Systematic review and meta-analysis of isoflavone interventions on cognitive function

Isoflavones (ISFs) are plant-derived compounds, found mainly in legumes and most abundantly soy, with oestrogenic properties. These ISFs have been investigated for their potential to influence cognitive function, particularly in aging populations. Our review aimed to assess the overall landscape of dietary soy or isoflavone intervention effect on cognitive functions and to determine the statistical significance of their effects on specific cognitive domains. A systematic literature search was conducted across major databases (PubMed, Scopus, Web of Science) to identify relevant studies (n = 37). The RCTs were then subjected to a meta-analysis where data was available (n = 16). In terms of risk of bias and methodological quality, the vast majority (n = 27) scored positively with the remainder receiving neutral ratings (n = 9). The meta-analysis pooled effect size for composite cognitive function was significant, 0.25 [0.04, 0.45], whilst domain-specific meta-analyses revealed a significant positive effect on memory, with a pooled effect size of 0.33 [0.04, 0.62]. The effects on executive function, psychomotor speed and processing speed were not significant. The findings in the systematic review consisted of two studies showing negative significance, fifteen studies showed positive significant outcomes, seven showing bidirectional significant outcomes and the remaining thirteen studies showing no significance. The meta-analytic portion provides statistical evidence that isoflavone supplementation can significantly influence specific domains of cognitive function, particularly memory. While the overall composite effect was modest, the domain-specific findings suggest that isoflavones may be a beneficial dietary intervention for targeted cognitive improvements, namely memory outcomes.