For eight years, researchers followed 3,681 Europeans—healthy middle-aged people who didn't have high blood pressure or heart disease. They observed each participant's salt intake by measuring the sodium in their urine and measured their blood pressure. What they found, published in a study in the latest issue of the Journal of the American Medical Association, continues to stoke the flames of one of the biggest food fights: the assault on salt.
The investigators claim that the less salt people ate, the more likely they were to die of heart disease—and that a modest increase in salt did not appear to cause high blood pressure.
These results contrast with evidence showing the opposite effect, including the 1988 Intersalt study (below), which correlated high salt intake (on the x axis) with the percentage of the population exhibiting high blood pressure (on the y axis). Public health officials generally agree, and the Center for Disease Control openly criticized the most recent study, saying it should be "taken with a grain of salt."
This latest study just adds to the general confusion about how—and whether—people should regulate the levels of salt in their diets.
For starters, salt is a primary determinant of taste in food—fat, of course, is the other—and 80% of the salt we consume comes from processed foods, making it difficult to avoid. Then there's the kicker: While the government has been denouncing salt as a health hazard for decades, no amount of scientific effort has been able to dispense with the suspicions that it is not. Indeed, the controversy over the benefits, if any, of salt reduction now constitutes one of the longest running, most vitriolic, and surreal disputes in all of medicine.
Making things even more complicated, we can't even blame processed foods alone for our current salt intake since we were using similar amounts of salt to preserve meats, pickles, or ketchup thousands of years ago. In a 2010 report from the Institute of Medicine:
In an estimate of early usage, the average daily sodium intake in certain parts of China in 300 B.C. was reported to be nearly 3,000 mg/d for women and 5,000 mg/d for men. Multhauf estimated that, in France and Britain in 1850, the human culinary intake of sodium was 4,000–5,000 mg/d.
So if scientists can't agree on whether excess salt consumption is prematurely killing us, should we hold off on policies that cut salt? Well, as one researcher told Taubes, salt may be a case where the science actually destabilizes public policy; studies like the one published today shouldn't influence a broader preventative agenda.
And, as I've argued before, salt is often merely added to unpalatable, ultra-processed ingredients to make them taste like food. Eating fewer of these foods is probably a good idea—and not just because they're salty.