Ultra-processed food consumption is linked to quality of life and mental distress among university students

Introduction

From young to adulthood, university acts as a transitional phase that helps to develop abilities essential for future careers (Uzdil, Kılıç & Özenoğlu, 2021). This can be difficult due to several reasons, including peer competition, academic performance pressure, modifications in workload and support networks, changes in living conditions, and extended separation from family (Ramón-Arbués et al., 2022). The incidence of mental distress indicators, including depression and anxiety, among university students ranges from 18% to 50% (Mutinta, 2022; Ramón-Arbués et al., 2022). Mental health impairment is more pronounced among university students, and both physical and mental health impairments are inversely correlated with health-related academic success (Wilks et al., 2020).

University students may have limited access to healthy, home-cooked meals and may depend on readily available, quickly consumable items from vending machines. Additionally, university canteens predominantly offer energy-dense snacks (Bos et al., 2018; Racine et al., 2022). Because of budget limitations and prolonged study periods, students frequently lack the opportunity to cook their own meals (Durán-Agüero et al., 2023). However, food preferences and dietary choices play an essential role in promoting physical and mental health (Mikkawi, Khoury & Rizk, 2024). From the early years of life, proteins, polyunsaturated fatty acids (arachidonic acid, docosahexaenoic acid, eicosapentaenoic acid, and gamma-linolenic acid), B vitamins (such as B₁, B₆, and B₁₂), and minerals (e.g., selenium, zinc, magnesium, iron, copper, and iodine) play crucial roles in the development and healthy functioning of the nervous system (Wendołowicz, Stefańska & Ostrowska, 2018). The Mediterranean diet is abundant in grains, fruits, vegetables, legumes, nuts, oilseeds, and olives; high to moderate in fish and seafood; moderate in eggs, poultry, and dairy; low in red meat; and is composed of nutritional elements advantageous for the nervous system (Bach-Faig et al., 2011). Adherence to high-quality diets like the Mediterranean diet correlated with reduced depression, anxiety, and stress-related mental quality of life in a cross-sectional study of female adults (Açik, Altan & Çakiroğlu, 2022). In parallel, western diets high in fats and processed foods adversely impact mental health (Aslan Çin et al., 2022). Like a vicious circle, adverse emotional states promote high-fat and sugary food intakes (Fong et al., 2019). The dietary inflammatory burden was observed to be elevated in female university students with moderate to severe depression (Açik & Çakiroğlu, 2019).

The NOVA categorization system categorizes foods according to their level of natural content and the extent of industrial processing they undergo. It categorizes foods into four classifications: unprocessed and minimally processed foods (UPMP), processed culinary ingredients (PCI), processed foods (PF), and ultra-processed foods (UPF) (Monteiro et al., 2019). UPMP includes raw or minimally processed fresh fruits, vegetables, and meats. PCI includes oils, sugars, and salts used in culinary practices. PF includes foods that are processed, including canned vegetables or fruits with added salt or sugar. Lastly, UPF is characterized as “industrial preparations that are ready-to-eat or ready-to-heat, primarily composed of substances derived from food, frequently chemically altered, containing additives, and comprising a minimal amount of whole food” (Monteiro et al., 2019; Vitale et al., 2024). UPFs possess high levels of fat, salt, or sugar and are typically deficient in dietary fiber, protein, micronutrients, and beneficial functional substances (Monteiro et al., 2019). It has attracted attention due to its relation with multiple health effects (Pagliai et al., 2021; Juul et al., 2022).

Quality of life has been defined as “an overall general well-being that comprises objective descriptors and subjective evaluations of physical, material, social, and emotional well-being together with the extent of personal development and purposeful activity, all weighted by a personal set of values” (Karimi & Brazier, 2016). Recent studies indicate that the intake of UPFs significantly increases the risk of chronic diseases, including obesity, hypertension, cardiovascular diseases, type 2 diabetes mellitus, and cancer (Pagliai et al., 2021; Juul et al., 2022; Delpino et al., 2022). Furthermore, individuals who consume a substantial proportion of UPFs (51.1% of energy compared to 12.4% of energy) exhibit a deterioration in health related quality of life (HRQoL) (Cadenhead et al., 2023).

Mental distress is defined as “a significant disturbance in emotional processes, thoughts, or cognitions that impairs judgment, behavior, or the ability to cope with the ordinary demands of life” (Mutinta, 2022). A longitudinal study (Gómez-Donoso et al., 2020) of young adults possessing a college degree indicated that increased consumption of UPFs was associated with an elevated risk of depression. A similar finding was observed in a cohort study involving adults and the elderly (Adjibade et al., 2019). The consumption of UMPF correlates with reduced levels of depression. In contrast, the consumption of UPFs elevates the risk of anxiety (Coletro et al., 2022). A meta-analysis of 17 non-interventional observational studies indicated that the consumption of UPF was correlated with anxiety and depression (Lane et al., 2022a). A longitudinal study indicates that elevated consumption of UPFs correlates with depression in healthy adults (Ferreira et al., 2024).

Although the associations between UPF consumption and HRQoL or mood have primarily been shown in adults and the elderly, there is limited research examining this relationship among university students. This study aimed to assess the correlations between UPF intake, HRQoL, and mood among university students. Moreover, our aim was to set a potential cut-off above which UPF intake diminishes quality of life and exacerbates mental distress.

Material and method

Results

General information about the participants is given in Table 1. This study reached 595 individuals, 195 men (32.8%) and 400 women (67.2%), with a mean age of 21.2 ± 1.45 years.

Figure 1 shows the correlation results between the NOVA food group consumptions (energy %) and PCS12, MCS12 and MDS. We observe some relevant associations between PCS12, MCS12, MDS and UMPF, PCI, PF, and UPF. UPF were negatively associated with UPMP (r = −0.745, p < 0.001), PCI (r = −0.414, p < 0.001), PF (r = −0.524, p < 0.001), PCS12 (r = −0.211, p < 0.001) and MCS12 (r = −0.093, p = 0.024) while UPF were positively associated with MDS (r = 0.179, p < 0.001). UPMP were positively associated with PCS12 (r = 0.179, p < 0.001) and MCS12 (r = 0.083, p = 0.043). MDS was negatively associated with MCS12 (r = −0.608, p < 0.001). PF was not associated with any variables.

A linear regression analysis was conducted for both unadjusted and adjusted models for each dependent variable (PCS12, MCS12, and MDS). The stepwise procedure eliminated the other independent variables (UMPF, PCI, PF), and in the final model, only UPF is statistically significant. In Table 2, the results showed a substantial impact of UPF on PCS12, MCS12, and MDS in unadjusted model. However, UPF does not have a significant effect on MCS12 after adjusting the models. After adjustment for age, sex, physical activity, smoking duration, number of cigarettes and chronic disease, UPF was negatively associated with PCS12 (β = −0.112, p = 0.005) and positively related to MDS (β = 0.102, p = 0.002).

The results of the ROC analysis are presented in Table 3, and the corresponding ROC curves can be found in Fig. 2. Upon careful examination of the area under the curve values, it becomes evident that all of them significantly surpass the 0.5 threshold, providing sufficient evidence for substantial discrimination between the groups. The ROC analysis revealed statistically significant but modest discrimination ability for all three measures, with AUC values ranging from 0.574 to 0.642. While these values fall below the conventional threshold of 0.7 for good predictive performance, they indicate discrimination better than chance (Carrington et al., 2022). The optimal cut-off values for UPF consumption are 45.096% for the PCS12 group (high vs low physical quality of life), 50.999% for the MCS12 group (high vs low mental quality of life), and 40.250% for the MDS group (low vs moderate-to-high mental distress). In other words, it was found that those with UPF consumption above 45.096% had low physical quality of life, those above 50.999% had low mental quality of life and those above 40.250% had moderate-to-high mental distress in this study.

Discussion

Within this cross-sectional study of university students, we showed associations of UPF consumption with quality of life and mental distress. We established threshold values of UPF according to physical, mental quality of life components and mental distress.

One of the main results of this study was that both physical and mental quality of life components were negatively associated with UPF intake in correlation (Fig. 1) and unadjusted linear regression model (Table 2). After the adjustments of age, sex and physical activity the associations were still significant (Table 2). Health-related quality of life is based on an individual’s subjective evaluation of his own health and wellbeing and is a valuable outcome of healthcare (Vajdi & Farhangi, 2020). In a longitudinal study, there was a notable decrease in the quality of life ratings, partially ascribed to the rise in several adjustable risk factors (Olfson et al., 2018). There are a limited number of studies showing associations between UPF consumption and quality of life. Our findings relating to the UPF consumption and quality of life are reported for the first time with this study in Türkiye and are in agreement with recent limited literature. In a longitudinal study, unhealthy dietary habits such as UPF and sweet intakes were associated with lower health related quality of life in colorectal cancer survivors (Kenkhuis et al., 2023). In another study, Iranian adolescents with higher UPF consumption had poorer quality of life (Lane et al., 2022b). These findings are parallel with the results showed associations between “unhealthy” or “Western diet” and depressive symptoms (Vajdi & Farhangi, 2020) or adherence to an MD pattern is associated with better quality of life (Bonaccio et al., 2013).

We further determined a cut-off and found the UPF intake above 45.096% for physical component and 50.999% for the mental component of SF-12 was optimal to show the decreasing quality of life of each representative component (Fig. 2, Table 2). Zhang & Giovannucci (2023) reported that younger individuals tended to consume more UPFs. Moreover, elevated UPF consumption correlated with younger age, urban residency, and being single, such as unmarried, separated or divorced. Education, income, and social status had differing correlations according to the country (Dicken, Qamar & Batterham, 2023). The consumption of UPFs is linked to various health outcomes, including heightened risk of all-cause mortality, and noncommunicable diseases such as cardiovascular diseases, cerebrovascular diseases, hypertension, metabolic syndrome, obesity, depression, irritable bowel syndrome, cancers, gestational obesity, asthma and wheezing, and frailty, as indicated by cohort and cross-sectional studies (Chen et al., 2020). In a meta-analysis, increased UPF consumption was associated with a worse cardiometabolic risk profile and a higher risk of cardiovascular disease, cerebrovascular disease, depression and all-cause mortality (Pagliai et al., 2021). Similarly, Juul et al. (2022) concluded that a greater overall consumption of UPFs correlates with an elevated risk of type 2 diabetes, obesity, and cardiovascular disease in adulthood. UPF consumption is related to diabetes risk in a dose-dependent manner (Delpino et al., 2022) and higher consumption of UPF was strongly associated with a higher risk of multiple indicators of obesity in the adult population over a 13-year follow up (Rauber et al., 2021). These findings indicate that the percentage of energy from UPF consumption, which we have determined in our study, should be reduced. By reducing UPF consumption, the quality of life can be improved through disease prevention.

In this study, we demonstrated a positive association between UPF intake and mental distress (Fig. 1) and the associations were still significant after the adjusting for possible confounders (Table 2). Although the associations between diet and mental health are complex, diet can have direct effects on mood (Bremner et al., 2020). Previous investigations based on dietary components or patterns were previously related to mental health. They showed that diet has a fundamental role by being essential for the brain, having a role in the regulation of circadian rhythm, and the gut-brain axis, and contributing to inflammation and oxidative stress (Godos et al., 2020). Adopting healthy eating habits was linked to reduced mental distress and increased psychological well-being (Hong & Peltzer, 2017) whereas a growing body of evidence showed that high fast-food consumption (Begdache et al., 2020) and abnormal calorie intake (Cheon et al., 2020) were related to mental distress. In a nationally representative sample of American adults, those who reported consuming larger amounts of UPFs were more prone to experiencing mild depression, having more days with mental illness and anxiety, and less likely to report having no mentally unhealthy or anxious days (Hecht et al., 2022). In another study which included 1,693 adults from Brazil, the presence of a combination of two or three health risk behaviours, such as consuming high amounts of UPFs and not consuming fruits and vegetables on a daily basis, resulted in a greater occurrence of symptoms associated with anxiety or depression (Coletro et al., 2022). Similarly, Lane et al. (2022a) reported that greater UPF consumption was cross-sectionally associated with increased odds of depressive and anxiety symptoms. In the NutriNet-Santé cohort which included 20,380 women and 6,350 men aged 18–86 years, UPF consumption was positively associated with the risk of incident depressive symptoms after follow-up of 5.4 years (Adjibade et al., 2019). A positive association between UPF consumption and likelihood of having depressive symptoms was found in younger southern Italian adults (Godos et al., 2023). Our results support the previous findings.

When we performed a ROC analysis, an energy intake above 40.250% from UPF was significantly associated with increased moderate to high mental distress among the participants (Fig. 2, Table 3). A limited number of studies have indicated the amount or energy ratio of UPF consumption in terms of mental distress. In the SUN project which included 14,907 Spanish university graduates and followed up for a median of 10.3 years, a total of 774 incident cases of depression were identified and a higher risk of developing depression was found in the highest UPF consumption quartile. However, in this study UPF amounts were represented as g/day and reported that the 4^th quartile (192.7 g/day) was significantly different from the 1^st quartile (51.8 g/day) (Gómez-Donoso et al., 2020). In a recent meta-analysis UPF consumption is related to an enhanced depressive mental health status risk in a dose-dependent manner. Additionally, a 10% increase in UPF consumption per daily calorie intake increased the depression risk by 11% (Mazloomi et al., 2023).

There are several possible mechanisms for UPF consumption that potentially explain their effects on increased chronic disease risk (Crimarco, Landry & Gardner, 2022), mental health and eventually health-related quality of life. Diets high in UPFs generally reflect poor diet quality (Marchese et al., 2022; Moubarac et al., 2017; Shim et al., 2022; Vandevijvere et al., 2019; Houshialsadat et al., 2024). First mention of UPFs, by Monteiro et al. (2011) as “ultra-processed ready-to-eat or ready-to-heat food products” were shown to be consumed by both lower and upper-income groups and characterized by more added sugar, more saturated fat, more sodium, less fibre and much higher energy density. In a meta-analysis of nationally representative samples of various countries, UPFs were consistently associated with worsening diet quality (Martini et al., 2021). In a narrative review by Elizabeth et al. (2020), other possible mechanisms reviewed included a higher glycaemic load of the UPFs, diminished satiety signalling due to processing, harmful components formed during high-temperature cooking, and pro-inflammatory responses associated with industrial food additives, and imbalances in gut microbial community. Moreover, in recent years UPFs have been associated with food addiction (LaFata & Gearhardt, 2022). Young adults (18–35 years) with food addiction were shown to have higher energy % from UPFs and lower energy % from UPMP in an Australian study (Whatnall et al., 2022). Our research revealed that the consumption of UPFs accounted for 43.9% of the total energy intake among university students. Our findings align with the existing research, which has indicated a global increase in the intake of UPFs. Recent studies have indicated that such foods contribute to a substantial proportion, approximately 50–60%, of the total energy content in the typical diet of the average consumer in the United States, Canada, or the United Kingdom (Pagliai et al., 2021). Beyond these countries, data from Korea, Mexico, Brazil, and Sweden have the same increasing consumption trend (Zhang & Giovannucci, 2023). Although, the traditional Turkish dietary patterns are based on the Mediterranean diet, characterized by high consumption of legumes, vegetables, fruits, whole grains, and olive oil, and relatively low intake of processed foods (Pekcan, 2018), a transition in the dietary patterns especially in young groups was reported (Akman et al., 2010). In Türkiye, there are limited studies on UPF consumption. However, a recent study with 2,512 university students reported the UPF consumption ratio as 69.3% (Eroğlu, Ekici & Göktürk, 2025). Unfortunately, the large availability of UPFs on the market is supporting this trend (Şimşek et al., 2025).

As far as we know, this is the first study in Turkey that looks at the link between UPF and mental distress and quality of life using ROC-derived threshold values. This study makes a new contribution to the field by suggesting specific cut-off points for UPF intake based on mental and physical health quality. In most cases, previous studies looked at the general links between UPFs and psychological outcomes such as depression and anxiety (Mazloomi et al., 2023; Hecht et al., 2022; Coletro et al., 2022). Our results, on the other hand, give a more complete picture by looking at mental distress, quality of life, and population-specific intake thresholds. This makes it easier to use the information to improve public health, especially in university students in whom UPF consumption is rising (Pagliai et al., 2021; Zhang & Giovannucci, 2023).

There are several strengths and limitations in this study. Relatively large sample size and face-to face data collection are among the strengths. Furthermore, the FFQ was designed according to NOVA, and was much less time consuming. Our preliminary results showed consistent results among food groups of the food-mood questionnaire and the FFQ (Ertaş Öztürk & Uzdil, 2024). We controlled our results according to the potential confounders based on their theoretical relevance, empirical evidence from previous research. However, other potential confounders, such as socioeconomic status, academic stress, and sleep quality, that were not considered, may be included in further studies. Another limitation is that we could not show any causality because of the nature of the cross-sectional study design. Also, the cross-sectional study design may limit the generalizability of the results to nationwide. Lastly, our results showed very high mental distress among this young group that can be a limitation. The results of this study should be replicated by further longitudinal studies, and the cut-off values we showed in our study should be justified.

Conclusion

Our findings indicate that higher UPF consumption is associated with lower quality of life and higher mental distress. Intakes above 40% of energy from UPF may lead moderate to high mental distress, while 45% may decrease physical, and 51% may decrease the mental quality of life. These results have important implications for public health policies and university-based interventions as they demonstrate links between UPF and a lower quality of life, increased mental distress, as they suggest threshold values. Consequently, these results carry significant implications for public health, particularly for policymakers dealing with the food industry who should oppose the intake of UPFs and advocate for the consumption of minimally processed foods. There is a need for radical strategies to reduce the consumption of UPFs for the promotion of physical and mental quality of life and prevention of mental distress. From a public health perspective, these results indicate the necessity for dietary guidelines that recommend limits on UPF. Establishing nutrition education programs, limiting the availability of UPFs on campus, and making it simpler for students to obtain affordable, minimally processed food options should be encouraged. At the policy level, government and institutional parties should consider front-of-package labelling indicating the degree of processing. Implementing preventive nutritional changes is crucial for safeguarding these vulnerable populations. These changes toward nutrition, with targeted preventative interventions in academic settings, have the potential to greatly improve young adults’ physical and mental health.

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