What Causes Brain Fog? A Systems-Based Look at the Root Causes
If you’ve ever found yourself walking into a room and forgetting why, struggling to find the right words during a conversation, or feeling like your brain is stuck in a haze—you’re not alone.
You are likely dealing with brain fog and have probably thought what causes brain fog?
“Brain fog” is one of the most common complaints we hear in our clinic, Peak Brain and Body a functional medicine and functional neurology clinic in Wesley Chapel. Some know it’s an issue they want addressed, but others aren’t sure if it’s just a normal part of aging. Yet despite how widespread it is, it’s often dismissed, misunderstood, or chalked up to aging, stress, or hormones. But here’s the truth:
Brain fog is not “just in your head.” It’s your body’s way of telling you that something deeper is off, but it’s non-specific.
In this article, we’re going to explore six major systems in the body that can cause or contribute to brain fog—many of which are often overlooked by conventional healthcare. If you’re someone who’s tried supplements, changed your diet, and still feels “off,” this deep dive is for you.
You may also watch it here: https://www.youtube.com/live/YDeuV-rS8I0
What Is Brain Fog?
First things first: brain fog isn’t a diagnosis. It’s a symptom – a signal that something in your body is out of balance. It might show up as:
- Difficulty focusing or concentrating
- Forgetting common words or losing your train of thought mid-sentence
- Feeling mentally fatigued even after sleeping well
- Zoning out or spacing out during the day
- A sense that your brain is “in a cloud”
And while it’s common, it’s not always normal – especially when it starts affecting your daily life, your relationships, and your ability to work and connect with others.
Now let’s look at why brain fog happens and what your body may be trying to tell you. Remember brain fog is always a neurological symptom, but it may not always be due to poor brain health and may be the result of problems in other parts of the body.
So, what causes brain fog?
The Six Body Systems That Can Cause Brain Fog
1. Gastrointestinal (Gut) Health and Brain Fog
Your gut and your brain are intimately connected through what scientists call the gut-brain axis. The bacteria in your gut produce neurotransmitters, influence inflammation levels through metabolites known as short chain fatty acids, and communicate directly with your nervous system.
When something is off in the gut, your brain may be impacted.
Common gut-related contributors to brain fog:
- Dysbiosis: An imbalance in gut bacteria. You may have too many harmful bacteria or too few of the beneficial ones. This disrupts digestion, nutrient absorption, and produces inflammatory byproducts that can affect brain function.
- Leaky Gut (Intestinal Permeability): When the gut lining becomes too porous, it allows toxins, food particles, and bacteria to enter the bloodstream and trigger systemic inflammation, including in the brain.
- Processed Foods & Inflammatory Diets: Diets high in sugar, refined carbs, and additives fuel inflammation in both the gut and brain. For some over time, this leads to decreased mental clarity. For others, they may notice changes in brain function minutes or hours after eating foods or drinking certain things.
How to address it:
- Track your food intake for 7 days. Cut out ultra-processed foods and added sugars as a good starting point.
- Consider an elimination diet or Paleo-style eating plan (vegetables, high-quality proteins, healthy fats). Track how you feel with the dietary changes. If you try to reintroduce foods see if you have a negative change in any symptoms; if you do then it’s best to avoid those foods.
- If you’ve cleaned up your nutrition and symptoms persist, stool testing can evaluate your microbiome and identify dysbiosis, pathogens, or leaky gut markers. This allows you to receive a specific treatment tailored for you.
2. Neurological Function and Brain Fog
Brain fog is a neurological symptom, meaning something is disrupting the way your brain functions. It could be:
- Old concussions (even ones from years ago). In our experience 90% of individuals who are still struggling with concussion issues have no clue it’s what is keeping them stuck.
- Neurological inefficiency (your brain is working too hard to complete simple tasks)
- Visual processing- the brain has to take in an enormous amount of information. This information is taxing on the brain. Problems with eye movement function such as gaze fixation, pursuits, saccades, and vergence can lead to brain fog.
Your brain uses more energy than any other organ. When it becomes inefficient – whether due to an old injury, eye strain, or abnormal sensory input – it starts to feel foggy.
Brain Testing & evaluation:
- Computerized eye movement testing (video oculography) evaluates gaze fixation, saccades, and pursuits. Nearly 99% of our patients have never had this test performed. It’s off in upwards of 75% of the individuals we see and is a big part of their inability to get the results they want until it gets addressed.
- Balance testing and qEEG (quantitative EEG) identify areas of neurological inefficiency.
- A thorough history can reveal concussions that may have been overlooked or dismissed.
Addressing neurological function isn’t just for athletes – it’s often the missing piece for those who have tried everything else such as hormones, b-vitamins, thyroid, and other things.
3. Cardiovascular Health and Brain Fog
Your brain relies on constant, efficient blood flow to function. If your cardiovascular system isn’t working well, your brain may be under-supplied with oxygen and nutrients.
Subtle cardiovascular contributors to brain fog include:
- High blood pressure or undiagnosed hypertension
- Hypotension such as seen in dysautonomia
- Elevated triglycerides or cholesterol
- Inflammatory markers like homocysteine
- Lipoprotein(a) and ApoB (which increase your risk of plaque buildup)
- Low omega-3 fatty acid intake
How to evaluate it:
- Full lipid panel including ApoB and Lipoprotein(a)
- Homocysteine levels
- Omega-3 to omega-6 ratio
- Coronary artery calcium (CAC) scan to assess plaque buildup
Even if you feel “fine,” silent cardiovascular issues could be stealing your brain’s clarity. It takes years for cardiovascular issues to manifest as something bad, prevention is key.
4. Immune System & Chronic Inflammation Contributing to Brain Fog
Chronic inflammation is one of the most common underlying causes of brain fog. When your immune system is out of balance, your brain function can suffer. The key is to identify what impacts the immune system. It should be noted that many of the things that have already been talked about also drive changes in the immune system.
Major immune contributors to brain fog:
- Chronic infections: Epstein-Barr virus, herpes virus, Candida, and gut infections that usually don’t cause fevers can cause chronic inflammation and drive brain fog.
- Mold exposure: Can cause inflammatory reactions in sensitive individuals who have an immune response. This is more than exposure as not everyone who is exposed will develop symptoms.
- Autoimmunity: Your immune system attacking your own tissues (including the brain). Common autoimmune conditions include: lupus, multiple sclerosis, hashimoto’s, rheumatoid arthritis, crohn’s, and ulcerative colitis usually all come with symptoms of brain fog.
How to evaluate it:
- Immune testing for mold (IgG, IgE antibodies to mycotoxins) is preferred over urinary screenings.
- ANA panel (anti-nuclear antibodies) and tissue specific autoimmune markers based on symptoms and history.
- Lab specific testing for chronic infections that is best performed via blood or stool testing depending on the pathogen.
- Autoimmunity is a spectrum. Many individuals will go years before they are diagnosed. Most get diagnosed at the point of tissue destruction versus the early stage of the disease process where autoimmune markers are present.
The earlier you detect immune dysfunction, the more you can do to prevent full-blown autoimmune conditions.
5. Musculoskeletal System and Brain Fog
Tension, misalignment, or dysfunction in the muscles and joints of your upper spine, neck, or jaw can contribute to pain and brain fog.
Key physical contributors:
- TMJ dysfunction (tenderness or tightness in the jaw)
- Neck misalignment or tension
- Poor posture from screen use
While chiropractic care can help in some cases, musculoskeletal issues are rarely the only cause of brain fog. But if you also have neck pain or headaches, it should be evaluated. If you see great results then fantastic, but if not remember there is more to the picture.
Self-check: Press gently where your jaw hinges, just below your temples. If it’s tender, you may benefit from TMJ therapy or manual work on those muscles.
6. Endocrine System (Hormones & Blood Sugar) and Brain Fog
Hormonal imbalances and blood sugar instability are major drivers of brain fog.
Top endocrine contributors:
- Thyroid dysfunction impacts the rate at which the cells in the brain function. When the rate is slow, then brain fog is common. The most common cause of low thyroid is autoimmune and is known as Hashimoto’s.
- Sex hormone imbalance (estrogen, progesterone, testosterone). These hormones are for more than sexual development and having babies. They play a critical role in immune and neurological health. When these are low or out of balance the brain is routinely impacted.
- Insulin resistance or blood sugar imbalance. Blood sugar that is too high or low impacts brain health. You do not need to be diabetic in order for blood sugar issues to be causing brain fog.
Lab work to ask for:
- Full thyroid panel: TSH, Free T3, Free T4, Total T3, Total T4, Thyroid antibodies
- Sex hormones: Free and total testosterone, estradiol, progesterone, total estrogen. These have less value for females who have regular cycles.
- Blood sugar: Fasting glucose, insulin, C-peptide, triglycerides, oral glucose tolerance test (OGTT). Blood sugar and insulin levels should be back to fasting levels 3 hours after eating.
If you feel tired or foggy after eating, your blood sugar may be on a roller coaster. Start by tracking how food affects your energy.
Peak Brain and Body Treatment For Brain Fog
If you’ve seen multiple providers and still feel foggy, it’s not your fault. Most primary care visits are rushed. Most specialists only focus on one system.
The reality is: brain fog is usually not caused by just one thing. It’s a sign that your body is out of balance in multiple areas.
That’s why at Peak Brain and Body in Wesley Chapel, we use an integrated, systems-based approach to uncover the unique combination of factors affecting each patient. By looking at your body as a whole, we can build a targeted plan to help you regain your clarity, energy, and focus.
We look at both brain and body health, not one or the other. This allows us to identify the pieces of your puzzle that are contributing to brain fog.
You Deserve to Feel Sharp Again
If brain fog is interfering with your work, your relationships, or your sense of self, don’t ignore it.
The earlier you uncover the root causes, the sooner you can start reversing the damage. And yes—for most people, brain fog is reversible. You won’t have to wonder any longer what causes brain fog.
Individuals routinely turn to Peak Brain and Body in Wesley Chapel as a trusted center for Functional Medicine and Functional Neurology to find answers to chronic and complex symptoms and conditions.
If you’re ready to stop guessing and start healing, we’re here to help.
Request a Discovery Consult with our team today.
About Dr. Spencer Zimmerman
Dr. Z is a dual-licensed Nurse Practitioner and Chiropractor—and is the only dual-licensed provider in Florida with advanced training in Functional Neurology, Functional Medicine, and Peptide Therapy. He is the best-selling author of Brain Reset: 7 Steps to a Healthier Brain and the founder of Peak Brain and Body in Wesley Chapel, FL.
