The Impact of Ultra-Processed Food Consumption on Verbal Fluency and Learning: A Randomized Crossover Trial

Ultra-processed food consumption is a globally increasing trend (Pagliai et al., 2021) correlated with increased obesity, cardiovascular disease, diabetes, and all-cause mortality (Elizabeth et al., 2020). American college students consume twice as many calories from ultra-processed food, compared to minimally processed food (Juul et al., 2022), and ultra-processed food has a suggested impact on academic performance as well (Blum et al., 2022; Martin, 2022). Verbal learning and fluency tests measure cognitive processes that are foundational for academic achievement (Thomas, 2022; Whiteside et al., 2016). Framed in Maslow's theory of needs (1943), the focus of this study was to answer the question: "What is the causal impact of processing level of food consumed (ultra-processed vs. minimally processed) and postprandial time (30 minutes vs. 90 minutes) on verbal fluency and learning?" A quantitative, laboratory type controlled experiment was conducted with a 2x2 repeated-measures design. Two alternative breakfasts were designed to share essential ingredients and match total energy content but vary in processing level. Forty college students were randomized to receive each meal at the beginning or end of a one-week washout period. Two-way repeated-measures ANOVA revealed that verbal learning and phonemic fluency scores were highest at 30 minutes and 90 minutes, respectively. Regarding processing level, the ultra-processed meal improved phonemic fluency but not semantic fluency. However, the minimally processed meal improved four distinct measures of verbal learning. To enhance learning while simultaneously limiting chronic disease, it is recommended that institutions of learning and policymakers create environments that favor minimally processed food.