New York Times science reporter John Tierney has an excellent article today on New York City's Mayor Bloomberg's attempt to rip salt shakers from the hands of the Big Apple's diners. The reason: allegedly to improve their health. But as Tierney shows, such public health fascism can have unintended consequences:
Suppose you wanted to test the effects of halving the amount of salt in people's diets. If you were an academic researcher, you'd have to persuade your institutional review board that you had considered the risks and obtained informed consent from the participants.
You might, for instance, take note of a recent clinical trial in which heart patients put on a restricted-sodium diet fared worse than those on a normal diet. In light of new research suggesting that eating salt improves mood and combats depression, you might be alert for psychological effects of the new diet. You might worry that people would react to less-salty food by eating more of it, a trend you could monitor by comparing them with a control group.
But if you are the mayor of New York, no such constraints apply. You can simply announce, as Michael Bloomberg did, that the city is starting a "nationwide initiative" to pressure the food industry and restaurant chains to cut salt intake by half over the next decade. Why bother with consent forms when you can automatically enroll everyone in the experiment?
Tierney then goes on to detail the scientific evidence that suggests that cutting back on salt will not have the salutary effects the mayor and other health nazis expect:
First, a reduced-salt diet doesn't lower everyone's blood pressure. Some individuals' blood pressure can actually rise in response to less salt, and most people aren't affected much either way. The more notable drop in blood pressure tends to occur in some — but by no means all — people with hypertension, a condition that affects more than a quarter of American adults.
Second, even though lower blood pressure correlates with less heart disease, scientists haven't demonstrated that eating less salt leads to better health and longer life. The results from observational studies have too often been inconclusive and contradictory. After reviewing the literature for the Cochrane Collaboration in 2003, researchers from Copenhagen University concluded that "there is little evidence for long-term benefit from reducing salt intake."
A similar conclusion was reached in 2006 by Norman K. Hollenberg of Harvard Medical School. While it might make sense for some individuals to change their diets, he wrote, "the available evidence shows that the influence of salt intake is too inconsistent and generally too small to mandate policy decisions at the community level."
In the past year, researchers led by Salvatore Paterna of the University of Palermo have reported one of the most rigorous experiments so far: a randomized clinical trial of heart patients who were put on different diets. Those on a low-sodium diet were more likely to be rehospitalized and to die, results that prompted the researchers to ask, "Is sodium an old enemy or a new friend?" …
Salt deprivation might also darken your mood, according to recent research by Alan Kim Johnson and colleagues at the University of Iowa. After analyzing the behavior and brain chemistry of salt-deprived rats, the psychologists found that salt, like chocolate and cocaine, affected reward circuitry in the brain, and that salt-deprived rats exhibited anhedonia, a symptom of depression characterized by the inability to enjoy normally pleasurable activities.