It's mantra we have known for decades: too much salt is bad for you. We know the consequences of not adhering to this simple rule are vast including a higher risk for cardiovascular disease, stroke and even the condition where our bodies harm themselves, autoimmunity. It should come as no surprise the government has developed guidelines for salt intake and food manufacturing companies have worked to appease those watching their sodium levels by releasing a plethora of products all claiming to be low-salt.
While most health proponents work hard to reduce our salt intake, when it comes to preventing and resolving infections, higher salt may be better. Although the concept may create headaches for dietitians and public health officials, a study published last week suggested there may be reason to seek more sodium. According to the team of researchers, higher amounts of sodium (one of the two elements found in salt) in the diet may help to fight off skin infections. The results could translate into dietary changes to help prevent unwanted microbial dermal invasions.
The study aimed to show higher levels of sodium could increase the skin's defense against one particular pathogen, Leishmania major. For most Canadians, this pathogen is not of any concern. But to many parts of the world, the infection is a significant problem leading to some 1.3 million infections and between 20 and 30 thousand deaths each year.
Using a modified form of magnetic resonance imaging (MRI), they found what they expected. Infected individuals had higher levels of sodium in their skin. This gave them the evidence they needed to investigate the role of sodium further although they would have to change their subjects to another animal: the mouse.
First, the mice were given either a low salt or a high salt diet for two weeks to establish their sodium levels. Then, they were infected with the pathogen to see what would happen. Though the researchers expected to see some difference, the results were dramatic. Low salt mice simply could not rid themselves of the infection. Those on a high salt diet, however, somehow managed to get better. When the researchers began to investigate the difference, they found the shift had to do with a change in the immunity of the animal. But this was not widespread as only one type of cell seemed to be affected.
The cell is called a macrophage, and it has many roles in the body. One of its primary functions is as a part of the first line of defense against pathogens. Near the surface of the skin, this cell continuously monitors for any signs of infection or injury. If anything is detected, they work hard and fast to remediate the problem and even heal the wound.
When macrophages are exposed to higher concentrations of sodium, like a moth to a flame, they tend to move towards the area. This movement is known as chemotaxis and it is involved in helping to identify a hurt area. In the skin, when injury occurs and cells die, salt is released and migrates down towards the bloodstream. Eventually, the macrophage will pick up the signal and head to the trouble zone. If there is a pathogen present, the defense mechanism is turned on. If it is just an injury, the wound healer takes over.
In the context of the experiment, the authors suggested the higher salt diet led to the release of a higher amount of sodium in the environment. This led to a stronger chemical signal to the macrophages and a response robust enough to combat the infection. In a lower salt diet, the signal would be weaker and as such not attract as many macrophages. In turn, the infection could continue without end.
Based on the study, one might believe a higher salt diet may be worthwhile if at least to stop Leishmania. But before you reach for the salt shaker, there is one other aspect to higher salt concentrations worth noting. While a macrophage's taste for sodium may help on the skin, in the rest of the body, there may be troubles.
One of the most problematic concerns with high sodium intake is autoimmunity in which the immune system attacks our own bodies. Higher sodium chloride is a key indicator for the development of this condition. A rise in sodium based immune function can also lead to inflammation which in turns leads to higher blood pressure and hypertension. Finally, the higher salt levels may contribute to a higher level of inflammation in the kidneys and may possibly shorten their lifespan.
The results of the study do have some value in determining directions for prevention and treatment of Leishmania infection with sodium. The data also help us understand the role of salt in fighting an infection. Both of these revelations may lead to short-term treatments over time. But for the rest of us who are not at risk, when it comes to whether or not we should be eating more salt to keep infections at bay, the answer is thankfully, no.
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