Salt Is Making You Dumber. Probiotics To The Rescue.

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.

Save Your Brain. Get Moving This Year.

Let’s start the New Year by looking at the impact of physical activity and exercise on brain health and function.  Maybe if we do things right at the end of this year we will still remember what we learned in today’s article.

We all have people we care about who are getting up there in years, and getting older is something that all of us have in common.  If you are like me and see someone in their 70’s or 80’s (or older) motoring by you on a walk or grinding it out in the gym  you think “wow, I want to be like them when I’m that age” or “I wish my parents were more like that”.  Maybe you flip on the TV or read an article and come across another older adult who just blows you away with how smart and aware and engaged they are.  Is regular physical activity part of the secret to their success?  Research is starting to strongly suggest that it is.

A study by Demnitz et at. (2017) titled Associations between Mobility, Cognition and Brain Structure in Healthy Older Adults attempted to tease out the relationships between these vital elements.  Mobility was measured with gait, balance and chair-stand tests.  Cognitive measures included executive function, memory and processing-speed.  For brain structure the authors looked at grey matter volume and white matter microstructures.

All three measures of mobility had positive associations with processing speed, so if you didn’t have to reread this to follow along maybe you’ve been moving around and getting up enough.  Better executive function was correlated with faster walking speeds.  Remember that executive function relates to your ability to plan, organize and complete tasks including managing your time, staying focused and regulating emotions.  If you decided that reading this blog was important, made time for it, searched it out and are still reading your executive function may be working well.  Unfortunately none of the measures in this study were associated with improved memory.

Better mobility was also found to be associated with increased grey matter volume while a chair stand test was found to be correlated with white matter integrity.  You don’t have to be a brain scientist to understand that maintaining the volume and integrity of your brain matters.

Demnitz et al. (2016) also conducted a meta-analysis of 26 studies that explored the relationship between mobility and cognition in healthy older adults.  The authors used gait, balance and lower extremity function as the measures of mobility.  For cognition they chose global cognitive function, memory, executive function and processing speed.

With regard to gait, speed was the most commonly measured aspect and positive relationships were found between gait and all aspects of cognitive function.  This corresponds with another systematic review by Morris et al. (2016) which established meaningful relationships between gait and global cognition and executive function.

Lower extremity function was measured with either a test of how many times someone can stand up from a chair without using their arms within a given time or standing up and walking a short distance then sitting back down for time.  Again all aspects of cognitive function showed positive relationships with better lower extremity function, most notably global cognition and executive function.  While there was less data regarding balance the research that does exist points to a positive relationship.

A meta-analysis by Santos-Lozano et al. (2016) found a 40% reduction in risk of developing Alzheimer disease for those that engaged in moderate to vigorous physical activity compared to those who were sedentary.  Tan et at. (2016) found relationships between higher levels of physical activity and brain volume as well an increased risk for dementia for those in the lowest quintile of physical activity as compared to those in the highest.

Want more evidence that physical activity helps preserve brain volume?  A study of 1449 middle-aged adults by Rovio et al. (2010) found that those who engaged in physical activity in midlife showed greater grey matter volume when measured 21 years later as opposed to those who where more sedentary.  In a study of 299 adults, Erickson et al. (2010) found that increased physical activity in the form of walking positively correlated with increased grey matter volume 9 years later and that increased grey matter volume reduced the risk of cognitive impairment by 2-fold.  Bugg and Head (2009) also found that subjects who engaged in more physical activity had higher frontal region brain volumes and that age-related atrophy of the medial temporal lobe was significantly reduced compared to those who engaged in low levels of physical activity.  There are so many studies showing a relationship between physical activity and neuro-protective effects that to type all of them out would almost give me a day’s worth of brain preservation.  (For those of you not regularly exercising and suffering brain atrophy that is a joke, you can not consider typing on your computer physical activity. I’m limiting how many examples I give so as not to bore you to death and so I can get up and move instead.)

As always we must remember there are limitations to all of these studies and we must be careful not to over-interpret any of the results.  Among the factors that can impact the studies are issues regarding which tests are conducted, how the results are measured, how appropriate those test and measurements are to get the ultimate question of what relationship exists between the variables in question, the number of subjects, gender, age, health and to what extent cognitive issues led to the decline in mobility as opposed to increased or decreased mobility impacting cognition.  All of that being said, there are enough studies available to strongly suggest that a relationship between mobility and cognitive function does exist.  We only reviewed a small sample of the research in this area.

Now what does all of this mean for today’s strength/conditioning/fitness professional working with older adults or just the average person reading this who is concerned about their future brain function?  Certainly we can impact lower extremity function by training lower body and core strength.

Improving squat, deadlift, lunge and step-up patterns in terms of neurological control/coordination as well as basic strength will certainly have carry over effects to overall lower body function.  You don’t have to put a barbell on someone’s back or move heavy weight to significantly impact lower extremity strength in older and untrained individuals.  Body weight and light weights will have plenty of impact.  Yes we are always thinking of improvement but you need to take into account the realities of the person in question.  Very slow and small changes add up over time if you can establish consistency.  And let’s face it; consistency is often the number one battle.

Perhaps you or your client has injuries or significant limitations in function.  That only makes this all the more important.  Yes you might have to change the exercises but there are plenty of work-arounds.  If a back or knee injury limits squat and deadlift patterns to no more than body weight or with limited range of motion those body weight movements still matter and you can supplement them with other exercises such as sled pushes which require tremendous hip drive.  While I don’t rely on machines that often they can still be useful and shouldn’t be forgotten.  That leg extension or seated leg curl may have a place in a program.

As for improving gait there may be basic foot strike patters such as walking through the big toe that need to be addressed but more than anything the key to better gait, including improvements in speed and cardio-respiratory fitness for older adults is walking more.  No equipment necessary besides a good pair of sneakers.

So there you have it.  Just a tiny sampling of the research on brain health and movement.  One more reason to get up from the computer or off the sofa and take a walk or do a few sets of squats.

Bugg, J. and Head, D. (2011) Exercise moderates age-related atrophy of the medial temporal lobe. Neurobiology of aging. March, 32(3): 506-514.

Demnitz, N., Esser P., Dawes, H., Valkanova, V., Johansen-Berg, H., Ebmeier, KP. and Sexton, C.  (2016) A systematic rewiew and meta-analysis of cross-sectional studies examining the relationship between mobility and cognition in healthy older adults.  Gait Posture, Oct, 50:164-174. 

Demnitz, N., Zsoldos, E., Mahmood, A., Mackay, CE., Kivimaki, M., Singh-Manoux, A., Dawes, H., Johansen-Berg, H., Ebmeier, KP. and Sexton, CE.  (2017)  Associations between Mobility, Cognition and Brain Structure in Healthy Older Adults, Front. Aging Neurosci.,  May 23,  

Erickson, K.I., Raji, C.A., Lopez, O.L., Becker, J.T., Rosano, C., Newman, A.B., Gach, H.M., Thompson, P.M., Ho, A.J. and Kuller, L.H. (2010) Physical activity predicts grey matter volume in late adulthood. Neurology, Oct, 75(16):1415-1422

Morris, R., Lord, S., Bunce, J., Burn, D. and Rochester, L. (2016) Gait and cognition: Mapping the global and discrete relationships in ageing and neurodegenerative disease. Neurosci Biobehav Rev., May, 64:326-45.

Santos-Lozano, A., Pareja-Galeano, H., Sanchis-Gormar, F., Quindos-Rubial, M., Fiuza-Luces, C., Cristi-Montero, C., Emanuele, E., Garatachea, N. and Lucia, A. (2016) Physical Activity and Alzheimer Disease: A Protective Association. Mayo Clinic Proceedings, August 91(8): 999-1020.

Rovio, S., Spulber, G., Nieminen, LJ., Niskanen, E., Winblad, B., Tuomilehto, J., Nissinen, A., Soininen, H. and Kivipelto, M. (2010) The effect of midlife physical activity on structural brain changes in the elderly. Neurobiol Aging, Nov, 31(11):1927-1936.

Tan, ZS., Spartano, NL., Beiser, AS., DeCarli, C., Auebach, SH., Vasan RS. and Seshardi, S. (2017) Physical Activity, Brain Volume, and Dementia Risk: The Framingham Study.  J Gerontol A Biol Sci Med Sci. June 1, 72(6):789-795.