Ultra-processed food exposure and cognitive outcomes: a systematic review of observational studies

Ultra-processed food (UPF) intake has been associated with negative health outcomes. Research investigating UPF intake and cognitive health outcomes has begun. The aim of this review is to summarise the existing evidence of associations between exposure to UPFs, as defined by the NOVA food classification system, and cognitive health outcomes. We conducted a systematic search across multiple databases for relevant studies up to October 2024. The Newcastle-Ottawa Scale was used to assess the quality of included studies. A narrative approach was used to summarise and integrate results across studies. 383 articles were screened and five met the inclusion criteria. The association between UPF intake and four different cognitive outcomes (dementia risk, cognitive impairment risk, cognitive performance and cognitive change trajectories) was explored. Three out of the five studies found a significant negative main effect of consuming UPF on the outcome of interest. All studies identified adverse associations of consumption; for some studies, these negative associations were isolated to a subgroup of the population or a subgroup of UPF type. Conclusions should be drawn with caution due to the limited number of studies available examining UPF intake according to NOVA and its association with cognitive outcomes, as well as the variability in cognitive measures assessed. Due to the novelty of this research area, more studies are required to help elucidate whether, and how, UPF may affect cognitive health. Additionally, future analyses should incorporate a measure of overall diet quality to aid in determining whether the effect of UPF is independent of dietary pattern or influenced by it. PROSPERO registration number CRD42024600338.