We have long been told to eat less salt as a high salt diet can lead to high blood pressure, which in turn is a risk factor for a host of health problems including heart disease and stroke. But did you know that, more recently, a high salt diet has been linked to stroke and overall brain health, regardless of the presence of high blood pressure?
It is now widely accepted that there is a connection between our minds and our guts and problems with communication between the two contribute to various diseases including Parkinson’s and IBS (irritable bowel syndrome).
This field of mind-gut connection is growing, and a 2013 study showed that high salt intake leads to significant immune changes in the gut, thereby increasing the vulnerability of the brain to autoimmunity, where the immune system attacks its own healthy cells and tissues.
A 2018 article publish in Nature Neuroscience showed a startling connection between the gut and the brain.
Immune signals from the gut have the power to compromise the brain’s blood vessels and this leads to deteriorating brain health as well as cognitive impairment. The study found that excessive salt might negatively impact brain health in humans through impairing the brain’s blood vessels. This finding was not connected to blood pressure. The researchers in this study proposed new therapeutic guidelines involving reduction in salt intake to counter stroke and cognitive dysfunction.
More specifically, as Jonathan D. Grinstein explains in Scientific American:
The researchers used mice [who were give high intakes of salt], and found that immune responses in the small intestines set off a cascade of chemical responses reaching the brain’s blood vessels, reducing blood flow to the cortex and hippocampus, two brain regions crucial for learning and memory. This, in turn, brought a decline in tests of cognitive performance. The impairment in learning and memory was clear even in the absence of high blood pressure; they observed that the gut is reacting to the salt overload and directing immune signals that lay the basis for deterioration throughout the brain’s vital vascular complex and compromise cognitive function. While this study has only been carried out on research animals so far, the scientists believe it’s likely that much of the same applies to people.
Lowering salt intake has been shown to have beneficial effects to overall health, so the researchers wanted to know whether these effects extend to this newly identified signaling cascade that begins in the gut and targets the brain’s blood vessels to, ultimately, affect cognitive function. When the mice were returned to a normal diet after being on a high salt diet, the detrimental health effects caused by excess salt intake were erased. A pharmacological intervention that disrupted the immune signals also reversed the effects.
This and other studies have implications for diseases including multiple sclerosis and rheumatoid arthritis which have a high stroke risk and poorly functioning blood vessels in the nervous system. Perhaps what is most surprising, however, is the evidence that what we eat also affects how we think. What a powerful reminder that we should not view our bodies as “pieces and parts” but rather as a whole. In this case seemingly separate parts of the body play vital roles in brain health and cognitive functioning.
The old adage “we are what we eat” certainly appears to be true.
Leslie, M. (2013, March 6). Salty food may be a culprit in autoimmune diseases. Retrieved from https://www.sciencemag.org/news/2013/03/salty-food-may-be-culprit-autoimmune-diseases
Faraco, G, Brea, D, Garcia-Bonilla, L, Wang, G, Racchumi, G, Chang, H, Buendia, I, Santisteban, MM, Segarra, SG, Koizumi, K, Sugiyama, Y, Murphy, M, Voss, H, Anrather, J, & Iadecola, C. (2018). Dietary salt promotes neurovascular and cognitive dysfunction through a gut-initiated TH17 response. Nature Neuroscience, 21: 240-249. Retrieved from https://www.nature.com/articles/s41593-017-0059-z#Sec12
Grinstein, J.D. (2018, December 5). A new connection between the gut and Brain: A surprising way that diet leads risks of stroke and cognitive impairment. Scientific American. Retrieved from https://www.scientificamerican.com/article/a-new-connection-between-the-gut-and-brain1/