Deficits, immigration and salt
The May 17 edition of National Review Online contained an article entitled "Salt Sense" by Bruce Bartlett. The article makes the point that budget deficits and immigration (legal and illegal) "are benign up to a point." So far, so good. But Mr. Bartlett introduces the concept comparing it to dietary salt intake.
Analogy is a powerful tool. Painting mental pictures embeds thoughts into memory. Mistaken analogies either perpetuate error or undermine the author's argument. Since Paracelsus, we've all understood that "the dose makes the poison" and that all organisms can tolerate sub-toxic exposures (perhaps we should exempt the State of California's Proposition 65 from this generous assessment). But Mr. Bartlett's "favorite example" is mythologic. "Too much salt," he says, can be problematic. Sure. "Too much" of anything, by tautologous definition, is excessive. His implication is clear: above some amount that humans might ingest, "salt can create physical problems such as high blood pressure." That may be Mr. Bartlett's opinion, but not a medical consensus. He continues that "a large quantity of salt consumed within a short time will kill you." Misleading at best. If a human were fed any substance intravenously, such as increasing the concentration of the perfectly safe saline used in emergency medical procedures, doubtless it could be fatal, but humans cannot ingest such amounts; their intolerant stomachs would rebel and regurgitate such amounts. As for blood pressure, we've known for four millenia of the relationship of salt and blood pressure, but there is no consensus that salt intake "causes" hypertension ("high blood pressure," a defined medical term). Hypertension is an important indicator of "physical problems" but, itself, only a risk factor, not a health outcome. We are rightly concerned that blood pressure is a strong predictor of adverse health outcomes such as heart attacks, but there are other risk factors involved. Not a single study examining the relationship between the amount of salt consumed in the American diet and either heart attack rate or to how long people live, has found that "excessive" salt intake is associated with higher rates of heart attacks or with lower mortality . In fact, the latest study, by the current president of the International Society of Hypertension, published in the March issue of the American Journal of Medicine , found that Americans who ingest the government-recommended amount of salt, actually had a 37% higher mortality. Low-salt dieters died more frequently. This is because salt serves multiple metabolic purposes and reducing salt, for example, increases insulin resistence, a risk factor for diabetes, and plasma renin activity, a strong predictor of myocardial infarction. There is no controlled trial showing that reducing dietary salt improves health outcomes. None of this, of course, should impune Mr. Bartlett's logic: the dose, indeed, makes the poison. It's unfortunate that his easy adoption of a popular myth in his "favorite example" might tend to undermine the credibility of his argument.
