Why You Can’t Think Straight: The Functional Medicine Guide to Brain Fog
- re:health
- Apr 11
- 4 min read
Why Brain Fog Deserves Serious Attention
If you've ever felt mentally “cloudy,” forgetful, or unable to concentrate, you might be experiencing brain fog. It's a common yet poorly understood symptom that often gets brushed aside or mislabelled as stress, ageing, or even laziness. But brain fog is a real and valid experience — and in functional medicine, we see it as a sign that something deeper is going on.
In this blog, we’ll explore:
What brain fog actually is
The most common causes
How testing can uncover hidden drivers
Natural ways to support clearer thinking, focus, and memory
Whether you're navigating perimenopause, recovering from illness, or managing a chronic condition like ADHD or CIRS, understanding brain fog can be the first step towards lasting relief.
What Is Brain Fog?
“Brain fog” isn’t a medical diagnosis, but rather a cluster of cognitive symptoms that may include:
Poor concentration or focus
Mental fatigue
Forgetfulness or word-finding difficulties
Slow processing speed
Disorientation or confusion
Difficulty making decisions
In short, your brain doesn’t feel like it’s firing on all cylinders.
Brain fog is not just a nuisance; it's often a biochemical signal of inflammation, nutrient imbalance, poor detoxification, hormonal fluctuation, or impaired mitochondrial energy production. It’s especially common in people with neuroinflammatory conditions, hormonal shifts (e.g. perimenopause), gut issues, and chronic environmental exposures like mould.
Common Causes of Brain Fog
There is no one-size-fits-all cause of brain fog. It is typically multifactorial, and in our clinic, we look at root causes across several key areas:
1. Blood Sugar Dysregulation
Skipping meals, high-sugar diets, or reactive hypoglycaemia can cause fluctuations in energy and concentration. The brain is highly sensitive to glucose drops, often resulting in foggy thinking, mood swings, or low energy.
2. Inflammation and Neuroinflammation
Chronic systemic inflammation — whether from infections, mould, autoimmune conditions, or leaky gut — can cross the blood-brain barrier and trigger neuroinflammation. This type of inflammation affects memory, clarity, and focus, and is often missed in conventional assessments.
3. Nutrient Deficiencies
Cognitive function is highly dependent on nutrient status. Low levels of B12, iron, vitamin D, omega-3s, magnesium, or choline can all contribute to brain fog. Inadequate methylation (often seen in people with MTHFR or related gene variants) may further impair detoxification and neurotransmitter balance.
4. Hormonal Imbalances
Hormones such as oestrogen, progesterone, thyroid hormones, and cortisol all affect brain function. Perimenopause, thyroid dysfunction, and adrenal dysregulation are frequently overlooked drivers of brain fog in women — especially in their 40s and 50s.
5. Toxicity and Environmental Exposures
Exposure to mould, heavy metals (like mercury or lead), or everyday chemicals can impair mitochondrial function and cognition. In people with genetic susceptibility (such as HLA-DR variants), biotoxins can trigger Chronic Inflammatory Response Syndrome (CIRS), leading to chronic brain-based symptoms.
6. Gut-Brain Axis Dysregulation
Imbalances in the gut — including dysbiosis, SIBO, or leaky gut — can increase systemic inflammation and impair neurotransmitter production. The gut and brain are intimately connected, and what happens in the gut rarely stays in the gut.
7. Mitochondrial Dysfunction
Mitochondria produce the energy your brain cells rely on. When mitochondrial function is impaired — due to oxidative stress, toxins, infections, or nutrient deficits — the result is often low brain energy, poor memory, and mental fatigue.
Functional Medicine Testing for Brain Fog
One of the core principles of our approach is: test, don’t guess. Brain fog is not something to mask — it’s something to investigate. Here are the tests we most often use to uncover the underlying causes:
Blood Chemistry Panel
Looks at B12, iron, blood glucose, thyroid hormones, inflammatory markers (like CRP), and liver and kidney function.
Organic Acids Test (OAT)
Assesses mitochondrial function, neurotransmitter balance, detoxification pathways, and yeast or bacterial overgrowth.
Comprehensive Stool Analysis
Evaluates microbiome health, digestive function, inflammation, and markers of intestinal permeability (leaky gut).
DUTCH Hormone Test
Measures sex hormones and adrenal function across a 24-hour period, including cortisol rhythms and hormone metabolites.
Mycotoxin / CIRS Panel
Includes genetic markers (e.g. HLA-DR), inflammatory cytokines, visual contrast sensitivity (VCS), and biotoxin indicators for mould-related illness.
Nutrigenomics Testing
Assesses SNPs that may impact detoxification, methylation, inflammation, neurotransmitters, or hormonal pathways.
Natural Support for Brain Fog
Once we’ve identified what’s driving your brain fog, we create a personalised plan that often includes:
Foundational Nutrition
A nutrient-dense, anti-inflammatory diet
Sufficient protein, healthy fats, and omega-3s
A focus on stabilising blood sugar throughout the day
Targeted Supplementation
Key nutrients like B-complex, omega-3 DHA, magnesium, NAC, phosphatidylserine, and acetyl-L-carnitine
Herbal adaptogens (e.g. rhodiola or ashwagandha) to support stress regulation
Detoxification and Mitochondrial Support
Support for liver detox pathways
Gentle binders for environmental toxins if needed
Nutrients such as CoQ10, alpha-lipoic acid, PQQ, and glutathione
Lifestyle and Brain-Supporting Habits
Regular movement and morning light exposure
Good sleep hygiene and stress management practices
Cognitive pacing and brain retraining, if required
Final Thoughts
Brain fog is not “just in your head” — it’s often the brain’s way of signalling that something deeper is out of balance. Whether caused by inflammation, hormonal shifts, gut health issues, or environmental toxins, there is a way forward.
With the right investigations and a personalised approach, it is possible to restore clarity, focus, and mental energy — and start feeling like yourself again.
If you’re struggling with brain fog and want to explore what’s driving it, book a free discovery call to find out how we work. We’re here to help you lift the fog and move forward with confidence.
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