Avocado on wholegrain toast isn't just a menu staple at trendy brunch spots — it could also be part of a Alzheimer’s and dementia busting diet.

Scientists examining the diet and cognitive abilities of over 3,000 Brits over the course of 70 years say they have found which foods eaten in childhood and younger adulthood help brain function in later life. 

They found diets consisting of unprocessed or less processed leafy green vegetables, beans, whole fruits and whole grains were the most protective.

Experts linked this to these foods' high levels of antioxidants and monounsaturated and polyunsaturated fats for boosting circulation to, and combating harmful substances in, the brain.

They found only seven per cent of people eating these kinds of diets early on in life recorded low cognitive ability, which can be a precursor to dementia, over the course of the study.

In dramatic contrast, 92 per cent of those who ate diets high in salt, added sugars and refined grains like white bread, suffered low cognitive ability in old age. 

Scientists based their findings on a long running British study that started in 1946 which tracked the diet and health of 3,059 Brits from the age of four to 75. 

Participants diets were examined at five points over the course of the study with their cognitive ability tested seven times. 

Cognitive ability is a term that reflects the strength of person's memory and thinking speed.

While some cognitive decline occurs naturally as we age it can also be a sign of conditions like dementia, with a quarter of those in with low cognitive ability in the study also showing signs of the condition. 

Authors of the new research, who presented their findings at the annual meeting of the American Society for Nutrition in Chicago, acknowledged that advice to eat more fruit and vegetables isn't new.

However, they added this research suggested eating these foods early in life had a more sustained protective effect on the brain than previously thought. 

Researcher Kelly Cara, an expert in nutrition from Tufts University in Boston, said: 'These initial findings generally support current public health guidance that it is important to establish healthy dietary patterns early in life in order to support and maintain health throughout life.'

'Our findings also provide new evidence suggesting that improvements to dietary patterns up to midlife may influence cognitive performance and help mitigate, or lessen, cognitive decline in later years.'

She added that while the findings have yet to be peer reviewed, they suggested a clear pattern in what foods appeared to help protect the brain.  

'Dietary patterns that are high in whole or less processed plant-food groups including leafy green vegetables, beans, whole fruits and whole grains may be most protective,' she said.

'Adjusting one’s dietary intake at any age to incorporate more of these foods and to align more closely with current dietary recommendations is likely to improve our health in many ways, including our cognitive health.'

What's more, researchers found that dietary patterns appeared to be established in childhood and then continue into later life, for better or worse. 

Fruit and vegetables are considered, in general, to be high in antioxidants which combat unstable atoms called 'free radicals' which are thought to damage cells.

Foods rich in monounsaturated fats help lower bad cholesterol in the blood and include avocados, peanut butter and nuts like almonds.

Polyunsaturated fats have similar benefits and, additionally, provide omega-6 and omega-3 fatty acids, essential fats that your body needs. Examples of foods high in polyunsaturated include oily fish like salmon, some nuts and tofu. 

Diets of the Brits in the study were assessed by the researchers as high or low quality based on American Government dietary guidelines.

These advise that adults, in general to eat at least two-and-a-half cups (an American kitchen measurement) of vegetables, two cups of fruit, 170g of grains, about 155g of leaner or vegetable-based proteins like beans and 27g (two tablespoons) of oils each day.

One example of what this would look like is an adult eating 88g of broccoli, two medium carrots, 33.5g of kale, 210g of apples, about four slices of wholemeal bread, and a chicken or fish fillet as well as 27g oil for cooking or salad dressing in one day. 

However, the exact quantities vary per specific food item and the calorie intake requirements of the adult in questions, which varies between men and women.

NHS guidelines for a healthy diet are broadly similar and encourage adults to eat five portions of a variety of fruit and veg each day, starchy carbohydrates such as bread or pasta ideally wholemeal, 30g of fibre a day, some lower fat dairy, for protein some beans, pulses, fish, eggs, leaner meat (including 2 portions of fish every week, one of which should be oily) and small amounts of unsaturated oils and spreads.

Adults are also encouraged to consume less than 6g of salt and 20g of saturated fat for women or 30g for men each day. 

Authors of the new research noted that the long-running nature of the study meant there had been some gaps and inconsistencies in data collection.

Around 944,000 people in the UK are thought to be living with dementia, while the figure is thought to be around seven million in the US.

Alzheimer's is the biggest cause of dementia affecting around six in ten of those with the condition.

It is thought to be caused by a build-up of amyloid and tau in the brain, which clump together and from plaques and tangles that make it harder for the brain to work properly.

Eventually, the brain struggles to cope with this damage and dementia symptoms develop.

The second most common form of dementia is vascular which is where there is a reduced blood flow to the brain such as stroke. 

Memory problems, thinking and reasoning difficulties and language problems are common early symptoms of the condition, which then worsen over time.

Alzheimer's Research UK analysis found 74,261 people died from dementia in 2022 compared with 69,178 a year earlier, making it the country's biggest killer.

WHAT SHOULD A BALANCED DIET LOOK LIKE? 

• Eat at least 5 portions of a variety of fruit and vegetables every day. All fresh, frozen, dried and canned fruit and vegetables count

• Base meals on potatoes, bread, rice, pasta or other starchy carbohydrates, ideally wholegrain

• 30 grams of fibre a day: This is the same as eating all of the following: 5 portions of fruit and vegetables, 2 whole-wheat cereal biscuits, 2 thick slices of wholemeal bread and large baked potato with the skin on

• Have some dairy or dairy alternatives (such as soya drinks) choosing lower fat and lower sugar options

• Eat some beans, pulses, fish, eggs, meat and other proteins (including 2 portions of fish every week, one of which should be oily)

• Choose unsaturated oils and spreads and consuming in small amounts

• Drink 6-8 cups/glasses of water a day

• Adults should have less than 6g of salt and 20g of saturated fat for women or 30g for men a day

Source: NHS Eatwell Guide