Although recommendations haven't changed much since the first dietary guidelines were issued, The McGovern Report, in the late 1970's, one deafening
mantra has steadily and adamantly been force fed to us from researchers and doctors to caring brothers and sisters: Eat less salt and you'll lower
hypertension and decrease your risk for developing heart disease and dying of a heart attack.
The Dietary Goals for the United States, found in The McGovern Report, was issued in 1977 found
The notion that excess salt consumption could induce hypertension has been around since doctors in the early 1900's noticed patients with hypertension
had a propensity to eat salt almost ravenously; however, ambiguity shrouded the body of research surrounding the association between hypertension and
dietary salt consumption. Consistently inconsistent wouldn't be putting it lightly. That all came to an end in 1972 when Lewis Dahl, a New York
physician, clinically induced hypertension in lab rats showing inconclusively that excess salt consumption unequivocally causes high blood pressure.
However, according to the data, as Gary Taubes pointed out in his award winning piece titled
The Political Science of Salt
issued in Science in 1999, the term "excess" was a
bit of a stretch:
Dahl's rats became hypertensive only if fed an amount of salt equivalent to more than 500 grams a day for an adult human
Regardless, public health authorities deemed salt a nutritional foe in the battle against hypertension and heart disease despite a lack of consensus
among researchers. And over the last 3 decades nothing has changed. The US Dietary Guidelines, issued jointly by the USDA and HHS every 5 years,
still recommends that EVERYBODY reduce their salt intake by half (the average American consumes around 9g of salt per day), citing studies that
support the recommendation and dismissing/ignoring contradictory evidence (a debate which has become even more enveloped in ambiguity since 1977).
Over the past few weeks, a few studies have shaken the foundation that forms the recommendation to reduce salt intake. The most damning undoubtedly
comes from a meta-analysis conducted by the Cochrane Collaboration
, called a Cochrane Review. Its
significance stems from the quality of work notoriously produced in their systematic reviews:
Cochrane Review is a scientific investigation in itself, with a pre-planned Methods section and an assembly of original studies (predominantly
randomised controlled trials and clinical controlled trials, but also sometimes, non-randomised observational studies) as their ‘subjects’. The
results of these multiple primary investigations are synthesized by using strategies that limit bias and random error. These strategies include a
comprehensive search of all potentially relevant studies and the use of explicit, reproducible criteria in the selection of studies for review.
Primary research designs and study characteristics are appraised, data are synthesized, and results are interpreted.
When these guys have something to say, it's best to shut-up and listen.
Published in the American Journal of Hypertension on July 6th, 2011, the Cochrane Review delivered a significant blow to the anti-salt
Reduced Dietary Salt for the Prevention of Cardiovascular Disease: A
Meta-Analysis of Randomized Controlled Trials (Cochrane Review)
Background: Although meta-analyses of randomized controlled trials (RCTs) of salt reduction report a reduction in the level of blood pressure
(BP), the effect of reduced dietary salt on cardiovascular disease (CVD) events remains unclear.
Methods: We searched for RCTs with follow-up of at least 6 months that compared dietary salt reduction (restricted salt dietary intervention or advice
to reduce salt intake) to control/no intervention in adults, and reported mortality or CVD morbidity data. Outcomes were pooled at end of trial or
longest follow-up point.
Results: Seven studies were identified: three in normotensives, two in hypertensives, one in a mixed population of normo- and hypertensives and one in
heart failure. Salt reduction was associated with reductions in urinary salt excretion of between 27 and 39 mmol/24 h and reductions in systolic BP
between 1 and 4 mm Hg. Relative risks (RRs) for all-cause mortality in normotensives and hypertensives showed no strong evidence of any effect of salt
reduction CVD morbidity in people with normal BP and raised BP at baseline also showed no strong evidence of benefit. Salt restriction increased the
risk of all-cause mortality in those with heart failure.
Our finding of a lack of strong evidence of an effect of dietary sodium reduction on mortality and CVD outcomes is in contrast to those of Strazzullo
and colleagues, who systematically reviewed prospective observational studies that examined the relationship between dietary sodium and all-cause
mortality and CVD mortality
Essentially, salt restriction isn't really working. In fact, restricting salt in those with heart failure was associated with an increased risk of
In another study published in JAMA recently, similar results were found.
Fatal and Nonfatal Outcomes, Incidence of Hypertension, and Blood Pressure Changes in
Relation to Urinary Sodium Excretion
Conclusions 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.
Once again, salt restriction was associated with higher Cardiovascular disease mortality. Over the past 30 years, there have been many studies
published showing almost identical results. These aren't cherry picked, low-quality studies.
What can you take from all of this? Most quality studies on salt restriction show a modest decrease in blood pressure and an even smaller decrease in
preventing Cardiovascular death when subjects reduce their salt intake by half. It's also clear that genetic influences can cause hypersensitivity to
salt consumption. For those, salt reduction would be extremely beneficial; however, blanket recommendations to the general public to lower salt
intake is simply irresponsible.
You can stop here if you just wanted the facts about salt consumption, as from this point forward I'll be providing my own interpretation of the
recently published studies.
What kills me is something that seems to have been overlooked by researchers and journalists reporting on these two studies. It's something that
jumped off the page so obvious to me that it almost baffling. In the later study quoted, the last sentence in the conclusion read:
Lower sodium excretion was associated with higher CVD mortality.
The Cochrane Review found similar results.
This here, to me, is the tell-tale signature of the real problem at hand. Salt restriction doesn't really work because, typically, the body is able
to excrete excess sodium through urination and even sweating. However, certain metabolic conditions can prevent this. Hyperinsulinemia, chronically
elevated blood insulin, is present in those with Insulin Resistance and type II diabetes. Well, if you remember from your biochemistry class in
school, elevated insulin levels cause sodium retention.
There's a reason why Type II Diabetics are prone to developing hypertension and heart disease quicker than non-diabetics. These studies have shown
that low sodium excretion, or sodium retention, is associated with cardiovascular events and death.
Sodium retention caused by elevated insulin levels leads directly to hypertension. It's not the dietary salt. It's elements of the diet that are
decreasing insulin sensitivity and increasing insulin levels. In diabetics, a simple carbohydrate restriction does wonders. Low-carb diets work so
quickly because the first weight to drop is from water excretion...because insulin levels quickly lower and sodium is excreted.
Researchers are so busy arguing over the symptom of the real problem. It certainly explains the ambiguity and inconsistency in the data when
researchers focus on dietary salt consumption.
Anyway, out of all of this, one thing is clear: If you're a somewhat healthy individual, cutting your salt intake by half won't make you live
longer. And if you aren't healthy, it really is unclear whether salt restriction is beneficial or detrimental.
edit on 17-7-2011 by
DevolutionEvolvd because: (no reason given)