"Sodium and Autoimmune Disease: Rubbing Salt in the Wound?"
Millions suffer from asthma attacks triggered by exercise.
Within 5 minutes of starting exercising,
people can get short of breath, start coughing and wheezing,
such that lung function significantly drops.
But, on a high-salt diet, the attack is even worse;
whereas, on a low-salt diet,
there’s hardly a significant drop in function at all.
To figure out why, researchers had them all cough up
sputum from their lungs, and those on the high-salt diet
ended up with triple the inflammatory cells
and up to double the concentration of inflammatory mediators.
But why?
What does salt intake have to do with inflammation?
We didn’t know...
until now.
The “Western diet,” high in saturated fat and salt,
has long been postulated as one potential cause
for the increasing incidence
of autoimmune diseases in developed countries.
The rapidly increasing incidence of autoimmune diseases
may be due to an over- activation of immune cells
called helper 17 cells.
The development of multiple sclerosis, psoriasis, type I diabetes,
Sjögren’s syndrome, asthma, and rheumatoid arthritis
has all been shown to involve this Th17-driven inflammation,
and one trigger for the activation of those Th17 cells
may be elevated levels of salt in our bloodstream.
The sodium content of processed foods and ‘fast food’
can be more than 100 times higher
in comparison to similar homemade meals.
And, sodium chloride, salt, appears to drive autoimmune disease
by the induction of these disease-causing Th17 cells.
Turns out, there’s a salt- sensing enzyme responsible
for triggering the formation of these Th17 cells.
Organ damage caused by high-salt diets
may also activate another type of inflammatory immune cell.
A high-salt diet can overwork the kidneys,
starving them of oxygen, triggering inflammation.
The more salt they gave people,
the more activation of inflammatory monocyte cells,
associated with high-salt intake induced kidney oxygen deficiency,
but this study only lasted two weeks.
What about long term?
One of the difficulties in doing sodium experiments
is that it’s hard to get free-living folks
to maintain a specific salt intake.
You can do what are called metabolic ward studies,
where you essentially lock people in a hospital ward
for a few days and control their food intake,
but you can’t do that long term, unless...
you can lock people in a space capsule.
Mars520 was a 520-day space flight simulation
to see how people might do on the way to Mars and back.
What they found was that those on a high-salt diet
displayed a markedly higher number of monocytes,
which are a type of immune cell you often see increased
in settings of chronic inflammation and autoimmune disorders.
This may reveal one of the consequences
of excess salt consumption in our everyday lives,
since that so-called high-salt intake may actually
just be the average salt intake.
Furthermore, there was an increase in the levels
of pro-inflammatory mediators
and a decrease in the level of anti-inflammatory mediators,
suggesting that high-salt diets have a potential to bring about
an excessive immune response, which may damage the immune balance
and result in either difficulties
in getting rid of inflammation or
even an increased risk of autoimmune disease.
What if you already have an autoimmune disease?
Sodium intake is associated with increased disease activity
in multiple sclerosis.
If you follow MS patients for a few years,
those eating more salt
had 3 to 4 times the exacerbation rate;
three times more likely to develop
new MS lesions in their brains,
and on average, had 8 more brain lesions,
14 in their brain compared to
6 in the low-salt group.
So, the next step is to try treating patients
with salt reduction and see if they get better.
But since reducing our salt intake
is a healthy thing to do anyway,
I don’t see why anyone should have to wait.