Article by Dr. Micah Yu 

Autoimmunity has increased in many western countries in the past decade. The typical “Western diet” includes high protein, high salt, and high sugar and this helps promote obesity and metabolic syndrome. Genetic and environmental factors play a role in the development in autoimmunity. However, because our genetics as a human species has not changed much in the past century, we have to look towards the environment as the culprit to the rising incidence of these diseases. Salt is one of the factors we have to consider when we think of potential underlying culprits to autoimmunity. Salt is a necessary nutrient but excess salt intake is not.(1) The World Health Orgnaization(WHO) recommends limiting salt intake to less than 5 grams per day in order to reduce the risk of hypertension and kidney disease.(2) In some parts of the world, salt intake is less than 1gram per day while in the Western world, it can be more than 20 grams per day.(3) Worldwide, the mean daily salt intake is 9 to 12 grams. Excessive salt has demonstrated that it favors a pro inflammatory response. This has been shown in rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis, and inflammatory bowel disease.

If you have autoimmune disease you have to be very careful of excess salt. Salting to taste at home should be okay but once you are eating out the salt level can be way too high. Excess salt can increase your inflammatory T cells which include your T helper 17 cells. Your T helper 17 cells then send inflammatory signals throughout the rest of your body. Your regulatory T cells(Treg) balance out the inflammatory T helper 17 cells, which prevents the inflammatory T cells from creating more inflammation in the body. However, salt can reverse the anti inflammatory effects of the regulatory T cells, thus creating more inflammation in the body. This increase in inflammation can be associated with flares of an autoimmune disease, particularly in rheumatic autoimmune disease.

Studies:
This has been studied in both animal models as well as humans. When it comes to the basic science, it has been shown that high concentration of sodium(NaCl) promote differentiation of T helper cells towards the proinflammatory Th17 immune cells through SGK1(serum and glucocorticoid induced kinase 1). This in turn can stimulate Th17 to create the interleukin 17 and TNF, which are both pro inflammatory cytokines. Cytokines are small proteins used for cell to cell communication. In rheumatic diseases, it was shown that the pro inflammatory Thelper 17 cells from rheumatoid arthritis and osteoarthritis patients increased with increasing amount of sodium. (7) An observational study was done to see if there was a correlation with salt intake and multiple sclerosis. Patients gave urine samples to assess sodium intake. What they found was that there was a positive correlation between exacerbation rates and sodium intake. Interestingly, there was a 2.75 fold for patients with medium sodium intake and 3.95 fold in the high sodium intake group.(4)

A study was done on healthy humans in which a high sodium diet was given. The participants were either given 12 grams of salt per day or 6 grams of salt. Blood samples were taken of the participants of their immune cells. What it showed was that the participants with high salt diet had a higher number of monocytes(a certain group of white blood cells) compared to the low salt group. When the group that was taking a higher salt diet switched to a lower salt diet, there was a reduction in proinflammatory cytokines interleukin 6 and interleukin 23 along with increased production of the anti inflammatory cytokine interleukin 10.(5) 

In general, a high salt intake is not recommended, even for people without autoimmune diseases. Your kidneys are responsible for filtering out salt in the blood after it is absorbed from your digestive system. Excess salt can overload your kidneys. As a result, your body will attempt to retain water in order to dilute the salt. However, this will increase the amount of fluid in your body and the volume of the blood. This increased blood volume will result in your heart having to work harder, just like your kidneys. This strain on your heart and blood vessels can lead to high blood pressure, heart attack, heart failure, and stroke. There are some times when an increase in salt in the diet is recommended, but this is not common. Cardiologists may recommend a slight increase in salt for a patient with drastically low blood pressure or POTS (postural orthostatic tachycardia syndrome), but this is on a case-by-case basis. In general, you should always limit your salt intake to ensure you are not creating extra work on your kidneys, heart, and blood vessels.

Gut Microbiome:
The gut microbiome is so important to the immune system. Studies on mice have shown that a high salt diet is associated with a negative effect on the gut biome. A high salt intake has been shown to reduce the Lactobacillus colonies, which is a healthy gut bacteria. Studies in mice have shown that Lactobacillus supplementation blunted the effects of a high salt diet inducing inflammatory T cell activation.(6) Some prebiotic foods that can help with increasing lactobacillus is miso paste, tempeh, and kimchi.

Conclusion:
Salt is a necessary nutrient in our body. However, in the current standard american diet, the amount of salt ingested is way too high. Salt can potentially cause autoimmune flares and increase risk of autoimmune disease. If you are flaring then it’s best to be mindful of your salt intake even more. When I eat too much salt I feel the difference in my body. When I go eat out I try to be mindful of my salt intake. You can always ask for the food you order to have no salt or minimal salt. We need more research to be done on salt and autoimmunity but the research is pointing to excess salt being an implication of disease.

Tip: Ask your server to not salt the food when you eat out. If you need salt then salt the food yourself so you can control it. Often times we don’t need salt when eating food since the spices have so much flavor already.

References:

1. Sigaux, Johanna, Luca Semerano, Guillaume Favre, Natacha Bessis, and Marie-Christophe Boissier. “Salt, Inflammatory Joint Disease, and Autoimmunity.” Joint Bone Spine 85, no. 4 (July 1, 2018): 411–16.

2. World Health Organization. Sodium intake for adults and children – Guideline; World Health Organization: Geneva, Switzerland, 2012.

3.. Manzel A. Role of “Western Diet” in Inflammatory Autoimmune Diseases. Curr Allergy Asthma Rep. 2014 January ; 14(1): 404.

4. Farez, Mauricio F., Marcela P. Fiol, María I. Gaitán, Francisco J. Quintana, and Jorge Correale. “Sodium Intake Is Associated with Increased Disease Activity in Multiple Sclerosis.” Journal of Neurology, Neurosurgery, and Psychiatry 86, no. 1 (January 2015): 26–31.

5. Yi, B.; Titze, J.; Rykova, M.; Feuerecker, M.; Vassilieva, G.; Nichiporuk, I.; Schelling, G.; Morukov, B.;Choukèr, A. Effects of dietary salt levels on monocytic cells and immune responses in healthy human subjects:a longitudinal study. Transl. Res. 2015, 166, 103–110.

6. Wilck, Nicola, Mariana G. Matus, Sean M. Kearney, Scott W. Olesen, Kristoffer Forslund, Hendrik Bartolomaeus, Stefanie Haase, et al. “Salt-Responsive Gut Commensal Modulates T H 17 Axis and Disease.” Nature 551, no. 7682 (November 2017): 585–89. https://doi.org/10.1038/nature24628.

7. Jung, S.M.; Kim, Y.; Kim, J.; Jung, H.; Yi, H.; Rim, Y.A.; Park, N.; Kwok, S.K.; Park, S.-H.; Ju, J.H. Sodium chloride aggravates arthritis via Th17 polarization. Yonsei Med. J. 2019, 60, 88–97.

8. Meer, Jos W. M. van der, and Mihai G. Netea. “A Salty Taste to Autoimmunity.” The New England Journal of Medicine 368, no. 26 (June 27, 2013): 2520–21.

9. Salt and Sodium. Harvard T Chan School of Public Health. https://www.hsph.harvard.edu/nutritionsource/salt-and-sodium/#:~:text=Salt%2C%20also%20known%20as%20sodium,a%20high%20amount%20of%20salt