"The Evidence that Salt Raises Blood Pressure"
Like any group with vested interests,
the food industry resists regulation.
Faced with a growing scientific consensus
that salt increases blood pressure,
major food manufacturers have adopted desperate measures
to try to stop governments
from recommending salt reduction.
Rather than reformulate their products and save lives,
manufacturers have lobbied governments,
refused to cooperate, encouraged misinformation campaigns,
and tried to discredit the evidence.
After all, salt is the main source
of flavor in processed foods.
Of course they could improve the flavor
by adding real ingredients,
but like making a pop-tart with actual strawberries
would be more expensive and cut into profits.
The evidence that they’re trying to discredit
includes double-blind, randomized trials
dating back decades.
You take people with h igh blood pressure,
put them on a sodium- restricted diet,
and their blood pressure drops.
Then if you keep them on the low salt diet
and add a placebo, nothing happens.
But if you instead give them salt
in the form of a time- release sodium pill,
their blood pressure goes back up.
And the more sodium you secretly give them,
the higher their blood pressure climbs.
Even just a single meal can do it.
If you take people with normal blood pressure
and give them a bowl of soup
containing how much salt a regular meal might contain,
and your blood pressure goes up over the next 3 hours
compared to the same soup with no added salt.
Why though?
High blood pressure appears to be our body’s way
to push the excess salt out of our system.
Dozens of such studies have been done,
showing that if we reduce our salt intake
we reduce our blood pressure,
and the greater the reduction the greater the benefit.
The so-called DASH diet, which I’ve covered before,
is commonly used to capture the blood pressure benefits
of more plant-based populations,
but how do we know the benefits had anything to do
with eating less salt
instead of just from eating more fruits and vegetables,
because it was put to the test.
Sure eating healthier lowers blood pressure
no matter how much salt we eat,
but even if we stick to the same diet,
lowering salt helps independently of other dietary improvements.
You can do this on a community level.
You take two matched villages
that both start out about the same.
In the control village, on average,
blood pressures went up or stayed the same.
But in the village where they were able to cut down
on salt intake, blood pressures went down.
Whereas if we don’t cut down, chronic high salt intake
can lead to a gradual increase in blood pressure throughout life,
as shown in the famous Intersalt study.
52 centers from 32 countries participated
with hundreds of participants each
and four of those centers were in populations
that ate so little salt they actually complied
with the American Heart Association guidelines for salt reduction,
something less than 1% of Americans achieve.
In a population where everyone makes the cut off,
not only was not a single case of high blood pressure was found,
but the older folks have the same blood pressure
as the teenagers.
This is why including such populations is so important.
If you just look at the 48 centers
in the industrialized Western world,
there does not appear to be any relationship
between rising blood pressure with age
and how much sodium people are getting every day.
Just looks like a random assortment of dots.
Now the salt industry looks at this
and says aha—see I told you so,
no relationship between salt and increasing blood pressures
as you get older.
But maybe that’s because they’re all getting too much salt.
The American Heart Association recommendation
is that everyone get their salt intake under here,
so they were all way over.
You can imagine a similar result
if this was instead lung cancer rates
versus packs of cigarettes smoked every year.
Whether you smoked 150 packs a year or 200 packs a year,
it might not make much of a difference.
To see a relationship between smoking and cancer,
you’d have to compare smokers to those who rarely light up.
And indeed, if you add in t hose low-salt populations
that get little or no high blood pressure as they get older,
and you end up with a highly statistically significant
relationship between increasing sodium
and increasing blood pressure,
but only if you include people that actually comply
with the salt guidelines.
As with so many lifestyle interventions,
they only work if you actually do it.