Ultra-processed foods increase risk of anxiety and depression, study shows

Ultra-processed foods increase risk of anxiety and depression, study shows

A large population study shows diets high in ultra-processed foods are tied to poorer mental health, revealing biological markers that help explain the link.

In a study recently published in the journalNutrientsResearchers assessed the associations of ultra-processed foods (UPFs) and related metabolic signatures with mental disorders.

Mental disorders, including conditions such as anxiety, substance use disorder (SUD), and depression, are major contributors to global disease and the burden of global disability. Despite therapeutic advances in recent decades, the prevalence of mental disorders has remained, highlighting the need for complementary prevention strategies targeting modifiable risk factors.

Dietary habits play a crucial role in the development and progression of mental disorders. In particular, diets rich in omega-3 fatty acids, vegetables and fruits are associated with a reduced risk of mental disorders, while Western and anti-inflammatory diets rich in saturated fats and refined carbohydrates increase the risk. UPFs are mass-produced foods that go through multiple steps of processing and contain only limited contents of the whole food.

UPF intake has been steadily increasing, reflecting the globalization and urbanization of food systems. Despite substantial evidence implicating UPFs in mental health disorders, the underlying mechanisms remain unclear. The poor nutritional profile of UPFs, characterized by minimal fiber, higher calories, and excessive sugars, sodium, and saturated fats, has been associated with an increased risk of various chronic diseases.

About the study

In the present study, researchers examined associations of UPF intake and related metabolic signatures with mental disorders. Data from the United Kingdom Biobank (UKB), a large prospective cohort of over 500,000 participants, were used. The UKB collected extensive information on sociodemographic, biological factors and lifestyle. Participants were excluded if they were missing metabolomic measurements and dietary data or had previous mental disorder diagnoses.

Dietary intake data were obtained using a self-administered dietary assessment tool. High-throughput nuclear magnetic resonance spectroscopy was performed on plasma samples to quantify circulating metabolic profiles. The primary outcomes were total mental disorders, SUD, depressive disorders, or anxiety disorders. Secondary outcomes included 19 psychological symptoms.

These specific symptoms were unhappy, meaningless feeling, unhappiness with health, feelings of anxiety, premonition, excessive worry, irritability, restlessness, relaxation, appetite changes, anhedonia, uncontrolled worry, feelings of depression, fatigue, difficulty, concentration, feelings of inappropriateness, psychomotor changes, sleep problems and careful parenting.

Potential confounders included age, gender, body mass index (BMI), multiple deprivation index (IMD), prevalent diseases, healthy lifestyle factors, and waist-to-hip ratio (WHR). The metabolic features associated with UPF intake were identified using a net elastic regression model. Cox proportional hazards regression models examined the associations of UPF intake and associated metabolic signatures with mental disorders.

The base model was adjusted for age, gender, BMI and IMD. The multivariable model was additionally adjusted for lifestyle factors, prevalent diseases, and WHR. The mutually adjusted model included both UPF intake and its associated metabolic signature to analyze the independence of their associations with mental health outcomes. In addition, logistic regression models were used to examine associations with specific psychological symptoms.

Study workflow. This study enrolled a total of 30,059 UK biobank participants with a median follow-up of 12.6 years. (A) Study flow diagram - detailing participant selection, exclusion criteria and final cohort. (b) Definition of ultra-processed food intake (UPF) and composition of the constructed metabolic signature. (C) Cox proportional hazards regression models were used to assess the associations of UPF intake and its metabolic signature with incident risks of general mental disorder, depressive disorders, anxiety disorders, and substance use disorders with hazard ratios (HRS) and 95% confidence intervals (CIS). Logistic regression models were used to assess associations of UPF intake and its metabolic signature with the risks of specific psychological symptoms with estimated odds ratios (ORS) and 95% CIS. Subgroup analyzes were stratified by age and gender. (D) Mediation analyzes were applied to examine the mediating effect of the UPF-related metabolic signature. SUD indicates a substance use disorder.

Results

The study included an average of 30,059 participants aged 56.5 years. A total of 7,594 people developed mental disorders over a mean follow-up period of 12.6 years. Of these, 892, 865 and 1,300 subjects developed anxiety disorders, depressive disorders and SUD, respectively. The subjects with higher UPF intake were likely to be younger and have higher body BMI, BMI, higher levels of deprivation (lower socioeconomic status based on IMD scores), and unhealthy lifestyles.

Net elastic regression identified 91 metabolites associated with UPF consumption, spanning various biochemical categories including fatty acids, lipoproteins (such as HDL cholesterol ratios), glucose-related metabolites, and amino acids (such as valine). Participants with high UPF intake had a higher risk of general mental health disorders, anxiety disorders, depressive disorders, and SUD than those with low UPF intake. Similarly, a higher metabolic signature of the UPF compound was associated with higher risks of all four mental health outcomes. Subgroup analyzes suggest that these associations may be stronger in certain groups. For example, the association between the metabolic signature and SUD in women and the associations for UPF intake with SUD and the metabolic signature with depression and anxiety were stronger in those under 60 years of age.

Mediation analysis showed that the UPF-linked metabolic signature partially mediated the associations between UPF consumption and psychological disorders. In addition, higher intake of UPFs was associated with increased risks of various sympathetic symptoms, including suicidal ideation, anxiety, and health unhappiness. Conversely, the UPF-linked metabolic signature showed no significant associations with mental health symptoms in the overall population, although subgroup analyzes revealed associations between the signature and symptoms such as unhappiness with health and depressive feelings, particularly in those under 60 years of age.

Associations of ultra-processed food intake and its metabolic signature with mental health symptoms and stratified by age. Symptoms included three categories, namely subjective well-being (3 items), PHQ-9 (9 items), and GAD-7 (7 items). Logistic regression models were used to assess the associations of UPF (ultra-processed foods) intake and its metabolic signature with the risks of specific psychological symptoms. (A) For UPF intake. (b) For metabolic signature. Results were presented with odds ratios (ORS) per 10% increment for UPF intake and ORS per SD increment for metabolic signature. Colors indicate significance levels after false discovery rate correction (significant blue and non-significant gray).

Conclusions

Overall, UPF intake was significantly associated with higher risks of general mental health disorders, anxiety disorders, SUD, and depressive disorders. The UPF-related metabolic signature was also independently associated with increased risk of these mental disorders. It also partially mediated the association between UPF consumption and psychiatric outcomes. The researchers noted limitations including the study population, predominantly white UK residents, the reliance on self-reported data, the cross-sectional nature of the metabolite measurement and the potential for residual confounding, meaning the results should be interpreted with caution. Therefore, the results suggest that improving diet quality and reducing UPF consumption may help maintain mental well-being.

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