High salt intake may not only increase the risk of heart disease, but also cause asthma, eczema and multiple sclerosis, a new study has found.
A team of scientists from Yale University in the US and the University of Erlangen-Nuremberg, in Germany, say salty diets could be partly to blame for autoimmune diseases, in which the immune system attacks healthy tissue instead of fighting pathogens.
This study is the first to indicate that excess salt intake may be one of the environmental factors driving the increased incidence of autoimmune diseases.
Markus Kleinewietfeld and David Hafler from Yale University US observed changes in CD4 positive T helper cells (Th) in humans, immune cells which were associated with specific dietary habits.
Helper T cells are alerted of imminent danger by the cytokines of other cells of the immune system.
They activate and "help" other effector cells to fight dangerous pathogens and to clear infections. A specific subset of T helper cells produces the cytokine interleukin 17 and is therefore called Th17 for short.
Evidence is mounting that Th17 cells, apart from fighting infections, play a pivotal role in the pathogenesis of autoimmune diseases.
Salt dramatically boosts the induction of aggressive Th17 immune cells.
In cell culture experiments, the researchers showed that increased sodium chloride can lead to a dramatic induction of Th17 cells in a specific cytokine milieu.
"In the presence of elevated salt concentrations this increase can be ten times higher than under usual conditions," Kleinewietfeld and Professor Dominik N Muller said in a statement.
Under the new high salt conditions, the cells undergo further changes in their cytokine profile, resulting in particularly aggressive Th17 cells.
In mice, increased dietary salt intake resulted in a more severe form of experimental autoimmune encephalomyelitis, a model for multiple sclerosis.
