Part 1
by Jeffrey Dach MD
Low Salt Diet Found to Increase Mortality The Low Salt Diet Revisited
A recent Lancet study on the effect of a low salt diet made headlines, finding that a low salt diet increases mortality for patients with congestive heart failure.(1-6) The study concluded there was not enough evidence to advise a low-salt diet for the rest of us. They doubted a low salt diet would benefit the population.(6) In this article we will re-examine the low salt diet, clear away the confusion, and make recommendations about salt intake, hypertension, and health.
Health Benefits of Salt
We know from many years of published studies that increasing salt intake increases blood volume and also blood pressure. Salt is essential for maintaining blood volume, blood pressure, and overall health. The salt content of blood is similar to ocean water. Both have sodium chloride, also known as salt.
Importance of Salt
One example of the importance of salt is the common practice of starting an intravenous solution of salt and water as the first line treatment for the trauma patient upon arrival to the hospital Emergency Room.
Low Salt Diet to Reduce Blood Pressure
One of the central dogmas of mainstream medicine is the “low salt diet” as a treatment for reducing blood pressure in the hypertensive patient. Indeed, popular wisdom says that the “low salt diet” is also healthy for the rest of us “normal” people who don’t have hypertension.(25) Along with the rest of my medical school class, I was indoctrinated to believe this. Is this really true? Many studies have looked at this question. They show the “low salt diet” will in fact reduce blood pressure slightly. However, this effect is minimal, and is counteracted by compensatory mechanisms that release harmful substances into the bloodstream, hormones and chemical mediators that counteract the “low salt diet”. The released chemical mediators include insulin, epinephrine, norepinephrine, renin, aldosterone, etc. These are harmful and damaging to the vascular system. (7-11)
Low Salt Diet Increases Cardiovascular Mortality
In addition, a number of studies have found that a “low salt diet” increases cardiovascular mortality. (5) A study published in the 1995 Hypertension found 4.3 times greater mortality in hypertensive men on a low salt diet.(12) They also found higher plasma renin in these men, a hormone produced by the body which causes salt and water retention by the kidney to compensate for the low salt diet.(12-15)
A 2011 JAMA provides the reasons for this increased mortality and says … (16)
The underlying mechanisms explaining the inverse association between cardiovascular mortality and 24-hour urinary sodium excretion might be that a salt intake low enough to decrease blood pressure also increases sympathetic nerve activity, decreases insulin sensitivity, activates the renin-angiotensin system, and stimulates aldosterone secretion. (16)A 1998 JAMA report found that a low salt diet increased plasma renin 3.6-fold and aldosterone by 3.2-fold, increases that were proportional to the degree of sodium restriction. (17) The authors also reported the “low salt diet” increased other harmful substances such as noradrenaline, cholesterol, and low-density lipoprotein cholesterol (LDL). (17) A 1999 report in American Journal of Hypertension found that “moderate salt restriction aggravates both systemic and vascular insulin resistance.” (18)
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Read the complete article here.
Low Salt Diet Part Two
In Part One, we discussed the low salt diet, and studies which show an increased mortality from a salt restricted diet. You may have been wondering about this if you saw a recent article in the New York Times by Jane Brody extolling the virtues of a low salt diet.(1) Jan Brody quotes a computer simulation model that predicted 500,000 lives saved by eliminating dietary salt in a program similar to Finland which was described in a New England Journal article.(2,3)
Gary Schwitzer does a good job on their blogs explaining where the Jane Brody article goes wrong.(4,5).
Research by Jan A. Staessen, MD, PhD, of the University of Leuven in Belgium and colleagues, raises questions regarding whether population-wide sodium restriction will actually lower cardiovascular risks. (5,6) In actually clinical studies where 24 hr sodium excretion is measured in 3681 participants and followed over 8 years, this is what they found:
In this population-based cohort, systolic blood pressure, but not diastolic pressure, changes over time aligned with change in sodium excretion, but this association did not translate into a higher risk of hypertension or CVD complications. Lower sodium excretion was associated with higher CVD mortality.(5,6)
I would agree with Jane Brody that hypertension, heart disease and other health problems are a direct result of diets containing large amounts of processed salt (NaCl), Trans Fats, Sugars, MSG, Aspartame, GMO corn and GMO Soy, and added wheat fillers. To focus attention on the salt content alone, while ignoring the other harmful additives may be not be a valid exercise.
The “low salt diet” for reducing blood pressure in the hypertensive patient is a central dogma of mainstream medicine. Indeed, popular wisdom says that the “low salt diet” is also healthy for the rest of us “normal” people who don’t have hypertension. Along with the rest of my medical school class, I was indoctrinated to believe this. Is this really true? Many studies have looked at this question. They show the “low salt diet” will in fact reduce blood pressure slightly. However, this effect is minimal, and is counteracted by compensatory mechanisms that release harmful substances into the bloodstream, that counteract the “low salt diet”. The released chemical mediators include insulin, epinephrine, norepinephrine, renin, aldosterone, etc. These are harmful and damaging to the vascular system.
In addition, a number of studies have found that a “low salt diet” increases cardiovascular mortality. A study published in the 1995 Hypertension found 4 times greater mortality in hypertensive men on a low salt diet.
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Read the complete article here.
This new link added April 30, 2013: WebMD offers dangerous junk science-based dietary salt advice… This article states that "… even though one of its cited “experts” tacitly admits there is no established cause-and-effect relationship between typical/normal/current salt intake and adverse health effects."
Another article from Food Politics by Marion Nestle found here and
here: http://news.nationalpost.com/2013/09/22/little-evidence-sharp-reductions-in-salt-consumption-will-improve-health-heart-researcher-says/
More data in the Salt Wars - Aug 14, 2014; http://www.medpagetoday.com/Cardiology/Hypertension/47203
An article by Marion Nestle - http://www.foodpolitics.com/2014/08/its-salt-arguments-again-new-research-arguments-over-public-health-recommendations-and-issues-of-conflicts-of-interest/
