Effects of Heat-Treated Green Tea Extract on Memory Function and Default Mode Network Connectivity in Individuals with Subjective Memory Impairment: A Randomized, Double-Blinded, Placebo-Controlled Trial

Given the increasing interest in the potential cognitive benefits of green tea, this study evaluated the efficacy of processed green tea products as nootropic agents. We conducted a 12-week, randomized, double-blinded, placebo-controlled trial to assess the effects of heat-treated green tea extract (HT-GTE) supplementation on memory performance in individuals with subjective memory impairment (SMI). A total of 80 participants with SMI (mean age 49.6 ± 5.6 years) were randomly assigned to either the HT-GTE group (n = 40) or the placebo group (n = 40). Memory performance was assessed using standardized composite scores at baseline and week 12. Additionally, we examined changes in functional connectivity (FC) within the default mode network (DMN), a key resting-state network associated with memory function, at both time points. Compared to the placebo group, the HT-GTE group demonstrated significant improvements in memory function after 12 weeks, as evidenced by a greater increase in composite scores (z = 2.535, P for interaction = .011). Furthermore, the HT-GTE group exhibited increased FC within the right precuneus region of the DMN (z = 2.554, P for interaction = .011). These findings underscore the potential of HT-GTE supplementation to enhance memory performance and FC within the DMN in middle-aged individuals with SMI, offering valuable insights into the cognitive benefits of green tea.