Investigating the Relationship Between Ultra-Processed Food Consumption and Academic Performance in the Adolescent Population: The EHDLA Study

Adolescence is marked by substantial changes in physical, mental, and social aspects that shape how individuals interact, make choices, think, and experience emotions [1]. Notably, adolescence represents a crucial period for brain development that is characterized by the refinement of synapses, the formation of myelin sheaths, and the establishment of neural connections, particularly in the prefrontal cortex [2,3]. This neurological growth is accompanied by the gradual acquisition of progressively refined cognitive abilities which have a reciprocal relationship with academic performance [4].

The importance of academic performance for adolescents cannot be overstated, as it significantly impacts their growth and future opportunities. For example, one’s academic achievements could influence their educational trajectory and career prospects [5]. Moreover, involvement in educational activities, exploring various disciplines, and expanding one’s knowledge base contribute to the development of analytical thinking, problem-solving capabilities, and cognitive abilities [5]. Successfully meeting academic targets promotes feelings of accomplishment, self-worth, and assurance [6], potentially leading to improved psychological well-being [7]. However, despite these advantages, numerous factors could affect academic performance, including external influences (such as socioeconomic background [8]), personal characteristics (like sedentary lifestyle [9], physical activity [9,10], sleep patterns [11], nutritional choices [12], and weight status [13]), and educational environment (for instance, the type of educational institution [14]).

In the realm of official reports and nutrition research, there is growing recognition that ultra-processed foods (UPFs) are detrimental to human health [15,16,17,18]. UPFs are defined as industrial formulations primarily composed of food-derived substances, additives, and synthetic ingredients [19]. These products are engineered to be convenient, shelf-stable, and highly palatable, but they often contain excessive amounts of salt, sugar, and fat, while offering minimal nutritional benefits, such as in the case of snack foods, sugar-sweetened drinks, ready-to-eat meals, or fast food [20]. The negative impact of UPFs on dietary quality and their association with increased health risks is becoming increasingly apparent [21,22]. From 1990 to 2010, unhealthy food consumption rose globally, with variations being observed across different regions and countries [23]. UPFs constitute a significant portion of diets worldwide, accounting for 20% to over 60% of total energy intake, based on the nation and age group [17]. Despite this prevalence, UPFs have not received adequate attention in public health initiatives [20]. To address this oversight, it is essential to establish a clear link between UPF consumption and cognitive outcomes through robust scientific evidence.

The previous literature has tested the link between diet quality and academic performance in the young population [12,24]. For instance, a systematic review by Burrows et al. [24] pointed out that consistent breakfast consumption, nutrient-poor foods, lower intake of energy-dense foods, and overall diet quality are moderately associated with higher academic performance in the young population. Furthermore, a systematic review and meta-analysis by López-Gil et al. [12] reported a significant association of adherence to the Mediterranean diet with academic performance among children and adolescents. Specifically, some studies have assessed the link between UPFs and cognitive outcomes in the young population [25,26] with contradictory findings. The study by Liu et al. [25] indicated that frequent consumption of individual UPFs (sweet bakery products, candies) and global UPF consumption were related to lower Verbal Comprehension Index scores (a marker of the cognitive function) in children aged 4–7 years from China. Conversely, another study by dos Santos et al. [26] found that no association was identified between UPF consumption and cognitive functioning in low-income adolescents from Brazil.

Although evidence highlights the connection between diet quality and both cognitive and educational outcomes, the specific association between UPF consumption and academic performance in adolescents remains unexplored. This research gap is particularly significant as adolescence represents a critical period for cognitive development and the formation of long-term dietary habits [3]. Understanding this relationship is increasingly urgent given the rising prevalence of UPF consumption and its potential consequences for both health and education [21,22]. In the Spanish context, where dietary patterns are shifting and academic challenges among adolescents are well documented, addressing this issue is especially pertinent [27,28,29]. Therefore, the present study aims to examine the association between UPF consumption and academic performance indicators, focusing on specific subjects such as language, maths, and English, as well as overall grade point averages, in a sample of Spanish adolescents. The findings are expected to contribute to the design of evidence-based interventions and policies that promote healthier eating habits and enhance educational outcomes within this vulnerable population.

Table 1 summarizes the characteristics of the study participants. The median weekly UPF consumption was 4.0 servings (IQR 2.9 to 6.0) and 240.4 g (IQR 157.5 to 385.4). The median GPA, language, maths, and foreign language (i.e., English) scores were 6.3 points (IQR 4.7 to 7.7), 7.0 points (IQR 5.0 to 8.0), 6.0 points (IQR 4.0 to 8.0), and 6.0 points (IQR 5.0 to 8.0), respectively. The internal consistency (α) of the UPF items from the FFQ yielded a value of 0.89, indicating high reliability and supporting the coherence of the selected items in measuring UPF consumption.

Figure 1 displays the adjusted marginal means for GPA, language, maths, and foreign language in relation to the rations of UPF consumed. After adjusting for covariates, significant dose–response associations were identified, with greater UPF consumption corresponding to lower GPA (unstandardized beta coefficient [B] = −0.58; 95% CI −0.86 to −0.31; p < 0.001), language (B = −0.56; 95% CI −0.86 to −0.26; p < 0.001); maths (B = −0.58; 95% CI −0.92 to −0.25; p < 0.001), and foreign language (B = −0.61; 95% CI −0.90 to −0.32; p < 0.001) scores. Furthermore, when analyzing UPF consumption by tertiles (low, medium, and high) in relation to academic performance indicators (GPA, language, maths, and English), a clear trend emerged, showing that higher UPF consumption corresponded to progressively lower performance in all domains (see Figure S1). Notably, significant differences were observed between the low- and high-consumption groups for GPA (p = 0.001), language (p = 0.001), maths (p = 0.011), and English (p = 0.003), with a consistent decline in scores being seen as UPF consumption increased. The full results of the GLMs are detailed in Tables S2–S5. An additional analysis examining the association of servings of different UPF groups consumed with academic performance (i.e., grade point average) can be found in Table S6. These analyses revealed that higher consumption of most of the UPF groups (i.e., fast food, dairy products, beverages, fried foods, and sweets) were significantly associated with lower academic performance (p < 0.05 for all), while no significant association was found for sausages.

Table 2 indicates the adjusted marginal means of GPA, language, maths, and foreign language according to the status of the UPFs consumed. Overall, after adjusting for covariates, significant associations were identified. The highest UPF tertile showed the lowest academic performance and the lowest UPF tertile reported the highest academic performance. Adolescents with low UPF consumption showed the highest scores across academic performance indicators, including GPA (6.6, 95% CI 6.4 to 6.9), language (7.0, 95% CI 6.7 to 7.3), maths (6.2, 95% CI 5.9 to 6.5), and English (6.6, 95% CI 6.4 to 6.9). Similarly, those with medium UPF consumption reported slightly lower scores in GPA (6.4, 95% CI 6.1 to 6.7), language (6.7, 95% CI 6.4 to 7.0), maths (6.0, 95% CI 5.7 to 6.4), and English (6.6, 95% CI 6.3 to 6.9). In contrast, adolescents with high UPF consumption displayed the lowest academic performance scores, including GPA (5.6, 95% CI 5.4 to 5.9), language (6.0, 95% CI 5.7 to 6.3), maths (5.2, 95% CI 4.9 to 5.6), and English (5.7, 95% CI 5.5 to 6.0). The differences between high UPF consumption and low or medium UPF consumption were significant for all indicators (p < 0.05).

The results of our study highlight that increased consumption of UPFs is associated with lower academic performance, including lower GPAs and reduced performance in language, maths, and English as a foreign language, among the adolescent population studied. These observations are in line with previous research that has demonstrated a relationship between UPF consumption and decreased cognitive function in young people [25,26]. Furthermore, our findings support the existing literature that has established a connection between improved diet quality and enhanced academic performance in youths [12,24]. Although the precise mechanisms through which UPF consumption might affect adolescents’ academic performance are not yet fully understood, several potential explanations could account for these observed relationships.

On the one hand, UPFs are habitually rich in saturated fats, added sugars, and artificial additives while being low in essential nutrients such as vitamins, minerals, and antioxidants [19]. This nutritional imbalance could negatively affect cognitive function and brain development, which are critical during adolescence. For instance, diets high in UPFs are often deficient in omega-3 fatty acids [19], a nutrient linked to improved learning abilities, enhanced cognitive functioning [40,41], and higher relational memory in young populations [42,43]. Moreover, research has demonstrated that supplementary sugars, especially high-fructose corn syrup, negatively impact hippocampal functioning during crucial developmental stages in adolescent rats [44] and American children [45]. In line with this finding, the consumption of a “Western diet” that is high in UPFs such as ice cream, fast food, and chocolate has been linked to decreased neurocognitive performance, particularly in memory processes that depend on hippocampal integrity [46,47,48]. This hypothesis is supported by evidence from both animal models and studies in children. However, caution is warranted when extrapolating findings from animal research to humans. While adolescence is a common developmental stage across mammals, the complexity of the human brain and adolescent behavior is unparalleled [49]. This complexity restricts the direct applicability of animal model findings to human adolescents despite shared neurophysiological features. Further longitudinal and experimental research in humans is needed to better understand these potential effects.

Second, UPFs are often high in sugar [50], leading to rapid fluctuations in blood glucose levels [51]. These variations may negatively affect cognitive performance by reducing alertness and increasing fatigue, thereby hindering the ability to maintain sustained focus on academic tasks [52,53]. In this sense, a comprehensive review and meta-analysis conducted by Mantantzis et al. [54], pointed out that the consumption of carbohydrates significantly reduces alertness within 60 min and increase fatigue within 30 min after ingestion. This short-term energy instability, when consistently experienced, may lead to habitual energy deficits and a reduced capacity to perform academically. While these findings highlight potential mechanisms linking UPF consumption to academic outcomes, further research is needed to confirm these effects in adolescents and explore potential long-term impacts on cognitive functioning.

Third, while our analyses accounted for sleep duration, frequent consumption of UPFs has been associated with poor sleep quality, including insomnia [55] and disrupted sleep patterns [56]. These effects may be attributed to the presence of stimulants, such as caffeine, commonly found in sugary beverages and snacks [57]. Sleep disturbances can significantly impair academic performance by limiting the brain’s capacity to consolidate newly learned information [58] and by reducing critical cognitive functions, including alertness, attention, decision-making, judgment, and overall cognitive efficiency [59]. These findings underscore the potential role of UPF consumption in disrupting sleep and indirectly affecting academic outcomes, warranting further investigation into this connection in adolescent populations.

Fourth, the high consumption of refined sugars and trans fats, commonly found in UPFs, could contribute to chronic low-grade inflammation [60,61]. This systemic inflammation has been linked to impairments in brain function, including reduced synaptic plasticity and memory deficits [62]. Furthermore, inflammation can compromise the integrity of the blood–brain barrier (BBB), a protective structure between the bloodstream and the brain [63]. When the BBB is weakened, inflammatory mediators increase its permeability, allowing immune cells and pro-inflammatory cytokines to infiltrate the brain [64]. This infiltration triggers neuroinflammation, which disrupts neuronal function and is associated with cognitive decline [62]. In adolescents, such disruptions could have significant implications for learning and academic performance. Cognitive functions critical for academic success, such as memory, attention, and problem solving [4], may be impaired, contributing to lower academic achievements in this population [26].

This study has notable limitations that must be acknowledged. First, its cross-sectional design prevents the establishment of causality. Further investigation is needed to determine whether decreasing UPF consumption results in superior academic performance. Furthermore, the relationship’s direction is uncertain, as higher academic performance might explain lower UPF consumption. To ascertain if increased UPF consumption directly leads to poorer academic results in adolescents, longitudinal investigations are necessary. Second, the reliance on self-reported data introduces potential social desirability and recall biases, possibly influencing the accuracy of the reported UPF consumption. Third, while the analysis considers various covariates, academic performance is affected by multiple factors and unaccounted variables could impact the observed outcomes. Fourth, the findings may not be fully applicable to other regions of Spain or different countries due to contextual and cultural variations in dietary habits. Lastly, while the biological mechanisms linking the consumption of UPFs with academic performance are likely universal, external factors such as access to healthy foods, cultural traditions like the practice of sharing family dinners, variations in UPF composition resulting from local regulations, and socioeconomic status can significantly influence the magnitude and direction of these effects. Despite these limitations, the study provides cross-sectional evidence on the association of UPF consumption with academic performance among adolescents, an understudied group. The inclusion of numerous covariates, including lifestyle, sociodemographic, and anthropometric variables, strengthens the consistency of the findings.

Our study identifies a negative association between UPF consumption and academic performance in adolescents, highlighting it as a modifiable factor that could impact academic outcomes. Adolescents with higher UPF consumption exhibited consistently lower grades across various academic indicators, emphasizing the importance of dietary quality during this critical developmental period. This finding highlights the need for a multifaceted approach to promote healthier eating habits that involves schools, families, and public health policies. Implementing strategies such as nutrition education programs tailored to adolescents, enhancing the nutritional standards of school meal offerings, and restricting the availability of UPFs in educational environments (e.g., through policies that limit the sale of UPFs in vending machines, cafeterias, and school events or by providing healthier, more appealing alternatives) could significantly contribute to improving academic outcomes. Furthermore, these interventions have the potential to mitigate disparities in educational attainment that are linked to diet quality. Given the long-term psychological, social, and economic implications of academic achievement, reducing UPF consumption among adolescents should be prioritized as part of broader public health efforts aimed at supporting youth development and success.