The idea that eating less salt can worsen health outcomes may sound bizarre, but it also has biological plausibility and is celebrating its 40th anniversary this year, too. A 1972 paper in The New England Journal of Medicine reported that the less salt people ate, the higher their levels of a substance secreted by the kidneys, called renin, which set off a physiological cascade of events that seemed to end with an increased risk of heart disease. In this scenario: eat less salt, secrete more renin, get heart disease, die prematurely.
With nearly everyone focused on the supposed benefits of salt restriction, little research was done to look at the potential dangers. But four years ago, Italian researchers began publishing the results from a series of clinical trials, all of which reported that, among patients with heart failure, reducing salt consumption increased the risk of death.
Those trials have been followed by a slew of studies suggesting that reducing sodium to anything like what government policy refers to as a “safe upper limit” is likely to do more harm than good. These covered some 100,000 people in more than 30 countries and showed that salt consumption is remarkably stable among populations over time. In the United States, for instance, it has remained constant for the last 50 years, despite 40 years of the eat-less-salt message. The average salt intake in these populations — what could be called the normal salt intake — was one and a half teaspoons a day, almost 50 percent above what federal agencies consider a safe upper limit for healthy Americans under 50, and more than double what the policy advises for those who aren’t so young or healthy. This consistency, between populations and over time, suggests that how much salt we eat is determined by physiological demands, not diet choices.