We have all recently seen a lot of information released regarding the connection between the gut and other aspects of our health. Now we have one more that shows a significant connection between salt consumption, our gut and our intelligence. Yes that’s right. The impact of salt on your gut may be making you dumber as read this so hurry up and finish this article before you eat all of those chips.
A recent study published in Nature Neuroscience (Faraco et al. 2018) found that a high salt diet in mice led to reduced blood flow to the brain, damage to blood vessels in the brain and lower scores on tests of cognitive function. What was most interesting about these findings was they were not the result of increases in blood pressure due to a high sodium diet but due to an immune system reaction that occurred because of the action of the salt in the gut.
The mice fed a high salt diet had an immune reaction in their small intestines where TH17 cells are stimulated resulting in the release of a substance called interlukin-17 (IL-17). The IL-17 is an inflammatory substance that sets off a reaction that results in damage to the inner lining of small blood vessels in the brain. This led to a decrease in blood flow to areas of the brain strongly involved in learning and memory which in turn led to measurable cognitive declines. When the high salt diets were stopped the mental performance of the mice returned to previous levels.
Yes you are sitting there saying “this was in mice, I’m a human”. Very true, or you are the smartest mouse ever working the internet and reading this article. However the physiology of mice and the reactions they have is very similar to humans and that is why they are so commonly used in early studies. While we cannot say conclusively the exact same reaction will happen in humans, researchers strongly suspect it will.
So there you have it, one more very scary reason to cut back your sodium intake. Unless you are so addicted to the salt lick that you can no longer comprehend what you just read and the danger that high sodium intakes have.
Probiotics To The Rescue
Those tricky TH17 cells don’t only appear to have impacts on the brain through non-blood pressure related mechanisms, they also stimulate inflammatory processes that lead to increases in blood pressure. So essentially it sounds like they are trying to get you no matter what through multiple pathways. And in a way they are but there is hope and it looks like those Whole Foods loving, health food store advocates have had the answer all along, probiotics.
A study published this past November (Wilck et. at. 2017) fed our old mice friends a high salt diet and watched as the number of TH-17 cells increased in response. Along with that there was a significant decrease in a type of gut bacteria called Lactobacillus murinus and to no one’s surprise, blood pressure went up.
When the subjects were given a probiotic with Lactobacillus murinus they experienced a reduction in both TH-17 cells and blood pressure. Score one for the probiotics.
A small study with human subjects was then done where the subjects were given a high sodium intake for two weeks. They experienced a reduction in their lactobacillus counts while there was an increase in the number of TH-17 cells and blood pressure.
When subjects were given a probiotic for a week before the high salt diet began their lactobacillus levels and blood pressure remained normal while on the high salt diet. Score two for probiotics.
So once again we are a seeing links between the gut microbiome and our health along with more evidence that high salt intake is a bad for us.
This isn’t the first time that probiotics have been suggested to lower blood pressure. If we step into the way back machine a meta-analysis conducted in 2014 by Khalesi et al. found a positive effect of probiotic consumption. The study suggested that the effect was greatest on individuals who already had high blood pressure, consumed a probiotic with multiple species, took them for greater than 8 weeks and at higher doses, greater then 1011.
Keep an eye out for upcoming articles about the microbiome, how it impacts our health and what we can do to optimize it.
Faraco, G., Brea, D., Garcia-Bonilla, L., Wang, G., Racchumi G., Chang, H., Buendia, I., Santisteban, M., Segarra, S., Koizumi, K., Sugiyama, Y., Murphy, M., Voss, H., Anrather, J. and Iadecola, C. (2018) Dietary salt promotes neurovascular and cognitive dysfunction through a gut-initiated TH17 response. Nat Neuroscience: Jan 15 (epub). Khalesi, S., Sun, J., Buys, N. and Jayasinghe, R. (2014) Effect of probiotics on blood pressure: a systematic review and meta-analysis of randomized, controlled trials. Hypertension: Oct; 64(4):897-903. Wilck et at. (2017) Salt-responsive gut commensal modulates TH17 axis and disease. Nature: Nov 30; 551(7682):585-589.