Tuesday, April 07, 2009

Food police don't need no stinkin' controlled study

John Tierney takes on Mayor Bloomberg's diktat to New York city restaurants and food industry to halve the population's salt intake. Tierney cites all sorts of conflicting evidence on the benefits of limiting our salt intake.
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?”

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. (See original for links.)
But being one of those liberals who purports to know what is best for us, Mayor Bloomberg and his health commissioner don't need to look at controlled studies to see what the effects of reducing salt would be on an entire, diverse population. They know what's better for everyone and so they will implement their wisdom. Heck, the government knew what was best for us when we had that old food pyramid recommending limited fat consumption, didn't it? Actually, not so much.
That antifat campaign, like the antisalt campaign, was endorsed by prominent groups and federal agencies before the campaigners’ theory was tested in rigorous trials. It too seemed quite logical — in theory.

But in practice the results were dismal, as demonstrated eventually by clinical trials and by the expanding waistlines of Americans. People followed the advice in the “food pyramid” to reduce the percentage of fat in the diet, but they got more obese, perhaps because they ate so many other ingredients in foods with “low fat” labels.
It's nice that the Mayor of New York City has solved all the other problems facing that city today so that he can move on to the salt consumption of its inhabitants. But some of the rest of us prefer to wait for more research before we take Bloomberg's say-so for our diet.