Even Minor Head Injuries Affect Your Microbiome
Every time you hit your head, you disturb your gut microbes.
Posted May 18, 2026 | Reviewed by Kaja Perina
“It has been said, time heals all wounds. I do not agree. The wounds remain. In time the mind, protecting its sanity, covers them in scar tissue and the pain lessens, but it is never gone” —Rose Kennedy
It seems we’re all pounding our heads against a crazy world these days, but for some people it’s more literal. Hitting your head can give you anything from a little bump to a cracked skull, and it’s surprisingly common. Some 2 million people suffer a traumatic brain injury every year. Over 5 million Americans are living with permanent cognitive and physical disabilities from head trauma.
Some of those people might have had a better outcome with newer therapies. Amazingly, those breakthrough treatments don’t work directly on the brain, but on the gut. You might not be surprised that they make use of the gut-brain axis . We mostly think about how gut microbes affect the brain, but it goes both ways.
The story starts with a deep dive into our evolutionary past. Our bodies were pretty much assembled and tested millions of years ago, when a blow to the head was either lethal or alarming. In situations like that, our flight-or-fight mechanism kicks in. If we wanted to survive a blow from a club-wielding troglodyte, we had to quickly summon up our inner Conan.
That meant that all our blood was sent to our muscles to fight or get the hell out of there. Whatever wounds we suffered were better attended to without letting our adversary pile on.
That makes a lot of sense, as long as the stress doesn’t last too long. But head injuries often linger, and all that blood in your muscles means there isn’t much left for our gut.
The gut understandably plays second-fiddle here, but at a cost. With our gut lining starved for blood, intestinal function starts to shut down.
Special cells in your gut that spin out antimicrobials start to flag and die out. That gives pathogens carte blanche to attack the gut lining. The victory of these pathogens comes at the expense of beneficial bacteria that produce butyrate, an important molecule that both nourishes and heals the cells lining the gut.
The lining itself, pale with anemia, loses its integrity. That allows the ascendant pathogens to break through, entering the bloodstream. Soon your microbiome looks completely different, and you have microbes and toxins being pumped full blast to every organ in your body.
This is the price you pay when you face lethal danger every day. It’s a Faustian trade-off, sacrificing your gut to save your butt.
In fact, almost every person with traumatic brain injury gets an unbalanced gut — called dysbiosis — within 24 hours of their injury. Three quarters will be even worse off, with a notable breakdown of the gut lining. This is no longer a localized head injury, and can lead to systemic sepsis, explaining why brain trauma survivors have 3-10 times greater odds of dying than those without head injury.
As you recuperate, your blood returns to your gut, but there will likely be a long-term alteration of your gut microbiome. Surprisingly, these gut changes can happen with even minor impacts that don’t cause a concussion. Studies with college football players show a drop in beneficial bacteria within hours of a hit.
American footballers often use their head as a battering ram, and pretty much every one of them has some kind of brain injury. Neuropathologist Bennet Omalu, a pioneering researcher on chronic traumatic encephalopathy , says, “All the NFL players I have examined pathologically, I have not seen one that did not have brain damage.”
From there, if the trauma doesn’t resolve quickly, chronic systemic inflammation can start to fester, leading to a rogue’s gallery of intractable diseases, from dementia and Parkinson’s to heart disease and arthritis. If the gut isn’t addressed, a vicious cycle sets in, with the gut inflaming the brain, and the brain returning the favor.
This chain of grief can taint the rest of your life. Lingering brain damage can lead to violent behavior, substance abuse , and mental problems. Astonishingly, almost 50% of prisoners have a history of traumatic brain injury.
Hospital protocols now include tube feeding within 24 hours of an injury to normalize the gut. The doctors concoct a blended soup of nutrients called an immunonutrition formula, containing a suite of substances to treat the gut dysbiosis.
Two amino acids are important: glutamine and arginine. Glutamine, along with butyrate, is a primary food for the cells lining the gut, and helps to glue them together for a tight seal. Arginine helps to repair ulcers and replenish the mucus lining.
Omega-3 oils are anti-inflammatory, both in the gut and the brain. Another key ingredient is fiber, in the form of prebiotics — aka food for probiotic bacteria. These include guar, pectin, or indigestible chains of sugar called oligo-saccharides. These feed the butyrate-producing microbes that help to heal the gut.
Prebiotics will encourage the growth of your homegrown probiotics. But you can speed things up by adding the appropriate probiotics directly, including Clostridium butyricum, Lactobacillus reuteri, Bifidobacterium longum , Lactobacillus bulgaricus , and Streptococcus thermophilus . The alert reader will recognize some of these as denizens of yogurt.
So, intriguingly, the first-line therapy for brain injury is gut restoration.
You don’t need to stop eating fiber after you get your feeding tube out. A good Mediterranean-style diet can keep the goodness coming, hopefully putting an end to the downward spiral of untreated brain injury.
Another thing to do is re-examine your sports to minimize head trauma. Now that you know even mild hits can have a lasting effect, you might want to abandon football and take up something like badminton. It may be a smarter way to keep your head in the game.
El Baassiri, Mahmoud G., Zachariah Raouf, Sarah Badin, Alejandro Escobosa, Chhinder P. Sodhi, and Isam W. Nasr. “Dysregulated Brain-Gut Axis in the Setting of Traumatic Brain Injury: Review of Mechanisms and Anti-Inflammatory Pharmacotherapies.” Journal of Neuroinflammation 21, no. 1 (2024): 124.
Pelland, Zachary J., Aziz Zafar, Ahmet A. Ay, and Kenneth Douglas Belanger. “Non-Concussive Head Impacts Sustained during American Football Correlate with Changes in Gut Microbiome Diversity and Composition.” PLOS ONE 21, no. 5 (2026): e0345651.
Soriano, Sirena, Kristen Curry, Saeed S. Sadrameli, et al. “Alterations to the Gut Microbiome after Sport-Related Concussion in a Collegiate Football Players Cohort: A Pilot Study.” Brain, Behavior, & Immunity - Health 21 (May 2022): 100438.
Lin, Yongshuang, Chengshan Hou, Cheng Wang, et al. “Research Progress on Digestive Disorders Following Traumatic Brain Injury.” Frontiers in Immunology 15 (December 2024): 1524495.
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Scott C. Anderson is a science journalist and coauthor with John Cryan and Ted Dinan of "The Psychobiotic Revolution" from National Geographic.
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This article is part of the Bringwise Psychology Journal — daily insights on human behavior, mental health, and personal growth.