Take U.S.D.A. and C.D.C. Advice with a Grain of Salt
(p. 8) When I spent the better part of a year researching the state of the salt science back in 1998 -- already a quarter century into the eat-less-salt recommendations -- journal editors and public health administrators were still remarkably candid in their assessment of how flimsy the evidence was implicating salt as the cause of hypertension.
"You can say without any shadow of a doubt," as I was told then by Drummond Rennie, an editor for The Journal of the American Medical Association, that the authorities pushing the eat-less-salt message had "made a commitment to salt education that goes way beyond the scientific facts."
While, back then, the evidence merely failed to demonstrate that salt was harmful, the evidence from studies published over the past two years actually suggests that restricting how much salt we eat can increase our likelihood of dying prematurely. Put simply, the possibility has been raised that if we were to eat as little salt as the U.S.D.A. and the C.D.C. recommend, we'd be harming rather than helping ourselves.
. . .
When researchers have looked at all the relevant trials and tried to make sense of them, they've continued to support Dr. Stamler's "inconsistent and contradictory" assessment. Last year, two such "meta-analyses" were published by the Cochrane Collaboration, an international nonprofit organization founded to conduct unbiased reviews of medical evidence. The first of the two reviews concluded that cutting back "the amount of salt eaten reduces blood pressure, but there is insufficient evidence to confirm the predicted reductions in people dying prematurely or suffering cardiovascular disease." The second concluded that "we do not know if low salt diets improve or worsen health outcomes."
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(p. 9) 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.
. . .
One could still argue that all these people should reduce their salt intake to prevent hypertension, except for the fact that four of these studies -- involving Type 1 diabetics, Type 2 diabetics, healthy Europeans and patients with chronic heart failure -- reported that the people eating salt at the lower limit of normal were more likely to have heart disease than those eating smack in the middle of the normal range. Effectively what the 1972 paper would have predicted.
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Maybe now the prevailing beliefs should be changed. The British scientist and educator Thomas Huxley, known as Darwin's bulldog for his advocacy of evolution, may have put it best back in 1860. "My business," he wrote, "is to teach my aspirations to conform themselves to fact, not to try and make facts harmonize with my aspirations."
For the full commentary, see:
(Note: ellipses added.)
(Note: the online version of the commentary has the date June 2, 2012.)