"Sodium Skeptics Try to Shake Up the Salt Debate"
High blood pressure is not the only harmful effect
of too much salt—
it’s also been tied with stomach cancer, kidney stones,
bone loss, obesity even,
direct damage to our kidneys and heart,
but as I reviewed before,
there is a consensus that dietary sodium plays
a significant role in raising people’s blood pressure
a dispute that has now finally been resolved.
So there’s this unequivocal evidence
that increased sodium intake is associated with increased blood pressure,
and we know that increased blood pressure leads to
increased risk of vascular diseases
like strokes, aneurisms, and atherosclerosis so,
to quote the long time editor-in-chief of the American Journal of Cardiology,
“We all must decrease our salt intake!”
as other authorities have echoed.
So how is the food industry
going to keep the salt controversy alive?
If salt leads to high blood pressure
and high blood pressure to disease—
if A leads to B and B leads to C then A should lead to C—
the logic seems sound.
Blood pressure is one of the best validated surrogate markers
for cardiovascular disease,
and when countries have tried cutting down on salt,
it seems to have worked.
Campaigns in England were able
to successfully bring down salt consumption,
blood pressures dropped,
and so did rates of heart disease and stroke.
Now they were also successfully able to bring down cholesterol levels
and smoking, and improved fruit and vegetables consumption,
but in Japan they dropped salt intake while eating a worse diet
and smoking more and STILL saw a large reduction
in stroke mortality.
Based on what they were able to achieve in Finland,
one daily teaspoon of salt may mean between 25 to 50%
more deaths from heart attacks and strokes.
But are there randomized controlled trials to show that?
They’ve never randomized people into two groups,
one low sodium, one not
and followed them out for 20 years to see
if the differences in blood pressure
translated into the expected consequences.
But for that matter, such a study has never been done
on smoking either.
Imagine randomizing a group of smokers to quit smoking
or stay smoking for ten years to see who gets lung cancer.
First of all, it’s hard to get people to quit,
just like it’s hard to keep people on a low salt diet,
and would it be ethical to force people to smoke
for a decade knowing from the totality of evidence
that it’s likely to hurt them?
That’s like the Tuskegee experiment.
We can’t let the perfect be the enemy of the good;
we’re never going to get a decade-long randomized trial,
but in 2007 we got this.
There have been randomized trials of sodium reduction,
but they haven’t lasted long enough
to provide enough data on clinical outcomes.
For example, the famous TOHP trials,
which randomized thousands
into at least 18 months of salt reduction.
What if you followed up with them 10 to 15 years
after the study was over figuring maybe some
in the low-salt stuck with it.
And indeed, cut sodium intake by 25 to 35%
and we may end up with 25% lower risk of heart attacks
and strokes and other cardiovascular events.
This was considered the final nail in the coffin for salt,
addressing the one remaining objection to universal salt reduction,
the first study to show not only a reduction in blood pressure,
but a reduction in hard end points—
morbidity and mortality—
by reducing dietary sodium intake.
Case closed, 2007.
But when billions of dollars are at stake the case is never closed.
One can just follow the press releases of the Salt Institute.
For example, what about the Institute of Medicine report
saying that sodium reduction may cause harm
in certain patients with decompensated congestive heart failure?
An analysis of those studies has since been retracted
out of concern that the data may have been falsified.
But it’s certainly possible that those with serious heart failure
already severely salt depleted by high dose salt-wasting drugs
may not benefit from further sodium restriction,
but for the great majority of the population
the message remains unchanged.
What about the new study
published in the American Journal of Hypertension
that found the amount of salt we are eating is just fine,
suggesting a kind of u-shaped curve
where too much sodium is bad,
but too little could be bad too?
But those biased less towards Big Salt
and more towards Big Heart
have noted that these studies have been widely misinterpreted,
stirring unnecessary controversy and confusion.
It basically comes down to three issues:
measurement error, confounding, and reverse causality.
All this data came studies that were not designed
to assess the relationship
and so tended to use invalid sodium estimates,
just because it’s hard to do the multiple 24 urine collections
necessary to get a good measurement.
And in the U.S. many of those eating less salt
are simply eating less food,
maybe because they’re so sick,
so no wonder they’d have higher mortality rates.
So compiling these studies together
is viewed as kind of garbage in garbage out.
But why would they do that—
they claim to have no conflicts of interest?
But when confronted with evidence showing at least one of the co-authors
received thousands of dollars from the Salt Institute,
they replied that well,
“they didn’t get more than $5,000 from them in the last 12 months,”
so that's how they could get out of saying they had a conflict of interest.
If you instead look only at the trials
in which they did the gold-standard 24-hour collections
in healthy people to avoid the reverse causation
and controlled for confounders,
the curve instead looks like this:
a continuous decrease of cardiovascular disease events
like heart attacks and strokes
as sodium levels get lower and lower,
a 17% increase in risk of CVD
for every gram of sodium a day.
And this is for people without high blood pressure,
for which we’d expect the benefit to be even greater.
Unfortunately, the media have widely misreported the findings
and a false sense of controversy has been broadcast,
confusing the public.
But it’s not just the media.
When editorials are published on the subject
in some of the most prestigious medical journals in the world,
you don’t expect them to be written by those
who got paid personal fees by Big Salt.
And before accepting money from the Salt Institute,
she was accepting money from the Tobacco Institute,
and was a frequent expert witness
in defense of Phillip Morris and other tobacco companies.
So if that’s who the New England Journal of Medicine
chooses to editorialize about salt,
you can see the extent of industry influence.
The editor-in-chief of the American Journal of Hypertension himself
worked for many years as a consultant to the Salt Institute.