Why Your Stomach Suffers After a Traumatic Brain Injury?

TBI, Gut Health, and the Vagus Nerve: Restoring Brain–Gut Balance

 

After a traumatic brain injury (TBI), most people expect headaches, brain fog, or balance problems. Fewer people realize that the stomach and intestines can suffer just as much as the brain. Many patients notice nausea, constipation, diarrhea, food sensitivities, or a “nervous stomach” that just will not settle down after their head injury. Over time, these gut problems can feed back into the brain, making recovery slower and more frustrating (Fong, 2024; Flint Rehab, 2025). (cognitivefxusa.com)

This article explains, in plain language, how TBI can damage the brain–gut axis, trigger “leaky gut,” and change the gut microbiome. It also explains how integrative chiropractic care, especially when combined with functional medicine and neurology, can help calm the nervous system, support vagal tone, and improve communication between the brain and gut—potentially easing digestive symptoms and supporting healing.

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The Brain–Gut Axis: How the Brain Talks to the Stomach

The brain and gut are constantly communicating with each other. This two-way communication system is known as the brain–gut axis (sometimes referred to as the “microbiota–gut–brain axis”). It includes:

• The vagus nerve, which sends calming “rest and digest” signals
• The enteric nervous system (ENS), often called the “second brain” in the gut
• The immune system, which reacts to threats in the intestines
• The gut microbiome, the trillions of bacteria and other microbes living in the gut

This axis enables the brain to control digestion and allows the gut to send signals back that influence mood, pain, sleep, and even thinking (Hanscom et al., 2021; Krakovski et al., 2022). (PubMed)

A healthy brain–gut axis helps:

• Move food smoothly through the GI tract
• Maintain a strong gut lining that keeps toxins out of the bloodstream
• Support a balanced community of gut bacteria
• Regulate inflammation and immune activity

When a TBI occurs, this delicate system can move out of balance in several ways.

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How Traumatic Brain Injury Disrupts the Gut

1. TBI Can Trigger “Leaky Gut” (Increased Intestinal Permeability)

After a TBI, inflammatory signals from the injured brain can “spill over” into the rest of the body, including the intestines. Research indicates that brain injury can lead to increased intestinal permeability, often referred to as “leaky gut,” where the gut wall becomes more porous and less effective at keeping out harmful substances (Albert, 2025; Rice et al., 2019). (Thieme)

When this barrier is weakened:

• Bacterial fragments (such as endotoxin/LPS) can leak into the bloodstream
• Immune cells react strongly and release inflammatory chemicals
• Systemic inflammation rises and can worsen brain inflammation and damage

Reviews of TBI and gut health consistently report that increased gut permeability is part of the secondary injury process—the wave of damage that continues long after the initial hit to the head (Hanscom et al., 2021; Marshall & Murphy, 2022). (PubMed)

2. TBI Causes Gut Microbiome Changes (Dysbiosis)

The gut microbiome refers to the community of bacteria, viruses, and fungi that reside in the intestines. A balanced microbiome helps with digestion, vitamin production, immune function, and even brain health.

After TBI, animal and human studies show:

• Microbiome changes can appear within hours to days after injury
• Helpful species may decrease, while more inflammatory species increase
• These shifts (called dysbiosis) are linked to worse neurocognitive outcomes and more inflammation (Zhu et al., 2018; Davis et al., 2021; Rice et al., 2019). (PMC)

One review notes that TBI-related dysbiosis and the resulting leaky gut can change the way the immune system and brain respond, further increasing neuroinflammation and brain damage (Krakovski et al., 2022). (PMC)

3. Damage to the Autonomic and Enteric Nervous Systems

The autonomic nervous system (ANS) regulates automatic functions, such as heart rate, blood pressure, and digestion. The enteric nervous system (ENS) is the local nerve network lining the gut.

Head injuries can disturb both systems, especially if there is damage to the brainstem or vagus nerve. This leads to a condition called dysautonomia, where the balance between “fight-or-flight” (sympathetic) and “rest-and-digest” (parasympathetic) is disturbed (Fong, 2024; Hanscom et al., 2021). (cognitivefxusa.com)

As a result:

• Gut motility can slow down, causing constipation and bloating
• In other patients, motility speeds up and leads to diarrhea
• The coordination of muscular contractions (peristalsis) can become irregular, making it harder for food to move through the intestine (Ghaemi, 2025). (ScienceDirect)

TBI-related dysautonomia also weakens the “brake” of the vagus nerve, which normally helps calm inflammation in the gut and other organs.

4. Medicines and Stress Add to Gut Problems

Many people with TBI take pain medicines, muscle relaxers, anti-nausea drugs, sleep aids, or antibiotics. These can:

• Slow down gut motility
• Irritate the stomach lining
• Change the balance of gut bacteria

At the same time, stress, poor sleep, and reduced physical activity after an injury can further disturb gut function and microbiome balance (Flint Rehab, 2025; Fong, 2024). (Flint Rehab)

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Digestive Symptoms After Concussion and TBI

Because of all these changes, many people experience stomach and bowel symptoms after a head injury. Common complaints include:

• Nausea and vomiting
• Loss of appetite or early fullness
• Constipation or diarrhea
• Bloating, gas, and abdominal discomfort
• Acid reflux or heartburn
• Food sensitivities or new intolerances
• Unwanted weight loss or weight gain

Clinical centers focused on concussion care report that these symptoms may appear soon after injury or develop months later, especially in patients with post-concussion syndrome (Fong, 2024). (cognitivefxusa.com)

Sadly, many patients are told that their gut problems are “unrelated” to the head injury. Newer research on the brain–gut axis now confirms that TBI can directly cause GI dysfunction, and these gut symptoms deserve attention in the recovery plan (Hanscom et al., 2021; El Baassiri et al., 2024). (PubMed)

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How Gut Problems Can Make Brain Injury Worse

The relationship between the brain and the gut is a two-way street. Gut problems do not just sit in the abdomen—they can feed back and worsen brain symptoms.

1. Systemic Inflammation and Secondary Brain Injury

When the gut becomes leaky, bacteria and toxins can cross into the bloodstream, triggering immune responses. This can:

• Raise levels of inflammatory cytokines and reactive oxygen species
• Activate immune cells in the brain
• Increase microglial activation and neuroinflammation

Reviews on the microbiota–gut–brain axis indicate that leaky gut and dysbiosis can exacerbate secondary brain injury and negatively impact long-term neurological outcomes (Rice et al., 2019; Hanscom et al., 2021; Krakovski et al., 2022). (Frontiers)

2. Nutrient Absorption and Brain Repair

The gut is where we absorb:

• Protein and amino acids for tissue repair
• Omega-3 fatty acids for brain cell membranes
• B vitamins, magnesium, and other micronutrients are needed for energy and nerve function

If digestion is poor and the gut lining is inflamed, the brain may not receive the necessary building blocks to heal, which can slow down neuroplasticity and recovery (Flint Rehab, 2025). (Flint Rehab)

3. Mood, Sleep, and Neurotransmitters

The majority of the body’s serotonin, an important neurotransmitter for mood, sleep, pain, and gut motility, is produced in the intestines. Following a TBI, serotonin production and signaling in the gut can be altered due to inflammation, dysbiosis, and changes in motility (El Baassiri et al., 2024). (BioMed Central)

Dysbiosis and leaky gut have been linked to:

• Higher rates of anxiety and depression
• Changes in pain sensitivity
• Cognitive changes, such as brain fog and slower processing

These mood and cognitive symptoms stack on top of the direct brain injury, making life even harder.

4. The Gut–Brain–Spine Connection

Newer writing on the “gut–brain–spine” connection suggests that spinal health also affects the brain–gut axis. Misalignment, poor posture, and spinal tension can alter the way signals travel through the spinal cord and affect autonomic control of the organs (Gordon & Liester, 2025). (Psychology Today)

This is one reason why integrative chiropractic care—focused on the spine, nervous system, and whole-body health—may play a useful role in supporting both brain and gut recovery.

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Integrative Chiropractic Care: Supporting the Brain–Gut Axis

Integrative chiropractic care goes beyond quick spinal adjustments. In many clinics, it combines:

• Precise spine and joint adjustments
• Neurological rehabilitation and balance training
• Soft-tissue work and posture care
• Nutrition and gut health support
• Functional medicine lab testing and targeted supplements

This is especially powerful when the chiropractor is also medically trained, as in the case of Dr. Alexander Jimenez, DC, APRN, FNP-BC, a dual-scope chiropractor and nurse practitioner in El Paso, Texas. His clinics focus on trauma, personal injury, and neuro-musculoskeletal care, with a strong emphasis on gut and metabolic health as part of recovery. (Synergy Chiropractic)

1. Restoring Spinal Alignment and Neural Communication

Spinal misalignments, particularly in the upper cervical spine (C1–C2), can disrupt the way the brainstem and autonomic centers send and receive signals. Correcting these issues can:

• Improve blood flow and cerebrospinal fluid dynamics
• Normalize sensory input from the neck and spine
• Reduce dizziness, headaches, and neck pain that feed stress into the system

Clinical chiropractic and neurology–focused centers report that upper cervical adjustments help restore more normal brain–body communication after TBI, which can indirectly support better autonomic control of the gut (Jimenez, n.d.; Synergy Chiropractic, 2025). (Synergy Chiropractic)

2. Improving Vagal Tone and Autonomic Balance

The vagus nerve is a key pathway in the brain–gut axis. It carries calming parasympathetic signals that slow heart rate, improve digestion, and help control inflammation.

TBI often reduces vagal tone and leads to dysautonomia. Spinal adjustments—especially in the upper neck and mid-back—may stimulate vagal pathways and shift the body toward a calmer, “rest-and-digest” state (Northwest Florida Physicians Group, 2024; Eugene Chiropractic, 2023). (Northwest Florida Physicians Group)

Patients sometimes notice:

• Less racing heart or pounding anxiety
• Improved ability to relax
• Better bowel movements and less abdominal tension
• Reduced nausea and feelings of “butterflies” in the stomach

Psychology and neuroscience writers have also begun to highlight how spinal interventions, breathing exercises, and somatic work can influence the gut–brain–spine axis by enhancing vagal function and reducing stress reactivity (Gordon & Liester, 2025). (Psychology Today)

3. Supporting Gut Barrier and Microbiome Through Integrative Care

Because many integrative chiropractic providers also focus on functional medicine and nutrition, care plans may include:

• Anti-inflammatory, Mediterranean-style diets rich in fruits, vegetables, fish, nuts, and olive oil
• Strategic use of prebiotics (fiber) and probiotics to support microbiome balance
• Nutrients like omega-3s, glutamine, zinc, and polyphenols that support gut barrier integrity
• Guidance to reduce ultra-processed foods, excess sugar, and alcohol

Research suggests that diet and microbiome-targeted therapies may help reduce intestinal permeability, improve intestinal motility, and lower systemic inflammation after brain injury (Krakovski et al., 2022; Rice et al., 2019). (PMC)

Dr. Jimenez’s clinics, for example, integrate chiropractic care with gut-focused functional medicine, advanced imaging, and lab testing to address both structural and metabolic drivers of symptoms in TBI and personal injury patients. (El Paso, TX Doctor Of Chiropractic)

4. Addressing Musculoskeletal Pain That Worsens Gut Symptoms

Painful neck, back, and rib restrictions after a concussion or whiplash can make deep breathing and relaxed posture difficult. When breathing is shallow and the diaphragm is tight, abdominal pressure and motility can be affected.

By releasing joint and soft-tissue restrictions, chiropractic and rehab care can:

• Improve breathing patterns and diaphragm movement
• Reduce muscle guarding in the abdomen and torso
• Lower pain-driven stress, which often aggravates IBS-like symptoms

This musculoskeletal relief helps create the physical and nervous-system conditions necessary for the gut to heal.

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Practical Steps: Supporting Gut and Brain Recovery After TBI

If you or someone you care for has experienced a traumatic brain injury and now struggles with digestive problems, here are practical steps to consider. These are general suggestions, not personal medical advice.

1. Get a Thorough Medical and Neurologic Evaluation

Start by ruling out emergencies and serious GI diseases. Work with:

• A neurologist or brain-injury specialist
• A primary care provider or nurse practitioner
• A gastroenterologist if symptoms are severe, bloody, or long-lasting

Ask specifically about the brain–gut connection and whether your gut issues might be related to TBI rather than being dismissed as “just stress.”

2. Track Symptoms in a Simple Log

Write down:

• What and when you eat
• Bowel habits (constipation, diarrhea, pain)
• Nausea, bloating, and reflux
• Brain symptoms (headache, dizziness, fatigue, mood)

Patterns can help your care team connect brain, gut, and lifestyle triggers.

3. Focus on a Gentle, Anti-Inflammatory Eating Pattern

In many TBI patients, a Mediterranean-style pattern is a good starting point:

• Plenty of vegetables and fruits
• Whole grains, beans, and lentils, if tolerated
• Healthy fats (olive oil, avocado, nuts, seeds)
• Fish and lean proteins
• Limited processed foods, sugary drinks, and fried foods

If you suspect food sensitivities, work with a clinician experienced in TBI and gut health. Avoid extreme diets unless supervised.

4. Support the Microbiome Carefully

With guidance from your provider, consider:

• Gradually increasing fiber from vegetables, fruits, oats, and legumes
• Adding fermented foods like yogurt with live cultures, kefir, sauerkraut, or kimchi
• Considering probiotics if appropriate

Research suggests that microbiome-targeted therapies can improve motility, intestinal permeability, and inflammatory markers in TBI models (Rice et al., 2019). (Frontiers)

5. Move Gently and Regularly

Even light movement can:

• Stimulate gut motility
• Improve mood and sleep
• Reduce stress and muscle tightness

Walking, gentle stretching, and balance exercises from rehab programs can be adjusted to your tolerance.

6. Work With an Integrative Chiropractic Provider

Look for a chiropractor who:

• Understands concussion and TBI
• Evaluates posture, spinal alignment, and nervous-system function
• Coordinates with neurologists and other medical providers
• Can address gut and metabolic factors through integrative or functional medicine

Clinics like those led by Dr. Alexander Jimenez in El Paso blend chiropractic adjustments, neurologic rehab, and gut-focused functional medicine to address the whole brain–gut–spine system—not just one symptom at a time. (Synergy Chiropractic)

7. Manage Stress and Sleep

Stress and poor sleep have a significant impact on both the gut and the brain. Helpful tools include:

• Breath-work and vagus-nerve–focused exercises
• Mindfulness, meditation, or prayer
• Gentle yoga or tai chi
• A consistent sleep schedule and a dark, quiet bedroom

These practices can improve autonomic balance and support both digestive and neurological healing (Gordon & Liester, 2025). (Psychology Today)

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When to Seek Immediate Help

Call your doctor or seek urgent care if you have:

• Severe or sudden abdominal pain
• Vomiting that won’t stop
• Blood in stool or black, tarry stools
• Unexplained high fever, chills, or signs of infection
• Rapid weight loss, severe dehydration, or fainting

These may be signs of a serious GI issue that needs immediate attention, even if you have a history of TBI.

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Putting It All Together

After a traumatic brain injury, the gut often becomes an overlooked victim. TBI can:

• Increase intestinal permeability (“leaky gut”)
• Disturb the microbiome and immune system
• Disrupt the autonomic and enteric nervous system control of digestion
• Trigger nausea, constipation, diarrhea, and other stomach problems

These gut changes can, in turn, worsen brain inflammation, mood, and cognition—creating a frustrating loop of symptoms.

The good news is that the brain–gut axis is changeable. Integrative chiropractic care that supports spinal alignment, vagal tone, and overall nervous-system balance—combined with targeted diet, microbiome support, and stress reduction—offers a promising path to support both brain and gut recovery.

Working with experienced clinicians, such as integrative chiropractors and nurse practitioners who understand TBI (like Dr. Alexander Jimenez and his team in El Paso), can help you develop a personalized plan that addresses the root causes of your symptoms and supports the long-term healing of both the brain and the gut.

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References

Albert, V. (2025). Role of the gut–brain axis in severe traumatic brain injury. Current Neurology and Neuroscience Reports, 25(1), 1–15. (Thieme)

Davis, B. T., IV, et al. (2021). Differential fecal microbiome dysbiosis after equivalent traumatic brain injury in aged versus young adult mice. Journal of Neurotrauma, 38(17), 2390–2403. (Scientific Archives)

El Baassiri, M. G., et al. (2024). Dysregulated brain–gut axis in the setting of traumatic brain injury: Review of mechanisms and anti-inflammatory pharmacotherapies. Journal of Neuroinflammation, 21, 1–28. (BioMed Central)

Fong, A. (2024). Post-concussion stomach problems: Loss of appetite, food sensitivity, acid reflux, and more. Cognitive FX Blog. (cognitivefxusa.com)

Flint Rehab. (2025). Brain injury and gut health: Looking at the gut-brain axis and how the connection can impact TBI recovery. Flint Rehab Neurological Recovery Blog. (Flint Rehab)

Ghaemi, M. (2025). The gut-brain axis in traumatic brain injury: Literature review. Neuroscience & Biobehavioral Reviews, 159, 105567. (ScienceDirect)

Gordon, D., & Liester, J. (2025). The gut–brain–spine connection. Psychology Today. (Psychology Today)

Hanscom, M., Loane, D. J., & Shea-Donohue, T. (2021). Brain–gut axis dysfunction in the pathogenesis of traumatic brain injury. Journal of Clinical Investigation, 131(12), e143777. (PubMed)

Jimenez, A. I. (2025). Chiropractic for traumatic brain injury recovery in El Paso. Synergy Chiropractic. (Synergy Chiropractic)

Krakovski, M. A., et al. (2022). Diet–microbiome–gut–brain nexus in acute and chronic brain injury. Frontiers in Neuroscience, 16, 1002266. (PMC)

Northwest Florida Physicians Group. (2024). Using chiropractic care to treat traumatic brain injuries. (Northwest Florida Physicians Group)

Rice, M. W., et al. (2019). Gut microbiota as a therapeutic target to ameliorate the biochemical, neuroanatomical, and behavioral effects of traumatic brain injuries. Frontiers in Neurology, 10, 875. (Frontiers)

Synergy Chiropractic / Dr. Alexander Jimenez. (n.d.). El Paso’s premier chiropractic clinic – Injury Medical Pain Treatment Clinic. dralexjimenez.com. (El Paso, TX Doctor Of Chiropractic)

Zhu, C. S., et al. (2018). A review of traumatic brain injury and the gut microbiome. Journal of Neurotrauma, 35(3), 573–584. (PMC)

Eugene Chiropractic. (2023). Can chiropractic care improve your gut health?. (eugenechiropractor.com)

(Additional articles from the user’s source list—such as Psychology Today’s Fixing the gut-brain chaos after head injury and related TBI–gut axis reviews—also support the concepts discussed here.) (Psychology Today)