Salt is one of those dangerously tasty substances. We add the magical crystals of sodium chloride to almost everything that we cook or bake, and according to many public health experts, we add too much.
They want us to cut back, to lower our risk of heart attacks or strokes.
Yet when you really start looking for ways to do this, you run into a paradox and a scientific puzzle.
First, the paradox. Too much salt may kill us, but our bodies need some of it to survive.
"If you don't keep up your sodium level in your body, you will die," explains Paul Breslin, a researcher at the Monell Center, a research institute in downtown Philadelphia devoted to the senses of taste and smell. (Breslin also teaches at Rutgers University.)
At the same time, Breslin continues, "there's no question that people who have high salt intakes are at risk for a heart attack and stroke and death, and that lowering their salt intake will save lives. In Finland, when they lowered the salt intake, stroke and heart attack rates went way down, and mortality went way down."
There are skeptics who discount the relevance of the Finnish example. The average person in Finland, at that time, was eating a lot more salt than Americans typically do. The anti-salt campaign brought that level down to around the global average. The skeptics say, for most of us, that average level of salt consumption may be just fine.
But both the World Health Organization and the U.S. Centers for Disease Control and Prevention are calling on people around the world to cut salt consumption even more. The average American, they say, should cut their intake of salt by a third.
This won't be easy, because people like salt. It makes many foods taste better.
This is where we get to salt's mystery. Scientists aren't exactly sure how much of our taste for salt is nature, and how much is nurture.
On the one hand, Breslin says, a massive international study of salt consumption around the world, conducted in the 1980s, suggests maybe we're born with it. "All across the planet, with a few exceptions, most people consume more or less the same amount of sodium," Breslin says.
The exception is people who can't easily get salt, such as isolated tribes in Amazonia. Everywhere else — from small villages in China to Chicago, people consume similar amounts — much more than our bodies need.
If humanity's taste for salt preference really is so universal, Breslin says, it's going to be really hard for any government to convince people to use less of it.
On the other hand, there's also some evidence that our preferences do shift, based on what's around us.
Gary Beauchamp, director of the Monell Center, says the first evidence for this came from stories told by doctors who ordered patients with high blood pressure to switch to a low-sodium diet. Their patients reported that "it was awful at first, but after a while, it wasn't so bad," Beauchamp says. Their taste sensors seemed to adapt, a little bit the way our eyes adapt to a dark room.
In fact, Beauchamp says, after they did that for a while, "when they went back to their normal food, it was too salty."
Beauchamp decided to carry out a more carefully monitored experiment to study this. He put people on a controlled, low-sodium diet, and they did adapt. "In about four to eight weeks, the amount of salt that they found optimal in soup or crackers declined by 40 or 50 percent."
It seems to show that we can get used to foods with less salt in it. So we could be healthier, and still enjoy our food just as much.
The problem is, there's no easy way to make this happen. Consumers aren't captives who can be forced to adapt.
Most of the salt that we eat comes via food that somebody else makes for us, such as bread, sandwich meat and salad dressing, and the companies that make those products aren't going to cut salt from them if they think it will drive consumers away.
"We'll always make sure these products taste good," says Todd Abraham, senior vice president for research and nutrition at Mondelez International, which makes Ritz crackers, Wheat Thins and Oreos. "If we produce products that are low-salt and consumers don't buy them, we haven't helped the American diet at all, because they'll go to a different product that has higher levels of salt."
A couple of years ago, a committee of scientists from the National Academy of Sciences' Institute of Medicine called on the government to help solve this problem with regulations.
Regulations, they pointed out, could force all the food companies to bring down salt levels in unison. There would be no high-salt alternatives, and consumers would eventually adapt to the new taste.
Food industry executives like Abraham don't like that idea. They say that such regulations are impractical. They also argue that regulations aren't necessary, because big food companies now are acting on their own. They are reducing salt levels, slowly and silently, in many processed foods. They're hoping that consumers won't even notice.