September 2, 2026, 12:50 pm | Read time: 6 minutes
Ultra-processed foods are made through many processing steps and the use of various industrial substances. They have long been considered potentially harmful to health. German researchers have now examined a specific aspect more closely: the link between the consumption of these foods and the occurrence of depression. They were particularly interested in which components might play a role. The study’s results highlight flavors and colorings, among other things.
Ultra-Processed Foods Promote Diseases
Research links frequent consumption of ultra-processed foods (UPF) with an increased risk of chronic diseases and higher mortality. According to a recent series of studies, ultra-processed foods can also affect nearly all organ systems; FITBOOK reported.1
A connection is also emerging for mental health. The fact that diet can be linked to mental health and depression through the so-called gut-brain axis is not new. Previous studies have already found a link between the consumption of ultra-processed foods and depressive symptoms.2
Researchers at Justus Liebig University Giessen have now examined more closely whether and which components of ultra-processed foods are associated with the later onset of depression.3 The results of the new study paint a more nuanced picture.
Details of the Study
This was a population-based, prospective cohort study based on the UK Biobank. Participants were enrolled in the UK Biobank between 2006 and 2010 in the United Kingdom. To participate in the present study, they had to have completed at least one web-based 24-hour dietary questionnaire (Oxford WebQ).4 After matching with predefined exclusion criteria, 171,818 participants remained for the main analysis, with an average age of 58.5 years.
For the study, researchers defined products in Group 4 of the NOVA classification system as ultra-processed foods. However, the classification of such foods is not always clear-cut, as it can depend on the interpretation of ingredient lists. To refine identification, the researchers used so-called markers for ultra-processed foods (MUPs). These include flavors, colorings, and sweeteners, as well as ingredients not typically used in home cooking.
Overall, the team examined ten MUP categories and 39 individual MUPs. According to the authors, they were the first to systematically analyze the relationships of these categories and individual markers with newly occurring depression.
Ultra-Processed Foods in the Participants’ Diets
The Oxford WebQ recorded the foods and beverages participants consumed the previous day. To determine the MUPs, ingredient lists from 2,459 different commercial products were examined. These came from the two leading British food retailers, Tesco and Sainsbury’s. For each food, the likelihood of a specific marker’s presence was estimated based on the examined products.
The researchers then calculated the proportion of each marker in the total food consumption. If participants completed multiple dietary questionnaires, the researchers averaged the results.
First Occurrence of Depression Due to UPF
Depressions were recorded as newly occurring diagnoses according to the International Statistical Classification of Diseases and Related Health Problems (ICD-10). Depressive episodes (F32) and recurrent depressive disorders (F33) were considered.
To investigate how the consumption of ultra-processed foods and the occurrence of depression were related, the researchers used statistical Cox regression models. They considered various potential influencing factors, such as age, alcohol consumption, body mass index, physical activity, smoking, income, and education level.
On average, the participants’ diets consisted of about 19.9 percent ultra-processed foods. Among the MUP categories examined, the average proportion for flavors was the highest at 13.5 percent, followed by processing aids at 7.6 percent and colorings at 5.6 percent.
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Results
The average follow-up period was about 10.7 years. Combined, all participants were observed for about 1.8 million years. During this time, researchers recorded 5,424 new cases of depression.
For the total proportion of ultra-processed foods, a U-shaped relationship with depression risk was initially observed. The lowest estimated risk was at a proportion of about 16 percent of total food consumption. Beyond that, the risk increased with a higher proportion of ultra-processed foods. At a proportion of 30 percent, it was 16 percent higher, at 40 percent, 32 percent higher, and at 50 percent, 41 percent higher–each compared to the range of the lowest estimated risk.
Particularly Noticeable: Colorings, Flavors, and Sweeteners
The connection was particularly pronounced for three categories of markers for ultra-processed foods: colorings, flavors, and sweeteners. For colorings, the highest hazard ratio of 1.49 was observed at a proportion of 20 percent, followed by flavors with 1.46 at a proportion of 40 percent, and sweeteners with 1.45 at 20 percent.
Differences were also observed in the individual substances examined. Of the 39 markers studied, 12 were statistically significantly associated with the occurrence of depression. These included seven sweeteners–such as acesulfame, aspartame, erythritol, saccharin, steviol, sucralose, and xylitol–fructose, and a thickening agent. For three other substances–foaming agents, maltodextrin, and gluten–an inverse relationship was observed. No statistically significant association was found for 22 markers.
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What Do the Results Mean?
The results indicate that the term “ultra-processed” alone may be too imprecise to predict the potential health effects of different foods, as it describes a large group of foods. While flavors, colorings, and sweeteners seemed to have a promoting effect on depression, the study authors found no statistically significant association for five of the ten categories examined.
Significant differences were also observed in the individual components. Seven of the ten sweetener markers studied were dose-dependently associated with the later onset of depression. An increased risk was also observed for flavors and colorings, while a linear relationship was observed for fructose.
For research, the study provides a good starting point to examine individual components of ultra-processed foods more specifically in the future. According to the authors, flavors, colorings, and sweeteners should be given more attention in further studies and potential interventions.
Limitations
However, the study’s limitations should also be noted. Among other things, the participants’ diets were recorded using 24-hour dietary questionnaires. Such snapshots can only partially reflect long-term eating habits, and the reliability of self-reports is always questionable.
Furthermore, the researchers did not directly determine the markers for ultra-processed foods (MUPs) in the consumed products. Instead, they analyzed ingredient lists from 2,459 commercial products and applied the probabilities derived from them to the participants’ reports. Thus, a modeled estimate is presented rather than a direct analysis of actually consumed foods.
In summary, as is usual with observational studies, the investigation shows associations but cannot determine whether specific components of ultra-processed foods actually cause depression. Despite statistical adjustments, it cannot be ruled out that other unconsidered factors influenced the results. The authors see a need for further research, particularly on possible biological mechanisms.