How diet can lower the risk of dementia

While there’s no cure for dementia, it’s not an inevitable part of ageing. And research shows that lifestyle changes, especially to our diet, can help reduce risk.

Key ways to decrease dementia risk

Fourteen different risk factors for dementia are within our power to tackle, and could potentially prevent almost half of all dementia cases worldwide, according to an in-depth report from medical journal The Lancet. Some of these risk factors – such as air pollution, less education, traumatic brain injury, loss of hearing and vision, depression and social isolation – are difficult to tackle by ourselves. But others – such as smoking, inactivity and excessive alcohol consumption – are very much within our control to change.

The Lancet report also identifies high blood pressure, diabetes, obesity and raised LDL or ‘bad’ cholesterol as conditions that increase dementia risk. All of these are influenced by diet, confirming our eating habits can play a major part in protecting us from dementia.

The role of diet in brain health

Our brain needs a steady supply of water and energy to function well. It’s why we struggle to concentrate or experience brain fog when we’re dehydrated or haven’t eaten for hours.

Many nutrients are also essential for a healthy, well-functioning brain. Iron, iodine and zinc are critical for cognitive functions such as learning, memory, reasoning and problem solving. Omega-3 fats, particularly DHA, are essential for brain development and function. B vitamins and vitamin C benefit psychological health, and together with potassium, magnesium, copper and iodine, support the nervous system.

It's unsurprising then that a University of Warwick study found a healthy, balanced diet is linked to better cognitive function and mental health, and more grey matter, which helps to process information in the brain.

Emerging research also links the trillions of microorganisms living in our large intestine, known as our gut microbiome, to brain health. The gut microbiome communicates with the brain via the gut-brain axis, affecting mood, cognition and potentially the development of diseases like dementia. Our gut microbiome can also trigger or suppress inflammation, which is central to many chronic conditions, including dementia. For example, short chain fatty acids, produced when gut bacteria break down fibre, appear to have anti-inflammatory effects. In contrast, inflammation may occur when the balance or diversity of gut bacteria is upset. Recent research also suggests specific gut bacteria may reduce or increase the risk of Alzheimer’s disease.

Make the change to a Mediterranean diet

Already known for its heart health benefits, there’s good evidence a traditional Mediterranean diet may protect against dementia, too. The Med Diet is made up of plenty of fruit, vegetables, wholegrains, pulses, healthy fats (such as oily fish, nuts, seeds and olive oil), with moderate amounts of dairy products, poultry, and eggs, and minimal red meat, butter, sugar, and processed foods. A recent UK study of 60,000 people found a Mediterranean diet lowered dementia risk by 23 per cent. The World Health Organization also recommends this diet to reduce the risk of cognitive decline and dementia.

The benefits most likely arise from the Mediterranean diet being packed with nutrients that support brain and gut health, aligning with general healthy eating guidelines, and protecting against high blood pressure, high cholesterol, type 2 diabetes and obesity – all of which increase dementia risk. For example, a Mediterranean diet has been shown to lower the risk of type 2 diabetes by 13 per cent.

More recently, the MIND diet (Mediterranean-DASH Intervention for Neurodegenerative Delay) – which combines key elements from the Mediterranean and DASH (Dietary Approaches to Stop Hypertension) diets – has gained popularity. Prioritising plant foods, fish and poultry, while restricting red meat and foods high in saturated fat and sugar, research has the MIND diet could significantly reduce the risk of Alzheimer’s disease – by 53 per cent if you adhere strictly to the diet, and 35 per cent for those following a moderate version.

How plant foods benefit your brain

Focussing diets on plants is key for reducing dementia risk, beginning with achieving five-a-day for fruit and veg, something only a third of adults manage. Research suggests eating an extra 100g of fruit and veg a day – just over one serving – lowers the risk of cognitive impairment and dementia by 13 per cent in older adults. Other good plant choices include wholegrains e.g. oats, wholemeal pasta and brown rice, pulses, potatoes, soya, nuts and seeds.

The benefits of plants most likely come from a combo of brain-friendly vitamins and minerals, fibre to support a healthy gut microbiome, and phytonutrients like polyphenols and carotenoids that have antioxidant and anti-inflammatory benefits. Instead of working in isolation, it’s more likely to be the range of nutrients in plants – and the variety of plants in our diet – that work together to support brain health.

Why you should eat more fish

Fish has also been well-studied for its potential role in preventing dementia. Oily fish such as salmon, mackerel, sardines and trout, are especially rich in omega-3 fats, which are important for both our heart and brain. Recent findings from the UK Biobank – a comprehensive health database – revealed higher intakes of omega-3 fats were linked to a lower risk of all types of dementia. A separate review of 35 studies also found those who ate the most fish had an 18 per cent lower risk of dementia. While more research is needed (other studies have been less positive) it makes sense to follow NHS advice to eat two servings (around 140g each) of sustainably sourced fish a week, including one oily fish.

Foods to avoid for better brain health

Foods high in saturated fat, sugar and salt contribute to high blood pressure, high cholesterol, type 2 diabetes and obesity, all risk factors for dementia and cardiovascular disease.

Start by limiting foods packed with saturates such as red and processed meat, full-fat dairy products, butter, cream, coconut and palm oils, cakes, biscuits, chocolate, and takeaways. Replace them with poultry, fish, eggs, pulses, soya, reduced-fat dairy, and vegetable oils and spreads, which provide healthier unsaturated fats.

While sugar itself doesn’t cause type 2 diabetes, sugary foods and drinks add extra calories to diets, which can contribute to weight gain and lead to obesity, a risk factor for dementia and type 2 diabetes, so it’s best to limit these. Want a sweet fix? Opt for fruit.

High salt intakes can raise blood pressure, a risk factor for strokes, which can cause vascular dementia. Avoid the salt pot, eat fewer salty foods such as processed meats, savoury snacks, canned soups, ready meals, pizzas and takeaways, and read food labels to help stay below the maximum recommended intake of 6g salt daily.

Research is increasingly linking ultra-processed foods (UPFs) to a higher dementia risk, possibly because of their low nutritional content and high levels of unhealthy fats, sugar and salt. Diets high in UPFs are also linked with obesity, type 2 diabetes and cardiovascular disease.

Finally, excessive alcohol intakes can damage parts of the brain involved in memory and communication, and increase blood pressure, heart disease and stroke. Limit alcohol to no more than 14 units a week – check your units at Alcohol Change UK.

The perfect diet to protect against dementia

Though studies suggest specific foods such as berries, leafy greens, nuts, olive oil, beans, coffee, tea, cocoa, garlic, and turmeric may offer brain benefits, no single food can prevent dementia. In contrast, a healthy, mainly plant-based diet like the Mediterranean diet supports brain health and protects against other health problems like cardiovascular disease, type 2 diabetes and obesity that increase dementia risk.

The key is to make plants – fruit, veg, potatoes, wholegrains, pulses, nuts, seeds and soya – the centrepiece of meals, and support them with smaller amounts of lean proteins like fish, eggs and reduced-fat dairy. Limiting saturated fats, sugar, salt, ultra-processed foods and alcohol is also important.

While the advice might be familiar, this type of diet is proven to keep both our brain and body healthy.

Juliette Kellow is a registered dietitian with a passion for food, nutrition and health. As a member of the British Dietetic Association, she has worked across the NHS, food industry and publishing sectors. Now a consultant, Juliette provides nutrition expertise and support for a diverse range of businesses from food brands, catering providers and restaurants to marketing agencies, media and health organisations. She regularly writes for magazines, newspapers and websites on food and health topics. Juliette is also the co-author of anti-aging book Eat Better Live Longer and Simply Nutrition For Complete Beginners, both published by DK.

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