Most of us know the irritation of entering a room and immediately forgetting why we went there.
Brain fog, however, is far more than a fleeting lapse of memory. That persistent, frustrating sense of mental cloudiness is a different kettle of fish and should not be dismissed.
The condition is thought to affect about one in three Britons, including roughly two-thirds of menopausal women. Those experiencing it may struggle to concentrate on straightforward tasks, lose track of words, names and places, and contend with overwhelming tiredness.
There is, though, some reassuring news. New research indicates that experiencing brain fog does not necessarily mean the brain itself is failing.
Researchers at King’s College London found little variation in cognitive-test results between menopausal women who reported brain fog and those who did not.
According to experts, the sensation is more likely to be linked to factors such as lifestyle and stress. In many cases, small but meaningful changes could help ease the problem.
Leading neuroscientists explain what may be driving the troubling symptom and outline surprisingly straightforward steps that could help clear the haze.
Experts told Our News Outlet that low levels of vitamin B12 and iron may cause fatigue, brain fog and shortness of breath
What exactly is brain fog?
Neuroscientist Sabina Brennan, author of Beating Brain Fog, says the experience is not the same as feeling mentally sluggish after a long flight or several nights of poor sleep.
‘It is persistent, occurs regularly and can interfere with the quality of your life, your relationships, and your work,’ she says.
Although researchers have not yet found evidence of physical changes in the brain, specialists say brain fog can sometimes point to an underlying health problem.
‘I see brain fog as a sign that something is amiss; a signal to take action,’ explains Dr Brennan.
‘A doctor should take a medical history, examine you and possibly order blood and other tests.’
Potential causes include illnesses that reduce the amount of oxygen reaching the bloodstream, including asthma, bronchiectasis and chronic bronchitis.
Sleep-disrupting conditions such as gastro-eosophageal reflux disease and sleep apnoea may also contribute, Dr Brennan says. Inflammatory diseases, including lupus and coeliac disease, are possible culprits too.
The immune system releases inflammatory compounds during these conditions, and they can disrupt neurotransmitters involved in memory and learning.
‘It may also be the side effect of a medication taken for high blood pressure or cardiovascular disease,’ says Dr Brennan.
The 1p pill that could ease a foggy mind
Nutritional deficiencies are another frequently overlooked explanation for brain fog, experts say.
Nutritionist Cara Shaw believes insufficient iron may be responsible in some cases, particularly because iron deficiency affects around one-third of women.
Research suggests that about two-thirds of people with low iron levels may not realise they have a deficiency. The mineral is found in foods including leafy green vegetables and red meat.
In a 2007 trial conducted by researchers at Pennsylvania State University, 149 women between 18 and 35 were either given iron supplements or a placebo over a sixteen week period.
Those who boosted their iron stores saw improvement in brain fog, and researchers concluded iron status is a significant factor in cognitive performance, especially in women of reproductive age.
The nutrient is crucial as it helps red blood cells and proteins deliver ample oxygen to several areas of the brain. It also contributes towards the production of chemicals involved in mood like dopamine, serotonin, and noradrenaline.
Women who menstruate are particularly vulnerable to iron deficiency due to the loss of the nutrient during monthly bleeds.
Supplements for B12 can be taken as tablets or injections, and can be prescribed by a doctor
Low levels of vitamin B12 are also worth considering, according to Shaw.
Studies show at least 2 million people of working age are deficient in the nutrient – which is found in meat, fish, poultry and eggs.
Those who eat vegan or vegetarian diets are at particularly high risk, as vegetable sources of the mineral provide very little of it.
B12 is crucial for maintaining myelin – the fatty material surrounding nerve fibres that allows electrical signals to travel between the brain and body.
A lack of it can result in problems with memory and concentration as well as physical issues like pins and needles and unsteadiness.
A major review published last year, involving data from 10 studies, concluded that B12 supplements significantly improve memory, thinking and other cognitive functions in those with a genuine deficiency.
However data shows that those without deficiency – or those considered borderline – are unlikely to see much benefit.
Beyond taking supplements that correct deficiencies, there’s also evidence to suggest that creatine could help with some of the symptoms associated with brain fog.
The popular workout supplement is a substance produced naturally by the body that acts as a rapid back-up energy supply for cells.
While most is stored in muscle, the brain uses creatine too, prompting scientists to investigate whether supplements might improve memory, concentration and mental fatigue.
A 2024 meta-analysis by Chinese researchers reviewed 16 high-quality trials and found creatine supplementation was associated with improved memory, attention time, and processing speeds.
Some studies have seen small cognitive benefits with around 3-5g of the supplement per day, while others have demonstrated the usefulness of creatine in poor sleepers.
A 2024 experiment deliberately sleep-deprived participants for 21 hours, then investigated what happened when they received a single dose of creatine or placebo.
German researchers not only tested cognition but used scans to measure what was happening to energy-related compounds in the brain.
Creatine improved cognitive performance and partially counteracted the negative brain changes and cognitive deterioration produced by sleep deprivation.
The scientists concluded that creatine may be most useful when the brain is under unusually high metabolic demand.
However, the benefit was seen when participants were given a one-off dose of 0.35g per kilogram of body weight. For a 70kg person that’s 24.5g at once, which could result in side effects such as stomach pain.
And while many advocate for the use of hormone replacement therapy to counter menopause-related brain fog, scientific evidence does not prove its direct benefit.
However, studies show the treatment – which consists of oestrogen and progesterone – can improve other symptoms that impact cognition, like hot flushes that interrupt sleep.
Don’t discount ‘obvious’ factors like sleep, caffeine and fitness
If your sleep is disrupted, or lessened, then this alone could be the cause for your brain fog, according to a wealth of data.
Dr Brennan explains there’s a variety of implementable habits you can adopt to help improve your sleep.
Keeping a regular routine, for one, is important – as is opening the curtains when you wake up, dimming lights from 8pm and turning off devices emitting blue light an hour before bed.
Sleeping in a darkened room with blackout blinds, maintaining a cool bedroom, and having a hot bath to lower your core body temperature can all improve quality of sleep.
Then there’s the importance of exercise.
A 2025 Australian review involving more than 250,000 participants found even exercising just once a week was enough to significantly improve general cognition.
‘Movement increases blood flow and can improve alertness, while morning daylight helps to regulate the body clock, which indirectly supports sleep and daytime concentration,’ says Ms Shaw.
Dr Brennan says most people fail to realise the impact of their coffee habit on their ability to focus.
She explains that caffeine can temporarily increase alertness by blocking a hormone called adenosine in the brain.
‘But caffeine doesn’t remove adenosine from your system it just blocks the signal – a bit like pressing mute on a meeting or phone call.
‘When caffeine wears off the accumulated adenosine binds to receptors causing a sudden wave of fatigue – too much caffeine, particularly later in the day, can worsen anxiety and disrupt the following night’s sleep, potentially perpetuating the problem.’
