 Millions suffer from asthma attacks triggered by exercise. Within five minutes of starting exercising, people can get short of breath, start coughing and wheezing, such that lung function significantly drops. But on a high-salt diet, the attack is even worse. Whereas on a low-salt diet, there's hardly a significant drop in function at all. To figure out why, researchers had them all cough up sputum from their lungs, and those on the high-salt diet ended up with triple the inflammatory cells, and up to double the concentration of inflammatory mediators. But why? What does salt intake have to do with inflammation? We didn't know until now. The Western diet, high in saturated fat and salt, has long been postulated as one potential cause for the increasing incidence of autoimmune diseases in developed countries. The rapidly increasing incidence of autoimmune diseases may be due to an over-activation of immune cells called helper-17 cells. The development of multiple sclerosis, psoriasis, type 1 diabetes, chogrens, asthma, and rheumatoid arthritis have all been shown to involve this T helper-17-driven inflammation. And one trigger for the activation of those TH-17 cells may be elevated levels of salt in our bloodstream. The sodium content of processed foods and fast food can be more than 100 times higher in comparison to similar homemade meals. And sodium chloride, salt, appears to drive autoimmune disease by the induction of these disease-causing TH-17 cells. Turns out there's a salt-sensing enzyme responsible for triggering the formation of these TH-17 cells. Organ damage caused by high salt diets may also activate another type of inflammatory immune cell. A high salt diet can overwork the kidneys, starving them of oxygen-triggering inflammation. The more salt they gave people, the more activation of inflammatory monocyte cells associated with high salt intake-induced kidney oxygen deficiency. But this study only lasted two weeks. What about long-term? One of the difficulties in doing sodium experiments is it's hard to get free-living folks to maintain a specific salt intake. You can do what are called metabolic ward studies where essentially lock people in a hospital ward for a few days and control their food intake, but can't do that long-term unless you can lock people in a space capsule. Mars 520 was a 520-day space flight simulation to see how people might do on the way to Mars and back. What they found was that those on a high salt diet displayed a markedly higher number of monocytes, which are a type of immune cell you often see increased in settings of chronic inflammation and autoimmune disorders. This may reveal one of the consequences of excess salt consumption in our everyday lives, since that so-called high salt intake may actually just be the average salt intake. Furthermore, there was an increase in the levels of pro-inflammatory mediators and a decrease in the level of anti-inflammatory mediators suggesting that a high salt diet has the potential to bring about an excessive immune response, which may damage the immune balance and result in either difficulties in getting rid of inflammation or even an increased risk of autoimmune disease. What if you already have an autoimmune disease? Sodium intake is associated with increased disease activity in multiple sclerosis. If you follow MS patients for a few years, those eating more salt had 3 to 4 times the exacerbation rate, 3 times more likely to develop new MS lesions in their brains, and on average had 8 more brain lesions, 14 in their brain compared to 6 in the low salt group. So the next step is to try treating patients with salt reduction and see if they get better. But since reducing our salt intake is a healthy thing to do anyway, I don't see why anyone should have to wait.