Mice and men: Again no connection

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For quite a while, ACSH has been skeptical to say the least about the scientific basis of the prevailing guidelines and studies about salt and salt intake, and here s another one to add to the list: Too much salt may trigger autoimmune diseases.

Three studies published online this week in Nature suggest that the salt we eat may influence the balance of a healthy immune system and indirectly encourage overproduction of certain immune cells. The studies focused on the development of a group of immune cells known as T cells cells that play a role in clearing disease-causing pathogens and also may promote the development of autoimmune diseases. The particular disease studied in these articles was multiple sclerosis in mice.

Senior study author Dr. David Hafler of Yale School of Medicine explained that an accidental discovery that people who ate at fast food restaurants more than twice per week seemed to have higher levels of inflammatory cells than others sparked the researchers interest. Using mice that had been bred to develop multiple sclerosis, Dr. Hafler and his team found that feeding them a high-salt diet caused the rodents to produce a type of immune-mediating cell that is closely associated with autoimmune diseases. The mice on high salt diets developed a severe form of multiple sclerosis, called autoimmune encephalomyelitis.

Dr. Hafler s study is one of three papers, published in Nature, that show how salt may overstimulate the immune system. In addition to Hafler's research, scientists from the Broad Institute in Boston explored how genes regulate the immune response, and researchers from Harvard Medical School and Brigham and Women's Hospital in Boston zeroed in on how autoimmunity is controlled by a network of genes.

The fact that this is a mouse study needs to be highlighted, says ACSH s Dr. Gilbert Ross. While the authors noted that the findings from animal studies are not always mirrored in human trials, I d go quite a bit farther than that and say that the mouse immune system is hardly analogous to that of humans. He continues, Moreover, these particular mice were bred to uniformly develop MS, making them yet more inappropriate as human immunological analogs. And just what does high salt for mice mean for us? If there was any cause for extrapolation, wouldn t the activity of illnesses among those with MS and other autoimmune diseases, such as lupus and type-1 diabetes, have been noted to be salt-sensitive? I think the breathless, near hysterical press coverage of these studies is entirely unwarranted.