Eating too much junk can give you dementia! Another study says ultra-processed foods harm the brain

A diet of fizzy drinks, chips and cookies isn’t just bad for the waistline.

Gorging on too much junk food can also increase your risk of developing dementia, scientists say.

The study tracked more than 70,000 middle-aged for a decade to try and tease out the effects of a diet heavy in ultraprocessed snacks.

Junk food fanatics were 43 per cent more likely to be struck down with the memory-robbing condition, compared to those who ate the least.

Lovers of ultraprocessed foods consumed 810g a day, on average — the equivalent weight of three-and-a-half Big Macs, while the least ate just a quarter of that (225g).

Although the study doesn’t prove a bad diet causes dementia, it adds to the ever-growing pile of evidence linking the two together. 

Chinese researchers also found swapping just one chocolate bar a day for a bowl of cereal effectively cut the risk of getting dementia by 3 per cent.

Lead author Dr Huiping Li, from Tianjin Medical University, said: ‘It’s encouraging to know small and manageable changes in diet may make a difference in a person’s risk of dementia.’

A study of more than 70,000 elderly Britons by Chinese researchers found that those who ate the most ultra-processed junk food were 43 per cent more likely to develop dementia than those who ate the least. The biggest junk food fanatics ate 810g per day, the equivalent weight of wo-and-a-half pizzas, while the least ate 225g per day — around four Mars bars


Meals should be based on potatoes, bread, rice, pasta or other starchy carbohydrates, ideally wholegrain, according to the NHS

Meals should be based on potatoes, bread, rice, pasta or other starchy carbohydrates, ideally wholegrain, according to the NHS

• 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  

Ultra-processed foods are high in added fat, sugar and salt, low in protein and fibre and contain artificial colourings, sweeteners and preservatives.

Ready meals, ice cream, sausages, deep-fried chicken and ketchup are some of the best-loved examples.

They are different to processed foods, which are processed to make them last longer or enhance their taste, such as cured meat, cheese and fresh bread. 

Dr Li’s team examined the health records of 72,083 over-55s from the UK Biobank — a database of medical and genetic records of half a million Britons, who regularly provide information on their lifestyle, as well as blood and urine samples.

Over the course of the study, the participants completed at least two questionnaires about what they ate and drank the previous day.

The experts used this to calculate the volunteers’ daily food intake in grams and what proportion of this was junk food. 

Participants were then divided into four equally-sized groups based on how much of their diet was made up of ultraprocessed food, ranging from the lowest (225g/day, or nine per cent of their intake) to highest (814g/day, 28 per cent of their diet).

One slice of pizza or a portion of fish fingers was listed as being equivalent to 150g of ultra-processed foods. 

None of the participants had dementia at the start of the study. But a decade later, 518 had been diagnosed.

The results, published in the scientific journal Neurology, show 105 of people who ate the least among of junk food developed dementia.

The figure jumped to 150 of those who ate the most junk food were diagnosed with the conditions.

After accounting for established risk factors such as age, gender and family medical history, researchers spotted that every 10 per cent increase in daily junk food intake increase the risk of dementia by 25 per cent.

Meanwhile, for every 10 per cent of processed food substituted with healthy options, such as fruit, vegetables and milk, the risk of dementia fell by 19 per cent.

The team noted that dementia was confirmed through hospital records and death certificates, rather than primary care data, so some milder dementia cases may have been overlooked. 

And the findings do not mean junk food causes dementia. 

But ultra-processed foods often contain additives as well as molecules from packaging which have been shown to harm thinking and memory skills, Dr Li said.

‘Our research not only found ultra-processed foods are associated with an increased risk of dementia, it found replacing them with healthy options may decrease dementia risk,’ he said.

Junk food is ‘meant to be convenient and tasty’ but they ‘diminish the quality of a person’s diet’, he added. 

Dozens of studies have shown that following a poor diet raises the risk of developing heart or circulatory disease, high blood pressure and cholesterol levels, which in turn raises the risk of dementia.

Some 900,000 people in the UK and 5.8million in the US are living with dementia.

Dr Rosa Sancho, head of research at Alzheimer’s Research UK, said experts are still puzzled as to why people who eat ultra-processed foods are at a higher risk.

But it could be down to a lack of key nutrients, or that the diets lead to high blood pressure or inflammation, which can be bad for brain health, she said.

Dr Sancho added: ‘While the researchers have run a careful analysis, it’s impossible to be certain that this link is down to differences in diet rather than other lifestyle factors that may go along with eating more ultra-processed food.

‘The research took the total calorie intake of the participants into account, so the link shouldn’t be a result of people who eat ultra-processed foods simply eating more.

‘We know that what is good for our heart health is also good for our brain health, so we encourage people to stay active, socially connected and involved in activities and hobbies that they enjoy. It is also important to maintain a healthy balanced lifestyle.’