Motus Mentis

The mayor of New York City, Michael Bloomberg, is something of a contradiction: though a Republican, he is a committed nanny-stater. A little while back he led an initiative to outlaw the serving of trans-fats in Gotham’s restaurants, and he offered praise for Governor Patterson’s ridiculous and insulting “obesity tax” on soda pop. Now he is on a crusade to exert control in loco parentis over another of Gotham’s dietary choices: the amount of salt we eat.

As readers might imagine, this does not sit well with the generally libertarian outlook of the waka waka waka editorial board. It apparently also doesn’t sit well with Times columnist John Tierney, who wrote a sharply disapproving item in Tuesday’s Science section.

Quite obviously the question of whether the government should be interfering in the first place with the liberty of supposedly free adults to buy and sell salty foods if they want to is central here, but so bad is this idea in so many ways that Mr. Tierney is able to leave that issue aside altogether and still devote a substantial article to this misbegotten initiative’s other faults. In particular, he points out that Mr. Bloomberg, secure as usual in his overweening confidence and ideological certainty, is blithely and regally circumventing the patient and rigorous methods by which scientific inquiry investigates such matters. We read:

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?

And why bother with a control group when you already know the experiment’s outcome? The city’s health commissioner, Thomas R. Frieden, has enumerated the results. If the food industry follows the city’s wishes, the health department’s Web site announces, “that action will lower health care costs and prevent 150,000 premature deaths every year.’

But that prediction is based on an estimate based on extrapolations based on assumptions that have yet to be demonstrated despite a half-century of efforts. No one knows how people would react to less-salty food, much less what would happen to their health.

What His Honor obviously considers a no-brainer is hardly a settled matter as far as actual research is concerned:

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.’

Indeed, it appears that salt restriction may have undesirable results:

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?’

Those results, while hardly a reason for you to start eating more salt, are a reminder that salt affects a great deal more than blood pressure. Lowering it can cause problems with blood flow to the kidneys and insulin resistance, which can increase the risk of strokes and heart attacks.

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.

Given all of this, you would think that Mr. Bloomberg might, as any of the rest of us would, be troubled by doubts. But if so, dear Reader, you do not know our diminutive plutocrat as we Gothamites do; he is not one to reflect on the limitations of mortal wisdom (not his own, anyway), nor on the many and sorrowful lessons of hubris that darken the pages of history and literature. No, he’ll have his bill, all right, unless we push back good and hard, and I salute Mr. Tierney for doing so.

Read his essay here.