September 2, 2026, 12:50 pm | Read time: 7 minutes
Ultra-processed foods are produced 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 in more detail: the connection 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. FITBOOK spoke with one of the study’s authors.
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 idea 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 connection between the consumption of ultra-processed foods and depressive symptoms.2
Researchers from Justus Liebig University Giessen have now examined more closely whether and which components of ultra-processed foods are associated with the later occurrence 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, 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 possible 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.
Also interesting: Why sugar from drinks is particularly unhealthy
Results
The average follow-up period was about 10.7 years. All participants combined were observed for approximately 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 Notable: 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 among the individual substances examined. Of the 39 markers studied, twelve 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.
Study Author Puts the Results into Perspective for FITBOOK
Study author Dr. Nathalie Eise finds one aspect of the study particularly insightful: “Not all of the ultra-processing markers examined” were associated with an increased risk of depression. “Ultra-processed foods are often lumped together. But these findings show that differentiation and a look at the ingredient list can be quite useful.”
Flavors, colorings, and sweeteners, in particular, showed a connection with an increased risk of later depression. In contrast, the researchers found no statistically significant connection in five of the ten categories examined. There were also differences within the individual substance groups: Seven of the ten sweetener markers studied were dose-dependently associated with the later occurrence of depression. Flavors and colorings also showed an increased risk, with fructose showing a linear relationship.
Explanations for the Observations
But how could the observed connections come about? “There are plausible explanations for flavors and sweeteners,” Eise explains. “For example, it is discussed that these can lead to overeating and thus to weight gain.” For sweeteners, another possible mechanism is added: “For sweeteners, a change in the gut microbiome is also discussed. Such changes could, in turn, be relevant for the development of depression.” Additionally, “direct effects of individual additives on neurochemical signaling pathways are conceivable.”
At the same time, the study author cautions against overinterpreting the findings. “Whether and to what extent such mechanisms actually explain the connections we observed in humans is still unclear.” The results should not be understood as evidence that flavors, colorings, or sweeteners cause depression. “Rather, they show that these ingredients should be examined more closely in further experimental and clinical studies.”
Which Additives Affect Mortality
These Foods Can Increase Dementia Risk by 58 Percent
Significance of the Study–for Consumers and Research
A general recommendation to avoid individual additives cannot yet be derived from the results. “Our results alone are not enough to recommend generally avoiding individual additives,” says Eise. At the same time, she sees no harm in “looking more closely at the ingredient list when shopping and, if there is a comparable alternative, choosing products without flavors, sweeteners, or colorings.”
There are often simple alternatives within the same product category. Eise cites strawberry yogurt as an example: “There are products with added flavors and colorings–and others that do without these additives.” Based on these findings, her research group has also developed a free nutrition program called Neatic, which aims to support the reduction of flavors, sweeteners, and larger amounts of free sugars in everyday life.
For research, the study provides an approach to examine individual components of ultra-processed foods more closely in the future. In particular, flavors, colorings, and sweeteners should be given more attention.
Limitations
One should also note the study’s limitations. Among other things, the participants’ diets were recorded using 24-hour dietary questionnaires. Such snapshots can only partially reflect long-term dietary 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’ data. Thus, a modeled estimate is presented, not a direct analysis of actually consumed foods.
In summary, as is usual with observational studies, it can be said that the study shows connections but cannot make any statements about whether certain 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 therefore see a need for further research, particularly on the possible biological mechanisms.