Scimex: A high-salt diet may offer increased protection against skin infections,
a German and US study has found. The study found mice that ate a diet
high in salt had increased sodium accumulation on their skin which
boosted their immune response to a skin-infecting microbes. The authors
say salt may have been an ancient strategy to warn of infections before
the invention of antibiotics.
Most people consume more salt than they need and therefore have a higher
risk of heart disease and stroke, which are the two leading causes of
death worldwide. But a study published by Cell Press March 3rd in Cell
Metabolism reveals that dietary salt could have a biological advantage:
defending the body against invading microbes. A high-salt diet increased
sodium accumulation in the skin of mice, thereby boosting their immune
response to a skin-infecting parasite. The findings suggest that dietary
salt could have therapeutic potential to promote host defense against
microbial infections.
"Up to now, salt has been regarded as a detrimental dietary factor; it
is clearly known to be detrimental for cardiovascular diseases, and
recent studies have implicated a role in worsening autoimmune diseases,"
says first study author Jonathan Jantsch, a microbiologist at
Universitätsklinikum Regensburg and Universität Regensburg. "Our current
study challenges this one-sided view and suggests that increasing salt
accumulation at the site of infections might be an ancient strategy to
ward off infections, long before antibiotics were invented."
Large amounts of sodium stored in the skin, especially in older
individuals, can lead to high blood pressure and increase the risk for
heart disease and stroke. A high-salt diet, which increases sodium
storage in the skin, can also worsen autoimmune disease and even
increase the risk of stomach cancer. "Despite the overwhelming evidence
linking dietary salt to disease in humans, the potential evolutionary
advantage of storing so much salt in the body has not been clear," says
senior study author Jens Titze, who studies the link between sodium
metabolism and disease at Vanderbilt University School of Medicine.
A clue to this mystery came when Titze and his collaborators noticed an
unusually high amount of sodium in the infected skin of mice that had
been bitten by cage mates. Intrigued by this observation, Titze teamed
up with Jantsch to examine the link between infection and salt
accumulation in the skin. They found that infected areas in patients
with bacterial skin infections also showed remarkably high salt
accumulation. Moreover, experiments in mice showed that a high-salt diet
boosted the activity of immune cells called macrophages, thereby
promoting the healing of feet that were infected with a protozoan
parasite called Leishmania major.
Moving forward, the researchers will examine how salt accumulates in the
skin and triggers immune responses, and why salt accumulates in the
skin of aging adults. "A further understanding of the regulatory
cascades might not only help to design drugs that specifically enhance
local salt deposition and help to combat infectious diseases, but also
may lead to novel strategies to mobilize sodium stores in the aging
population and prevent cardiovascular disease," Jantsch says. "We also
think that local application of high-salt-containing wound dressings and
the development of other salt-boosting antimicrobial therapies might
bear therapeutic potential."
In the meantime, the researchers urge caution over the potential health
benefits of a high-salt diet. "Due to the overwhelming clinical studies
demonstrating that high dietary salt is detrimental to hypertension and
cardiovascular diseases, we feel that at present our data does not
justify recommendations on high dietary salt in the general population,"
Jantsch says. "Nevertheless, in situations where endogenous
accumulation of salt to sites of infection is insufficient,
supplementation of salt might be a therapeutic option. But this needs to
be addressed in further studies."