Impact of anthocyanin-rich black rice consumption on cognitive function, inflammation and microvascular function in older adults: a crossover intervention trial

Abstract

Typical and atypical declines in cognitive function, as well as increases in chronic, low-grade inflammation and impaired vascular function are all impacted by the ageing process. Flavonoid-rich foods/beverages have been extensively shown to impact human cognition and to modulate immune and/or vascular function, although the cause-and-effect relationship between these factors is unclear. Here, we examine the acute (2 hours) and short-term (8 days) effects of anthocyanin-rich black rice on cognition, inflammation, and vascular function in older adults. Twenty-four older adults (65 ± 7 years) participated in a randomized, single-blind, crossover trial with one-week washout periods. Participants consumed either 210 g of anthocyanin-rich black rice (208 mg of anthocyanins) or the brown rice control (0 mg of anthocyanins) daily for 9 days. Acute effects were assessed 2 hours after consumption on days 1 and 9, and short-term effects were evaluated after completing 8 days of intake. Cognitive performance (RAVLT, digit span, Stroop, and digit symbol substitution), microvascular blood flow, and blood pressure were measured for both acute and short-term interventions, while serum inflammatory biomarkers were assessed for the short-term intervention. Anthocyanins and phenolic acids in rice were identified by using liquid chromatography-mass spectrometry (LC-MS). Data were analyzed using linear mixed models with Bonferroni-corrected comparisons. Eight days of black rice intake significantly improved verbal memory (RAVLT final recall: 12.64 vs. 11.92, p = 0.04; total recall: 52.57 vs. 49.54, p = 0.02) and enhanced digit span backward (change from baseline (CFB) = 0.83, p = 0.03) compared with brown rice. In parallel, black rice significantly reduced interleukin-6 (IL-6) levels (CFB: −0.67, p = 0.03), an effect not seen with the control. Acute black rice consumption attenuated declines in delayed recall (CFB: −1.17, p = 0.09) and recognition (CFB: −0.67, p = 0.19), while significant reductions were observed following brown rice intake. No significant treatment effects were observed for microvascular blood flow or blood pressure. Consumption of anthocyanin-rich black rice for 8 days improved verbal memory and reduced blood IL-6 in older adults. These data suggest for the first time that cognitive benefits induced by anthocyanin-rich black rice may be mediated by anti-inflammatory mechanisms. The clinical trial registry number is NCT06583785 (https://clinicaltrials.gov).