The Science Behind Brain Fog

Have you ever walked into a room and then forgotten why you walked in there? Are you struggling to focus or losing your train of thought in the middle of a sentence? This could be brain fog, and the cause of this might be on your plate.

Brain fog is a common yet often misunderstood health complaint. Frequently dismissed as “normal,” it affects an estimated 20–30% of the Australian population. Having personally experienced this, I know firsthand how frustrating it can be. Think of brain fog as your body’s feedback system, an internal signal asking you to pay attention. It is not a diagnosis, it is information. When you start listening to it, you can uncover what is really happening beneath the surface.

There is rarely one single cause. Brain fog often reflects a network of interconnected imbalances:

1. Sleep: Without deep, restorative sleep, your brain struggles to recharge and process information effectively.

   
   

2. Stress: Chronic stress elevates cortisol, which can impair focus, mood, and memory.

   
   

3. Gut Health: The gut and brain communicate constantly. When the gut microbiome is out of balance, fermentation of foods by yeast and bacteria can produce alcohol and toxins, and proteins in gluten and dairy can produce morphine-like compounds. These factors can affect mental clarity, energy, and cravings.

   
   

4. Inflammation: Low-grade inflammation interferes with how brain cells communicate and can leave you feeling mentally drained.

   
   

5. Blood Sugar Swings: When blood glucose levels rise and fall rapidly, energy and concentration often follow the same pattern.

   
   

6. Nutrient Deficiencies: Inadequate intake of key nutrients such as B vitamins, omega-3 fatty acids, magnesium, vitamin D, and iron can disrupt energy production and brain function.

The encouraging part is that brain fog is reversible. You do not have to live with it or push through it. When you begin to see it as the body’s call for balance, you can start addressing the underlying causes. Supporting sleep, managing stress, nourishing the gut, and stabilising blood sugar can all help restore clarity and energy. Your body is always communicating with you. 

When you slow down, listen, and respond with care, the fog begins to lift. You start to think clearly again, feel more focused, and reconnect with your natural energy and vitality.

The Gut–Brain Connection

Your gut and brain are in constant communication. This connection, often called the gut–brain axis, means that the health of your digestive system directly affects how clearly you think, how well you focus, and how you feel emotionally.

The lining of the gut acts as a barrier, controlling what gets absorbed into the bloodstream. When this lining is irritated or inflamed, it can trigger signals that affect brain function. At the same time, trillions of bacteria in the gut microbiome produce chemicals and neurotransmitters that influence mood, energy, and cognitive clarity. When the microbiome is out of balance, inflammation and chemical changes can cloud thinking and contribute to brain fog.

Symptoms that may indicate a gut imbalance include bloating, irregular bowel movements, food sensitivities, fatigue, and low mood. Even subtle digestive issues can reduce mental clarity and slow cognitive performance.

A simple way to think about this is to imagine your gut as a control centre for your energy and focus. When it is functioning well, messages to the brain are clear and efficient, and your mind feels sharp. When the gut is stressed or inflamed, messages become distorted, leaving your thoughts cloudy and your energy low. Emerging research shows that gut inflammation, whether from stress, infections, yeast overgrowth, or dysbiosis, can affect brain function in both the short and long term.

The good news is that supporting your gut can have a profound effect on mental clarity and energy. Improving the gut lining, nurturing a balanced microbiome, and reducing inflammation can sharpen your focus, boost your energy, and help you feel like yourself again.

The Worst Foods for Brain Fog

Gluten

For some people, gluten can irritate the gut lining, promote low-grade inflammation, and produce morphine-like peptides that affect the brain. This can lead to brain fog, fatigue, or difficulty concentrating. Gluten is not harmful for everyone, but reducing or avoiding it temporarily can help identify if it contributes to your symptoms.

Dairy

Dairy can be a double-edged sword. Some individuals react to A1 casein in cow’s milk, which can trigger gut inflammation and worsen brain fog, while A2 dairy or fermented products like yogurt may be better tolerated. High-quality, moderate dairy can be fine for many, but sensitivity can reduce mental clarity.

Artificial Sweeteners

Artificial sweeteners can alter the gut microbiome and disrupt neurotransmitter production. This can leave you feeling foggy or low in energy. Occasional use may not be an issue, but frequent consumption can make it harder for the gut and brain to function optimally.

Alcohol

Alcohol irritates the gut lining, disrupts the microbiome, and promotes inflammation. Even moderate intake can affect sleep, nutrient absorption, and cognitive performance, contributing to mental sluggishness and fatigue. Reducing or spacing alcohol intake supports both gut health and mental clarity.

Ultra-Processed Foods

Highly processed foods are designed to be hyper-palatable. They are often high in refined sugars, refined grains, and additives. These foods inflame the gut, disrupt the microbiome, and spike blood sugar. This can create peaks and crashes in energy, poor focus, and brain fog. Prioritising whole, minimally processed foods protects both gut and mind.

Not everyone reacts the same way, but if you experience frequent brain fog, experimenting with reducing these foods can be a powerful first step.

When the right foods support the gut and problematic foods are reduced, mental clarity returns, energy stabilises, and fatigue diminishes. Even small, consistent adjustments make a meaningful difference.

Persistent brain fog can feel discouraging, but it is not permanent. Your body is communicating with you. Every positive step, whether supporting sleep, nourishing your gut, or reducing a trigger food, brings you closer to clarity and vitality.

TIP: A simple step you can take today is to start a food and symptom journal. Note what you eat and how you feel over the next few days. This habit can reveal patterns and give you a clear starting point for improving your gut and your brain.

You do not have to live in a mental haze. By supporting your gut and discovering your food triggers, you can bring back clarity, energy, and focus one meal at a time. Brain fog is not just in your head. It is often in your gut. The good news is that this means you have more power to change it than you might think.

If you are ready to regain mental clarity and energy, take the next step! Book a personalised nutrition consultation to identify your food triggers and support your gut health.

BOOK NOW

References:

1. Faraz Bishehsari, Magno, E., Swanson, G., Desai, V., Voigt, R.M., Forsyth, C.B. and Keshavarzian, A. (2017). Alcohol and Gut-Derived Inflammation. Alcohol Research : Current Reviews, [online] 38(2), p.163. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC5513683

2. Gomes Gonçalves, N., Vidal Ferreira, N., Khandpur, N., Martinez Steele, E., Bertazzi Levy, R., Andrade Lotufo, P., Bensenor, I.M., Caramelli, P., Alvim de Matos, S.M., Marchioni, D.M. and Suemoto, C.K. (2022). Association Between Consumption of Ultraprocessed Foods and Cognitive Decline. JAMA Neurology, [online] 80(2). doi:https://doi.org/10.1001/jamaneurol.2022.4397

3. Jianqin, S., Leiming, X., Lu, X., Yelland, G.W., Ni, J. and Clarke, A.J. (2016). Effects of milk containing only A2 beta casein versus milk containing both A1 and A2 beta casein proteins on gastrointestinal physiology, symptoms of discomfort, and cognitive behavior of people with self-reported intolerance to traditional cows’ milk. Nutrition Journal, 15(1). doi:https://doi.org/10.1186/s12937-016-0147-z

4. Premraj, L., Kannapadi, N.V., Briggs, J., Seal, S.M., Battaglini, D., Fanning, J., Suen, J., Robba, C., Fraser, J. and Cho, S.-M. (2022). Mid and long-term neurological and neuropsychiatric manifestations of post-COVID-19 syndrome: A meta-analysis. Journal of the Neurological Sciences, 434, p.120162. doi:https://doi.org/10.1016/j.jns.2022.120162

5. Topiwala, A., Allan, C.L., Valkanova, V., Zsoldos, E., Filippini, N., Sexton, C., Mahmood, A., Fooks, P., Singh-Manoux, A., Mackay, C.E., Kivimäki, M. and Ebmeier, K.P. (2017). Moderate alcohol consumption as risk factor for adverse brain outcomes and cognitive decline: longitudinal cohort study. BMJ, [online] 357(8109), p.j2353. doi:https://doi.org/10.1136/bmj.j2353