The study, published in the online issue of Neurology, the medical journal of the American Academy of Neurology, also showed that replacing ultra-processed foods in a person’s diet with unprocessed or minimally processed foods was associated with a lower risk. The study does not prove that ultra-processed foods cause dementia, it only shows an association, researchers stressed.
Ultra-processed foods ‘diminish’ quality of diet
Ultra-processed foods are high in added sugar, fat and salt, and low in protein and fibre. They include soft drinks, salty and sugary snacks, ice cream, sausage, deep-fried chicken, yogurt, canned baked beans and tomatoes, ketchup, mayonnaise, packaged breads and flavoured cereals.
“Ultra-processed foods are meant to be convenient and tasty, but they diminish the quality of a person’s diet,” said study author Dr Huiping Li of Tianjin Medical University in China. “These foods may also contain food additives or molecules from packaging or produced during heating, all of which have been shown in other studies to have negative effects on thinking and memory skills. Our research not only found that ultra-processed foods are associated with an increased risk of dementia, it found replacing them with healthy options may decrease dementia risk.”
During the study, researchers identified 72,083 people from the UK Biobank, a large database containing the health information of half a million people living in the United Kingdom. Participants were aged 55 and older and did not have dementia at the start of the study. They were followed for an average of 10 years. By the end of the study, 518 people were diagnosed with dementia.
Participants filled out at least two questionnaires in the duration of the research period. This included details about what they ate and drank the previous day. From this data, researchers determined how much ultra-processed food people ate by calculating the grams per day and comparing it to the grams per day of other foods to create a percentage of their daily diet.
The researchers then divided participants into four equal groups from lowest percentage consumption of ultra-processed foods to highest. On average, ultra-processed foods made up 9% of the daily diet of people in the lowest group, an average of 225 grams per day, compared to 28% for people in the highest group, or an average of 814 grams per day. One serving of items like pizza or fish fingers is equivalent to 150 grams. The main food group contributing to high ultra-processed food intake was beverages, followed by sugary products and ultra-processed dairy, the study revealed.
In the group with the lowest consumption of ultra-processed food, 105 of the 18,021 people developed dementia. This compares to 150 of the 18,021 people who ate the largest amounts of ultra-processed products.
After adjusting for age, gender, family history of dementia and heart disease and other factors that could affect risk of dementia, researchers found that for every 10% increase in daily intake of ultra-processed foods, people had a 25% higher risk of dementia.
‘Small and manageable changes may make a difference’
The study authors also wanted to look at what happens if you reduce your intake of ultra-processed foods and replace it with healthier items. They used study data to estimate what would happen if a person substituted 10% of ultra-processed foods in their diet with unprocessed or minimally processed foods, like fresh fruit, vegetables, legumes, milk and meat.
The result? The substitution was associated with a 19% lower risk of dementia.
“Our results also show increasing unprocessed or minimally processed foods by only 50 grams a day, which is equivalent to half an apple, a serving of corn, or a bowl of bran cereal, and simultaneously decreasing ultra-processed foods by 50 grams a day, equivalent to a chocolate bar or a serving of fish sticks, is associated with 3% decreased risk of dementia,” said Dr Li. “It’s encouraging to know that small and manageable changes in diet may make a difference in a person’s risk of dementia.”
Dr Li noted that further research is needed to confirm the findings.
The complexity of defining ultra-processed foods
While the findings point to a noteworthy difference in health outcomes between those of us who eat the most, and least, amounts of ultra-processed food and drink, there is some difficulty in pinning down exactly what we mean by ‘ultra-processed’.
As Dr Maura Walker of Boston University observed: “While nutrition research has started to focus on food processing, the challenge is categorizing such foods as unprocessed, minimally processed, processed and ultra-processed.”
Dr Walker, who wrote an editorial accompanying the study, elaborated: “For example, foods like soup would be classified differently if canned versus homemade. Plus, the level of processing is not always aligned with diet quality. Plant-based burgers that qualify as high quality may also be ultra-processed. As we aim to understand better the complexities of dietary intake, we must also consider that more high-quality dietary assessments may be required.”
The study was funded by the National Natural Science Foundation of China.
‘Association of Ultraprocessed Food Consumption With Risk of Dementia A Prospective Cohort’
Authors: Huiping Li, Shu Li, Hongxi Yang, Yuan Zhang, Shunming Zhang, Yue Ma, Yabing Hou, Xinyu Zhang, Kaijun Niu, Yan Borne, Yaogang Wang