Autoimmune diseases linked to a diet high in salt
7th March 2013
saltScientists claim that the typical modern day diet that is high in salt could be a key factor behind recent increases in the cases of autoimmune diseases such as multiple sclerosis, lupus, alopecia, asthma and eczema. An autoimmune disease occurs after the immune system attacks healthy body cells instead of fighting off disease and infection as it should be doing. An autoimmune disease can drastically vary in the severity of symptoms – sometimes flaring up and other times they can go into remission and disappear for some time. Initial symptoms are usually fatigue, muscle aches and a low fever. A usual indicator of an autoimmune disease is inflammation, resulting in redness, heat, pain and swelling. The treatment for an autoimmune disease will depend on the specific disease but usually the main aim is to reduce inflammation. A common autoimmune disease is the neurological condition multiple sclerosis, which affects around 100,000 people around the UK. It develops after a protein surrounding the brain and spinal cord (myelin) becomes damaged following a breakdown in the immune system. This disrupts nerve signals from the brain to the rest of the body resulting in loss of vision, muscle stiffness and uncontrollable movement, fatigue and ataxia (balance and coordination problems). Reporting their data in the journal Nature, scientists from Yale University in the U.S. and the University of Erlangen-Nuremberg, in Germany, say that they believe salt consumption could be connected to rising rates in autoimmune diseases. Previously many health experts have stated that genetics increase the risk of such diseases in addition to our surrounding environment. Other reasons for the progression of multiple sclerosis are from a viral infection, smoking and a lack of vitamin D. In their report, the researchers note: “This study is the first to indicate that excess salt may be one of the environmental factors driving the increased incidence of autoimmune diseases.” For their study, the team decided to focus on the presence of T helper cells in the body. T helpers are a sub-group of lymphocytes that work to help other cells fight viruses or bacteria by releasing T cell cytokines. A subset of these T helper cells are known as ‘Th17 cells’ and past researcher has suggested that the Th17 cells help to promote inflammation that is important for defending against pathogens, and connected to diseases like multiple sclerosis, psoriasis, and rheumatoid arthritis. Treatment options for some of these diseases involve manipulating T cell function. Vijay Kuchroo of the Harvard-affiliated Brigham and Women's Hospital and a member of the Broad Institute, says: “The question we wanted to pursue was: How does this highly pathogenic, pro-inflammatory T cell develop. Once we have a more nuanced understanding of the development of the pathogenic Th17 cells, we may be able to pursue ways to regulate them or their function.” The scientists found that by exposing the Th17 cells to a salt solution made them act more ‘aggressively’. In addition, it was discovered that adding salt to the diet of mice actually increased the number Th17 cells and that genetically engineered mice with a form of MS, suffered with more severe MS disease in comparison to those mice fed a more ‘normal’ diet. Study co-author Ralf Linker, from the University of Erlangen-Nuremberg, said: “These findings are an important contribution to the understanding of multiple sclerosis and may offer new targets for a better treatment of the disease, for which at present there is no cure.” Another of the study's authors, Professor David Hafler, from Yale University, added: “These are not diseases of bad genes alone or diseases caused by the environment, but diseases of a bad interaction between genes and the environment. Humans were genetically selected for conditions in sub-Saharan Africa, where there was no salt. Today, Western diets all have high salt content and that has led to increase in hypertension and perhaps autoimmune disease as well.”