FLAVOURS, colouring agents, and sweeteners commonly found in ultra-processed foods (UPFs) have been linked to an increased risk of developing depression, according to new research.
Typically rich in fat, salt, and sugar but low in levels of essential macronutrients like proteins and dietary fibres, UPFs have gained popularity in recent years due to their convenience and wide availability.
Now, beyond previous evidence that they could be linked to increased risk of obesity, high cholesterol, cardiovascular disease, and type 2 diabetes, more resent research shows that UPFs may be having an effect on our mental health too.
The large prospective study examined whether individual markers of ultra-processed food (MUPs) were associated with incident depression, defined as a new diagnosis or first-time development of depression.
Rather than treating all UPFs as a single category, researchers investigated 10 categories and 39 specific markers to determine whether particular ingredients may be driving previously reported associations between UPF consumption and depression.
To do so, researchers analysed data from 171,818 UK Biobank participants who had completed at least one web-based 24-hour dietary questionnaire.
Participants with pre-existing depression were excluded, and the cohort was followed for an average of 10.7 years, during which 5,424 new cases of depression were recorded.
Among the 10 MUP categories examined, flavour, colouring agents, and sweeteners all showed significant associations with depression risk, which changed depending on the level of intake.
It was found that participants whose foods containing flavouring accounted for 40% of their total food intake had a 46% higher relative risk of depression when compared with the intake associated with the lowest observed risk.
When foods containing colouring agents made up 20% of a person’s total food intake, their relative risk of depression was 49% higher. When foods containing sweeteners accounted for 20% of their total intake, their relative risk was 45% higher.
In contrast, five categories, including flavour enhancers, processing aids, modified starches, varieties of sugar, and modified oils, each showed no significant association with depression.
When researchers examined individual markers, seven of the 10 sweetener types studied showed significant dose-dependent associations with depression.
These included acesulfame, aspartame, erythritol, saccharin, steviol, sucralose, and xylitol – all commonly found in diet sodas, sugar-free chewing gum, and tabletop sweetener packets, amongst other products like low-sugar baked goods and flavour syrups.
Higher fructose intake was also associated with an increased risk of developing depression, while other ingredients showed more complex patterns of association, with some even linked to a lower risk.
The findings remained largely consistent across multiple sensitivity analyses, including after accounting for diet quality which varied between participants and excluding people who developed depression within the first two years of follow-up from the study.
The researchers suggest the findings could help refine how the health effects of UPFs are investigated. Rather than assuming all markers of ultra-processing carry the same risk, future research may benefit from focusing on specific ingredients like types of sweeteners or colourings.
They also suggest that there could be notable links between mental health and the consumption of foods that contain these ingredients.
Possible reasons for this include effects on brain signalling, metabolic health, obesity, and the gut microbiome. However, the researchers of the study stressed that the mechanisms remain unclear and require further investigation.
Importantly, the observational nature of the study means it cannot establish that these ingredients definitively cause depression. Dietary intake was also self-reported, and the presence of individual markers was estimated rather than measured directly in foods consumed by each participant.
The authors conclude, however, that flavourings, colouring agents, and sweeteners may warrant particular attention in future and interventions examining the relationship between UPFs and mental health.
The research also stands as compelling evidence to support continued research into the negative effects of UPFs, both on our physical and mental health.
Reference
Blumenthal A K et al. Relationship between 39 dietary markers of ultra-processed food and incident depression: evidence from the prospective UK Biobank cohort study. Eur J Nutr 65, 238. 2026.
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