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Their primary goal was to assess the effect of such interventions on mortality and cardiovascular morbidity as well as to determine whether or not blood pressure was the causal factor. The authors concluded that "the benefits from dietary salt restriction are consistent with the predicted small effects on clinical events attributable to the small blood pressure reduction achieved."
In other words, "cutting down the amount of salt has no clear benefits in terms of dying or experiencing cardiovascular disease." Furthermore, individuals in the study populations who were suffering from congestive heart failure actually showed and increased risk of all-cause mortality, which led the researchers to state that "Further research in needed to confirm our finding that dietary advice to reduce salt may increase deaths in people with heart failure."
In a review of the findings, the Wall Street Journal interviewed Morton Satin, vice president of science and research at the Salt Institute, who, despite his obvious interest in salt being viewed as harmless, made a particularly salient (no pun intended) point that "We have all heard the twin salt reduction refrain, ‘Lower your salt consumption and you will reduce your blood pressure,’ immediately followed by ‘Lower blood pressure reduces heart disease and saves thousands of lives. The anti-salt lobby never says explicitly, ‘Lowering salt consumption will reduce heart disease and save thousands of lives.’ This is because two half truths don’t make one whole truth.”
In his book "Good Calories, Bad Calories", author Gary Taubes takes on the perceived salt-hypertension-heart disease connection by noting that "once the salt hypothesis raised the possibility that diet was responsible, investigators began to perceive the presence or absence of hypertension in isolated populations purely as a test of the salt hypothesis." He goes on to state that, "Since hypertension only appeared in these populations when they gained access to western diets, which frequently included salt-rich processed foods, the investigators saw their studies as confirming the salt hypothesis."
Conspicuously absent in these discussions of isolated populations and the emergence of hypertension was that other novel foodstuffs, namely sugar and white flour, appeared in traditional diets at the same time additional salt did. Despite this deliberate or intentional oversight, the "absence of hypertension in isolated populations eating their traditional diets was still the most compelling evidence in support of the (salt) hypothesis."
In a 1977 conference on obesity, George Bray stated that "...it is now well-established that a low-carbohydrate diet is followed by the excretion of water and that carbohydrate ingestion leads to retention of both salt and water." The precise mechanism of this action was described by Walter Bloom, the director of research at Piedmont Hospital in Atlanta Georgia. Taubes explains Bloom's research by describing a process by which "the water lost on carbohydrate-restricted diets is caused by a reversal of the sodium retention that takes place routinely when we eat carbohydrates."
That dietary carbohydrate impairs the bodies ability to excrete salt, thereby raising the concentration of sodium in the body has been overshadowed by the more popular notion of eliminating salt from the diet of heart-disease patients. Even though "removing carbohydrates from the diet works, in effect, just like the anti-hypertensive drugs known as diuretics, which cause the kidneys to excrete sodium, and water along with it."
In addition to impairing sodium excretion, the consumption of dietary carbohydrate causes the release of insulin, which can affect blood pressure by "stimulating the nervous system and the same flight-or-fight response incited by adrenaline." Harvard Medical School endocrinologist Lewis Landsberg is credited with this finding and showed that "by stimulating the activity of the nervous system, insulin increases heart rate and constricts blood vessels, thereby raising blood pressure." This research too, was swept under the rug.
Although the Cochrane Library researchers did not intend to question the salt hypothesis, their inability to find convincing evidence is one strike against the weak salt-heart disease connection and another opportunity to open discussion as to the more likely causes of heart disease, hypertension, and obesity.
Reduced Dietary Salt for the Prevention of Cardiovascular Disease: A Meta-Analysis of Randomized Controlled Trials (Cochrane Review). Rod S. Taylor, Kate E. Ashton, Tiffany Moxham, Lee Hooper and Shah Ebrahim
"Good Calories, Bad Calories" by Gary Taubes, pages 148, 150-51.