While most Americans consume excessive amounts of salt, which can lead to heart disease, researchers say they've identified a previously unrecognized consequence of sodium intake that can provide a health benefit.
Consuming salt, they say, appears to be an ancient evolutionary tactic for the body to defend itself against bacteria and ward off microbes.
Research, which the scientists acknowledge is in its very early stages, suggests levels of sodium appear to increase around an infection site, inhibiting the growth and spread of bacteria.
At the site of a wound or infection, the salt strengthens the skin's antimicrobial barrier function and increases immunological defenses, they report in the journal Cell Metabolism.
The discovery was an accidental one that came about when study senior author Jens Titze of Vanderbilt University noticed that mice that had been bitten by cage companions displayed elevated levels of sodium in their skin compared to those that were wound-free.
That led Jonathan Jantsch at the University of Regensburg in Germany to wonder if the salt was involved in the infection-fighting abilities of the immune system.
Subjecting mice and human cells to elevated levels of salt in a series of experiments, Jantsch and his colleague observed immune cells being activated.
The also put some mice on high-sodium diets and others on low-sodium diets, then infected them with bacteria.
Mice on the high-sodium diet displayed stronger immune responses to the wounds caused by the bacteria and had their wounds heal faster than the mice consuming less salt, they found.
"This is a totally different view on the role of salt in health and disease," says Titze, an associate professor of Medicine and of Molecular Physiology and Biophysics at Vanderbilt.
A possible role of salt in the function of the immune system may be an evolutionary remnant from a time before antibiotics, when mammals, including humans, needed some methods of combating invading microbes, the researchers suggest.
"I really think salt is an unappreciated factor of immunity," says Jantsch.
However, with the development of effective antibiotics and other infection treatments for infection, humans may no longer need huge amounts of salt in their system to protect them, the researchers note.
"Chronic accumulation of salt in the tissue thus may have become rather a problem than an advantage," Titze says.
Therefore, the researchers caution, their findings should in no way be taken as a recommendation of a high salt diet as beneficial for health.
"I think that the most important finding here is that tissues can accumulate massive amounts of sodium locally to boost immune responses wherever needed," Titze says. "This mostly happens totally independent of the diet."