Ultra-processed foods promote dementia

The ELSA-Brasil study recruited senior civil servants in six cities in this country from 35 to 74 years oldwith a followed between 2008 and 2019 ; data collection was carried out in three waves spaced 4 years apart (2008-2010, 2012-2014, 2017-2019).

A total of 10,775 participants were included in the analysis, following excluding people who reported extreme values ​​of caloric intake (i.e. < 600 kcal/j ou > 6,000 kcal/d) and those taking medications that may interfere with cognitive functions. They were followed for a median of 8 years. Their average age at the start of the study was 51,6 ans, there were 54.6% women, the average BMI was 26.9 and ultra-processed foods accounted for an average of 27% of daily energy intake.

Food consumption was assessed thanks to a validated questionnaire of 114 items (Food Frequency Questionnaire), from which the researchers calculated the proportion of calories coming from ultra-processed foods on the total daily energy intake of each participant. They then divided the cohort into four groups : people for whom these products represented less than 19.9% ​​of intake (reference group); those for whom consumption was between 20% and 26.7%, then between 26.8% and 34.1% and finally between 34.2% and 72.2%.

Evaluation of cognitive functions was carried out up to three times every 4 years. Memory abilities were tested via immediate and distant memories and word recognition, with tests of Consortium to Establish a Registry for Alzheimer Disease. The evaluation of the executive functions was made thanks to the Trail Making Test B estimating visual attention and task switching abilities.

Finally, the analysis controlled for confounding factors such as age, gender, clinical variables (BMI, metabolic diseases, etc.) but also lifestyle and socio-economic level and education as well as ethnicity, which can influence both eating habits and cognitive performance (in this respect, the cohort was balanced and representative of the Brazilian population with approximately half of white people and more than 40% of people of African or mestizo origin).

Results : following a median follow-up of 8 years, the participants of the three groups that consumed the most ultra-processed foods (> 19.9% ​​of daily intake) had a28% faster cognitive decline than those in the reference group. As for the decline in executive functions, it was 25% faster.

People under 60 were the most affected by this association, while it was not found in the over 60s. Moreover, poor overall eating habits increased this correlation : people with low food scores (indicating an unhealthy diet) and consuming > 19.9% ​​of these products had a faster cognitive decline than those consuming less, while no significant association was found between the percentage of ultra-processed food consumed and cognitive decline in participants with overall healthy diets.

Several hypotheses might explain these associations: reduction in the volume of the left hippocampus and the gray matter linked – according to certain neuroimaging studies – to contemporary Western diets; systemic inflammation may be induced by the consumption of ultra-processed foods… On the contrary, healthy diets have been associated with a greater volume of white and gray matter and with lower levels of oxidative stress and inflammation (which might also explain potentially the protective effect of a healthy diet observed in this study).

These results converge in particular with those of a study on the UK Biobank cohort which found a link between the consumption of ultra-processed foods and an increased risk of dementia and Alzheimer’s in people over 55, while by extending these associations to younger age groups. Hence the importance of reducing the consumption of these products for young adults and those of middle age, in primary prevention therefore, conclude the authors.