The diet that could cut dementia risk by almost 25%

A major new study suggests that one particular diet could make you far less likely to develop dementia. Sue Quinn speaks to the experts to find out how it works.

Almost one million people in the UK live with some form of dementia.

Worldwide, cases are expected to almost triple from 2019’s figure of 57 million to 153 million by 2050, in line with the growth and aging rates of the global population.

There’s no cure for the different brain diseases that cause dementia. However, a major new study – the largest of its kind – suggests that a certain type of diet can protect against the condition.

A team of scientists from leading universities in the UK, Australia and Sweden analysed data from 60,000 British people to find out whether a Mediterranean diet offered protection against dementia. Using information from the UK Biobank, they measured participants’ adherence to a Mediterranean diet and how many developed dementia over the course of a decade.

“We found that the individuals whose diets more closely matched the features of a Mediterranean diet had a much lower risk of developing dementia,” says Dr Oliver Shannon, a lead author of the study and a lecturer in nutrition and ageing at Newcastle University. “On average, people who had a high (compared to low) adherence to a Mediterranean diet had about a 23% lower risk of developing dementia.”

Even those who have a higher chance of developing the condition because of their genetic risk could benefit by roughly the same rate, the researchers found.

So, what is a Mediterranean diet exactly? Broadly speaking, it includes lots of fruits, vegetables, legumes and pulses, as well as nuts, whole grains, fish and unsaturated fats such as olive oil. It also involves moderate amounts of dairy (cheese and yoghurt mostly) and small quantities of meat and saturated fat, such as butter.

There are various technical definitions of a Mediterranean diet, which can slightly differ. So, to make this study as accurate as possible, scientists used two types of scoring systems (Mediterranean Diet Adherence Screener and Mediterranean diet Pyramid).

Shannon says the findings suggested the following offered the most potential protection against dementia:

• Olive oil as the main cooking fat
• At least 400g of vegetables per day (5 x 80g servings), with at least 200g of this consumed raw or as salad
• At least 240g of fruit per day (3 x 80g servings), including no more than 100ml of natural fruit juice
• Less than 100–150g of red or processed meat per day
• Less than 12g of butter or margarine per day
• Fewer than one sweet, fizzy drink per day
• One small glass of wine (125ml) per day
• At least 3 x 150g servings of legumes each week
• At least 3 x 100-150g servings of fish or shellfish each week, ideally including at least one portion of oily fish
• Fewer than three servings per week of shop bought cakes, cookies, pastries, or desserts
• At least 3 x 30g servings of nuts per week
• Consuming more poultry than red meat
• At least two servings each week of dishes made with a sauce base of tomato, onion, leek, or garlic and simmered with olive oil

No single food on its own reduced the risk of dementia, Shannon says. Rather, they all probably worked together.

“The data suggests that all of the components are important in their own right. It’s an amalgamation of all the different benefits of lots of different things.”

The study looked at the impact of the Mediterranean diet on dementia as a whole, as opposed to separating out specific types such as Alzheimer’s disease. “But there are other studies which have suggested eating a Mediterranean diet is probably good for reducing Alzheimer’s risk,” Shannon points out. “We don't have as much evidence for other sub-types of dementia like vascular dementia, but we might expect that a Mediterranean diet would help protect against them as well.”

How does this diet protect against dementia?

Prof David Lewellyn from the University of Exeter Medical School says the UK Biobank study is one of many that suggests a link between diet and dementia. Plenty of other studies have also found that diets which incorporate the Mediterranean diet or are very similar – such as DASH and MIND – may have protective effects.

While scientists don’t fully understand why these diets benefit brain health, there’s a common theme among them all which gives us some clues.

“These diets are all high in fruits, vegetables, whole grains and healthy fats,” Lewellyn says. “They are also low in processed foods, red meat and saturated fats.”

It is known that chronic conditions like cardiovascular disease and type 2 diabetes increase the risk of developing dementia. One theory is that because a Mediterranean diet reduces the risk of developing these conditions, it also reduces the risk of dementia, Shannon says.

Some research findings also show that some of the foods involved in a Mediterranean diet have anti-inflammatory and antioxidant effects. This is because they contain compounds that protect against cell damage, and so could benefit the brain directly.

“There have been some studies suggesting that consuming a Mediterranean diet might help slow the rate of brain atrophy [degeneration] over time,” Shannon says.

Can diet slow the onset of dementia?

Eating healthily from a young age may carry important benefits, “because the brain is still developing during childhood and adolescence,” Lewellyn explains. “Eating a healthy diet during these developmental years probably helps to lay the foundation for a healthy brain later in life.”

But it's never too late to start: “Even small changes to your diet in later life may help to protect against dementia.”

That said, there’s currently no evidence that changing our diet will slow or halt the progression of dementia once it’s been diagnosed. And while mounting research suggests diet may reduce your chances of developing it, there are no guarantees.

“It is not possible to conclude definitively that changing your diet will necessarily reduce your own individual risk of dementia,” Lewellyn says. Genetics, lifestyle and other factors also play an important role.

“However, making improvements to your diet is likely to improve your health and wellbeing and is a promising strategy to reduce your risk.”

How easy is a Mediterranean diet to follow?

The Mediterranean approach to eating is popular and involves a wide range of foods that many people enjoy. That said, it can be challenging to eat this way all the time if you're unable to cook most of your meals from scratch. Luckily, there's plenty of advice available online, which can help you make it work for you.

With its emphasis on fruit and vegetables, grains, nuts, seeds and seafood, the Mediterranean diet might seem costly, but as Shannon points out, “that can be partly offset by choosing frozen and tinned varieties of these foods.”

To create Mediterranean dishes on a budget, you could turn tinned pulses into dishes such as a chilli bean stir fry or a bean salad. It could also help to make the most of wallet-friendly ingredients such as red lentils which are widely used in Mediterranean cooking. Tinned fish is an ideal way to make sure you’re including seafood in your meals without bumping up the cost of your grocery shop, and can be used in quick, simple dishes like sardines and kale with pasta.

To boost your nut and seed intake, keep jars of them on the kitchen worktop and sprinkle into your cereal, soup, salads and casseroles or simply slather a nut butter onto a slice of wholemeal toast.

Originally published May 2023