How to nourish your brain

Adequate brain energy is essential for cognitive perfor­mance, especially during ageing, which depends on the brain continuing to successfully meet its energy needs. The brain is very energy intensive, accounting for about 20% of our daily energy expenditure, even though it’s only c. 2% of our total body weight. This energy is usually provided by burning glucose, but the brain has the ability to use ketones (made from fats in the liver) when the supply of glucose is disrupted. This ability to use either glucose or ketones provides the brain with a continuous source of fuel to maintain brain function.

Which diet and foods improve brain function?

There’s no one “brain diet” that’s unanimously agreed upon but the bulk of research has been focused on a Mediterranean style diet and cognition. Whilst there are many variations of the Mediterranean diet, you can think of it as putting the emphasis on unprocessed, fibre-rich plant foods (fresh vegetables, fruits, nuts, seeds and legumes), moderate amounts of fish, white meat, dairy and eggs, generous amounts of extra virgin olive oil with less of a focus on red meat. Eating this way can also support mental health with research showing that those who consume higher amounts of fruit and vegetables more frequently are not only likely to be in better physical shape, but are also likely to have enhanced mental wellbeing.

Two other diets have also been found to be helpful. A 2019 review found that all three of the Mediterranean, Dietary Approaches to Stop Hypertension (DASH) and Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) Diets were associated with less cognitive decline and a lower risk of Alzheimer’s disease (a type of dementia). The researchers found that olive oil consumption seemed to be an important part of all three diets.

Another factor that may have been common to all three diets is improved blood sugar control. A long term study, on over 10,000 people, looked at the association of diabetes in middle age with subsequent cognitive decline. It found “Diabetes in midlife was associated with a 19% greater cognitive decline over 20 years”. Interestingly, those with HbA1c in the prediabetic range (5.7-6.4%) also had larger declines than those with HbA1c <5.7%. How many people know that eating to support their blood sugar is also a powerful way to support their cognitive health?

Is there a particular “dementia diet”?

You may have heard of the ketogenic diet discussed in relation to dementia. Simply put, this is a high fat, very low carb, adequate protein diet that, until recently, was used mainly for the treatment of epilepsy. It’s increasingly being used in dementia research. Results are promising but larger and more long term studies are needed.

In the meantime, a combination of the ketogenic and the Mediterranean Diet (MeDi) may be a useful and practical way forward. The ketogenic MeDi diet still includes high vegetable and fruit consumption but slightly increases fat and protein and restricts carbohydrates. This is particularly beneficial for those with poor blood sugar control. 

Are there specific foods for brain health?

Research is ongoing but there are certain foods that are well supported by research and should be part of everyone’s daily nutrition.

Focus on magnesium-rich foods such as almonds, cashews, black beans, brown rice, chia seeds, green leafy vegetables, pumpkin seeds and wholegrains. Magnesium is an essential mineral and particularly important for mental and cognitive health. Dietary magnesium intake is often suboptimal and levels are further depleted by diets high in alcohol and caffeine. Evolving research suggests that chronic stress can lead to magnesium loss/deficiency. Two recent large studies on magnesium and cognition include:

1. A 2023 study on more than 6000 cognitively healthy UK adults (age 40-73) found that people who consume more than 550mg magnesium daily have a younger brain age at 55 (by approx 1 year), compared to people with a normal magnesium intake (around 350mg daily). The study found that higher dietary magnesium is associated with larger brain volumes and concluded: “Higher dietary magnesium intake is related to better brain health in the general population, and particularly in women.”
   
   
2. A 2022 study on over 2500 US adults aged 60 or over, found that a higher intake of dietary magnesium was associated with better cognition in women but not in men.

Consume extra virgin olive oil as often as you can

Extra virgin olive oil is a major feature of a Mediterranean diet and high in health promoting antioxidants but how much should you be consuming? The PREDIMED-NAVARRA trial showed benefits to cognition from supplementing a Mediterranean diet with one litre of extra virgin olive oil a week. A recent small study found that consuming three tablespoons of olive oil daily for six months improved cognitive function in those experiencing mild cognitive impairment. Interestingly, an improvement was seen in both the extra virgin olive oil group and the refined olive oil group. However, we know that extra virgin olive oil is more heat stable due to the higher antioxidant content, so the focus should be on consuming extra virgin olive oil rather than refined olive oil until research proves otherwise.

Eat a minimum of one serving of dark green leafy vegetables every day

These are one of the best sources of vitamin B9 (folate) and packed with the antioxidant, lutein. Dietary folate is associated with a reduced risk of new dementia diagnoses in non-dementia aged populations. Ophthalmologists have long recognised the importance of lutein for eye health and research is increasingly showing that lutein is also important for brain health in young and old alike. Research shows that eating just 1.3 servings daily of green leafy vegetables may help to slow cognitive decline.

Don’t forget to include fish and seafood in your diet

Oily fish, such as salmon, mackerel, trout, anchovies, herring and sardines, are a good source of omega-3 fatty acids, which are important for the brain. Fresh, frozen or tinned are all beneficial. A 2022 meta-analysis of over 30,000 subjects found that people with a high fish consumption had a significantly lower risk of dementia compared to those with low fish consumption.

Weave in some walnuts

Polyphenols are phytochemicals found largely in plant foods that have a beneficial impact on our health. Walnuts have the highest polyphenol content of all the tree nuts. Research has found a significant positive association between walnut consumption and cognitive function among adults of all ages and genders.

Have a wide range of flavanol-rich foods and drinks every day

Apples, berries, cocoa, grapes, pomegranates, herbs, green tea and black tea are all high in a type of phytochemical called flavanols. Flavanols are beneficial chemicals found in plant foods and you may often hear flavanol-rich foods described as “superfoods”. Evolving research suggests that flavanols may support cognitive health and are particularly important for the ageing brain.

Enjoy 30g of dark chocolate (85%+) every day

A 2022 Korean study found that daily consumption of 30g of 85% dark chocolate (high in flavanols) had a significant improvement in mood in just three weeks. Interestingly, the group consuming 70% dark chocolate didn’t see the same mood improvement. The researchers found that the dark chocolate improved the diversity and composition of the gut microbiome and proposed that this may have led to the improvement in mood via the gut-brain axis. Too much chocolate is likely to raise blood sugar and lead to weight gain, so moderation is key.

What to avoid eating

There’s no current evidence that a poor diet alone can cause dementia. However, there are some aspects of a poor diet, such as ultra-processed foods (UPF), that may increase the risk.  There’s increasing evidence to show that consumption of UPF is associated with a wide range of adverse health outcomes including increasing the risk for dementia. The researchers found that even just “replacing 10% of UPF weight in the diet with an equivalent proportion of unprocessed or minimally processed foods was estimated to be associated with a 19% lower risk of dementia.”

Which supplements can be helpful for your brain health?

Not all supplements are equal. There are many poor-quality ones out there, such as those with artificial sweeteners and bulking agents, often found in tablet form. You may want to keep an eye out for these on the ingredients list of your supplement. Look out for the words “bulking agents” and sweeteners, such as sucralose, fructose and aspartame. If in doubt, you might want to research the ingredient.

Multivitamins. A recent study on over 2,200 older adults found that daily multivitamin supplementation for three years improved many aspects of cognition and slowed cognitive decline by 1.8 years or 60%. Benefit was greatest in those with cardiovascular disease.

B vitamins. There is growing evidence that B vitamins are important for maintaining cognition. A 2021 systematic review and meta-analysis concluded that: “B vitamin supplementation is associated with slowing of cognitive decline, especially in populations who received early intervention and intervention of long duration.” Even more recently, a 2022 systematic review and meta-analysis found that: “providing a combination of Omega 3 PUFA and B vitamins as part of a multi nutrient formula benefits cognition in older adults v. a placebo.” Low levels of certain B vitamins (vitamin B6, B9 (Folate) and B12) are associated with elevated levels of homocysteine. High homocysteine has long been recognised as an independent risk factor for dementia.

Omega-3 fatty acids (EPA, DHA & ALA) are important for many areas of health including brain function. Until recently, research on fish oil supplementation was inconclusive but a 2022 paper on over 200,000 participants (aged 60-73) found: “the intake of fish oil supplements was consistently associated with about 13% lower risk of dementia after adjusting for various confounding factors.”

Vitamin D. A 2023 longitudinal study found: “Vitamin D exposure was associated with significantly longer dementia-free survival and lower dementia incidence rate than no exposure.” The effects were much greater in women than in men and also in APOE4 non-carriers versus carriers. APOE4 is one of the genetic risk factors for Alzheimer’s disease. Low vitamin D levels have also been associated with depression. Some experts believe that maintaining serum vitamin D above 75 nmol/L can help to reduce the risk of Alzheimer’s disease and dementia by >30% compared to vitamin D levels of 30 nmol/L.

Magnesium. A 2022 systematic review and meta-analysis found that Alzheimer’s patients have a significantly lower circulating magnesium level than healthy controls. They concluded that: “Magnesium deficiency may be a risk factor for Alzheimer’s Disease and magnesium supplementation may be a potentially valuable adjunctive treatment for Alzheimer’s Disease.”

Hydration is important – are you drinking enough water? 

The human brain is approximately 75% water and dehydration has been shown to impact cognitive performance and mood. Recommended amounts vary but one litre daily was shown to have a positive impact in a study from China. Not all cognitive domains are affected equally. A 2018 meta-analysis found that tasks requiring attention and/or executive function and motor coordination were significantly more impaired when people were dehydrated. A 2023 Spanish study found that dehydration was associated with a greater reduction in cognitive function over a two year period in older adults with metabolic syndrome.

Herbal teas can be a good way of boosting your liquid intake. Lavender and chamomile tea have been used for years for their calming effects before bedtime. A 2022 RCT study on post-menopausal women showed that drinking lavender or chamomile tea helped to alleviate symptoms of depression or anxiety.

Lifestyle habits to support cognitive health

• Keep active. Physical activity can help your brain. A large population study on UK adults found that a higher daily step count was associated with a lower risk of all-cause dementia. They found that just under 10,000 daily steps is optimal. Exercising or walking outside is likely to be even better for your health, with research suggesting that exposure to nature has a positive impact on both mental health and cognitive function. A 2021 meta-analysis found that resistance training was likely to be the best type of exercise for slowing cognitive decline in patients with cognitive dysfunction, especially dementia. Logically, seated resistance exercise would have the same benefits.
  
  
• Prioritise sleep. Our brains are restored by the different phases of sleep. Disrupted sleep is associated with an increased rate of cognitive decline, so we should prioritise good quality sleep. Sleep scientist, Mathew Walker recommends supporting your sleep by getting outside for thirty minutes a day and sleeping in a dark, cool bedroom without gadgets. Other tips that can help improve sleep include getting sufficient morning light, balancing your blood sugar levels and much more.
  
  
• Spend time with other people. An Australian study on >11,000 relatively healthy 70-94-year-olds found that social isolation is associated with worse cognitive function in women but not in men. A more recent examination of 12 longitudinal studies revealed that both social isolation and loneliness were associated with poor cognition in ageing among both genders, and both are risk factors for Alzheimer’s disease-related dementia. Therefore, there’s strong evidence for the need for all genders to spend time with others.
  
  
• Consider including breathing exercises in your daily routine. Emerging research shows promise for stress reduction and improving mood. Just 5 minutes daily can be helpful.
  
  
• Explore time-restricted eating. Research shows that fasting interventions may have a positive effect on anxiety and depression. Evolving research suggests that intermittent fasting has many benefits for cognitive function but larger studies are needed.
  
  
• Limit your alcohol intake. There’s an established association between heavy drinking and brain changes, cognitive impairment and dementia.
  
  
• If you smoke, consider quitting. You’ve no doubt heard about the dangers of smoking many times before, but did you know smokers have a higher risk of dementia than non-smokers, and stopping smoking, even when older, reduces the risk? Being mindful of secondary smoke is important too, as one study indicated that, in women aged 55-64 years, second-hand smoke exposure was associated with more memory deterioration, a risk that increased the longer they were exposed. We signpost to support to help you stop smoking in our article on ‘How does smoking cause cancer?’.
  
  
• Get your blood pressure checked every couple of years. Persistent high blood pressure (hypertension) in mid-life is associated with an increased risk of late life dementia, with an even higher risk if hypertension persists into later life. Aim for a systolic blood pressure of less than 130 mm HG in mid-life, something our article on lowering your blood pressure can help you do.
  
  
• Protect your head. All those warnings around driving and cycling carefully and sporting helmets and head protectors when you cycle or box are well founded. Traumatic Brain Injury (TBI) increased dementia risk in a huge study, a risk that was strongest in the first year following a TBI, but stayed high for over three decades. Mild TBI posed less risk than severe or multiple TBIs.
  
  
• Embrace hearing aids for hearing loss. In the first randomised controlled trial to examine whether a hearing intervention can reduce long-term cognitive change in cognitively healthy older adults, it was found that hearing intervention reduced 3-year cognitive change in older adults at increased risk for cognitive decline (although it had no effect in those at decreased risk for cognitive decline). A large cross-sectional study also found a decrease in cognition with every 10 decibel reduction in hearing, with mid-life hearing impairment being associated with increased shrinking of the temporal lobe, hippocampus and cortex in the brain. As hearing aids seemed to prevent this shrinkage, if you notice poor hearing, it’s best to get your hearing checked. Aids can take some getting used to, but you may find things improve, if you stick with them.
  
  
• Minimise exposure to air pollution. A systemic review of studies discovered that exposure to particulate matter, nitrogen dioxide, nitrous oxides, and carbon monoxide (CO) were all associated with increased dementia risk. Minimise your exposure where possible by going out earlier in the day when air quality tends to be better and sticking to quieter back streets to avoid areas where there’s heavy traffic. Keeping car windows closed, particularly if you’re driving in slow-moving traffic, and walking on the inside of pavements can also help as pollution levels are lower the further you are away from traffic. The Department for Environment Food & Rural Affairs produces a UK-wide pollution forecast every day, and for the next five days, for you to check.
  
  
• Stimulate your brain. Higher childhood education levels and lifelong higher educational achievement can reduce dementia risk. Research shows that some activities that stimulate the brain may also offer cognitive protection. These include doing crosswords later in life, (which was associated with delayed memory decline in people with dementia, independent of education levels), meditation, board games, and learning a new mentally-demanding skill, such as quilting, photography or a new language. These skills can also engage our senses, which could also preserve cognitive health. Therefore, engaging yourself and any children in your life with learning new skills or a new language can help as brain stimulation at all ages supports cognitive health. There are lots of brain stimulation tools and apps available to get you started.
  
  
• Seek help if experiencing depression. Depression is hard to bear, and seeking help can feel daunting for a number of reasons. However, with the diagnosed condition potentially more than doubling the risk for dementia, particularly in men, there’s even more reason to reach out for help from either your GP practice or self-refer to NHS Talking Therapies.
  
  
• Take care of your dental hygiene. A 2020 study found that people with gum disease and mouth infections were more likely to develop Alzheimer’s disease. Further studies are needed to confirm this finding.

You can also play a role in social and public health policies where possible. Any policies or initiatives that drive social, cognitive and physical activity for everyone across all age groups for the prevention of disease and social isolation can be great to participate in, especially as volunteering can help us feel happier on an individual level as well as benefit the wider population.

Reviewed by:

Anna Keeble MA BA Head of Content and Wellbeing Expert

Dr Claire Marie Thomas MRCGP DFSRH DTMH DipNLP MBChB BMedSci Medical Expert

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