grey colour from the clay of the salt flats where it's harvested. It can be course or stone ground – the latter a perfect replacement for refined table salt.

Smoked sea salt

Smoked salt is taking the culinary world by storm, adding a unique flavour to anything from roasts to salads. Go for the salt that has been slow-smoked over wood fires and watch out for the stuff that has just been infused with bitter chemical flavouring.

Flavoured salts

Vanilla salt, truffle salt, celery salt, paprika salt – all are available and increasingly popular. Truffle salt is said to be particularly good on pasta, giving the flavour of truffles at a fraction of the price.