Ultra-processed foods associated with an increased risk of dementia

What is ultra-processed food?
Ultra-processed foods are usually prepared from 5 or more ingredients, often using complex industrial processes. These foods are inexpensive to make, appetizing, high in added sugars, salt and fat, but low in protein, polyunsaturated fat and fibre. Some examples of ultra-processed foods include ready meals, chicken or fish nuggets, sausages, cookies, sweetened fruit yogurts, breakfast cereals, energy bars, soft drinks, sweets. Consumption of these energy-dense but nutritionally poor foods has increased considerably in recent decades, to the point that they now constitute more than 50% of the total dietary intake in some countries, such as the United States (58%).

Ultra-processed foods have been linked to adverse health effects such as cardiovascular disease, diabetes, cancer, depression, and all-cause mortality. Researchers from China and Sweden wondered if there was also an unfavourable association between the consumption of ultra-processed foods and the risk of dementia.

The researchers used data from the UK Biobank, a prospective study of 72,083 participants aged 55 or older who were followed for an average of 10 years. All participants showed no signs of dementia at the start of the study. After 10 years, 518 participants (0.72%) were diagnosed with dementia, including 287 participants (0.4%) who developed Alzheimer’s disease and 119 participants (0.17%) who developed vascular dementia. During the study, participants completed at least two detailed questionnaires about their diet, which allowed the researchers to estimate what percentage of the foods they consumed were ultra-processed. The researchers then divided the participants into four groups (quartiles) based on their level of consumption of ultra-processed foods.

Participants in the first quartile consumed an average of 225 g of ultra-processed foods (9% of daily food intake), while those in the top quartile consumed 814 g (28% of the daily intake). In order, soft drinks, sweets and ultra-processed dairy products were the most consumed ultra-processed foods. One hundred and five of the 18,021 participants in the first group who consumed the least ultra-processed foods developed dementia, compared to 150 of the 18,021 participants in the group (quartile) who consumed the most ultra-processed foods. After adjusting the data for age, gender, family history of dementia and heart disease, and other factors, it was estimated that for every 10% increase in daily intake of ultra-processed foods, participants had a 25% higher risk of dementia. The link was even stronger for vascular dementia (28%) compared to Alzheimer-type dementia (14%).

According to the same study, it was estimated that substituting 10% of ultra-processed foods with minimally or unprocessed foods (fruits, vegetables, legumes, milk and meat) is associated with a reduced risk of dementia by 19%. More concretely, an increase of 50 g/day of unprocessed food, equivalent to half an apple for example, replacing 50 g/day of ultra-processed food (equivalent to a chocolate bar or a slice of bacon) could reduce the risk of dementia by 3%. Thus, small changes in diet, requiring little effort, could make a big difference in a person’s risk of dementia.