Brain fog… it comes down to biology.
The brain is the most energy-demanding organ in the body. Despite making up only a small percentage of our body weight, it requires a constant and reliable supply of fuel to support memory, focus, mood, motivation, emotional regulation and temperature control. When this energy system is under strain, or demand outweighs production, symptoms often appear as brain-fog, fatigue, low mood, anxiety, irritability and poor concentration… sound familiar?!
At the heart of this story sit three tightly connected systems: metabolic health, hormones, and the mitochondria, the tiny powerhouses inside every brain cell.
The Brain: An Energy-Hungry Organ
For the brain to function optimally, it relies on several key factors working together:
-
Stable blood sugar levels
-
Adequate nutrients: glucose or ketones (from fat), protein (amino acids), B-vitamins, magnesium, omega-3 fatty acids, iron, CoQ10, creatine and anti-oxidant protection
-
Healthy mitochondria to produce ATP (cellular energy)
-
Hormonal signals that regulate fuel availability
When any one of these systems is compromised, cognitive performance is often the first thing to suffer… Brain-fog ensues!
Blood Sugar, Metabolic Health & Brain Energy
Fluctuating blood sugar levels are one of the biggest drivers of inconsistent energy and brain fog. What we eat determines how high blood sugar rises and how efficiently glucose is delivered into cells for energy.
Our ability to manage blood sugar effectively declines with physical inactivity, loss of muscle mass, ageing, low magnesium levels and, critically for women, hormonal changes during perimenopause and menopause.
Insulin sensitivity, the ability of insulin to move glucose into cells, is positively influenced by magnesium, omega-3 fatty acids, muscle mass, regular movement and sex hormones, particularly oestrogen. When insulin sensitivity drops, brain cells experience an energy shortfall, even when there is plenty of glucose circulating in the bloodstream.
Daily Eating Habits That Support Brain Energy
Simple, consistent habits can dramatically improve mental clarity:
Prioritising protein and fibre at every meal helps slow blood sugar spikes and provides the brain with steady fuel. B-vitamins are essential here, as they are required for energy production at the cellular level. Liposomal B-Complex can be a simple way of supporting your B-Vitamin levels.
Minimising ultra-processed and highly sweetened foods reduces blood sugar volatility, while whole foods support metabolic flexibility.
Focusing on magnesium rich foods such as cacao, seeds and nuts and leafy greens, omega-3 fatty acids and fibre further improves insulin sensitivity and mitochondrial efficiency.
Creatine & the Hungry Brain
Creatine is often associated with muscle, but it also plays a vital role in brain energy metabolism. Found naturally in meat and fish, creatine supports mitochondrial integrity and improves fuel availability in high-demand tissues like the brain.
Women store and produce less creatine than men, making adequate intake especially relevant. During periods of hormonal fluctuation, 5g of supplemental creatine monohydrate may help buffer against the energy shortfalls that show up as mental fatigue and brain fog.
The Sex Hormone–Brain Connection
Different regions of the brain are densely packed with oestrogen receptors located directly on mitochondria. These include the hippocampus (memory and learning), hypothalamus (energy balance and temperature regulation), prefrontal cortex (focus and cognition) and amygdala (mood and emotional regulation).
This reveals something crucial: oestrogen helps regulate brain function through its effects on energy production.
Mitochondria, Oestrogen & Brain Fog
Healthy mitochondria efficiently produce ATP. When they become dysfunctional, they produce less energy, generate more inflammation and increase oxidative stress. This energy-system failure contributes to fatigue, cognitive decline and tissue degeneration.
Before menopause, higher oestrogen levels support efficient mitochondrial function, consistent brain energy supply and antioxidant protection. During perimenopause, fluctuating and declining oestrogen leads to reduced ATP production, increased oxidative stress and poor fuel availability in key brain regions.
This underpins many common symptoms, including brain fog, low mood, anxiety, irritability, hot flushes and changes in metabolic health. Oestrogen also boosts antioxidant systems such as glutathione and protective enzymes like SOD. As levels decline, the brain becomes more vulnerable to oxidative damage.
Why Supporting Mitochondria Matters in Midlife
Mitochondrial dysfunction is a key feature of ageing and is associated with neurodegenerative disease, metabolic syndrome, cardiovascular disease and cognitive decline. Improving mitochondrial efficiency can support memory, attention, mood, emotional resilience, temperature regulation and overall cognitive performance, particularly during hormonal transitions.
Omega-3s & Key Nutrients for Mitochondrial Health
Omega-3 fatty acids are critical for brain mitochondrial health. They enhance ATP production, support neuronal membrane fluidity, reduce oxidative stress, promote neuroprotection and are associated with reduced risk of age-related cognitive decline.
Mitochondria also depend on a wide range of micronutrients, including B-vitamins, iron, magnesium, CoQ10 and antioxidants such as vitamins C and E, selenium and zinc. Together, these nutrients enable efficient energy production and protect mitochondria from oxidative damage.
The Take-Home Message
Brain fog is not “all in your head”. It is a signal from an energy system under strain.
Your metabolic health is central to brain health, and mitochondria are the cellular batteries that power nearly all energy production. Hormonal changes directly influence mitochondrial function in the brain, making midlife a critical window for support.
Protecting and fuelling your mitochondria through whole-food nutrition, key nutrients, movement, muscle mass and time outdoors can strengthen brain energy, clarity and resilience at every stage of life.
For the Full Instagram Live on Brain-Fog and Hormone Health watch here