Longer-term mixed nut consumption improves brain vascular function and memory: A randomized, controlled crossover trial in older adults

Background: Nut consumption may reduce age-related cognitive decline, but underlying mechanisms are unclear. Objective: To investigate in older adults longer-term effects of mixed nut consumption on brain vascular function, which may underlie improvements in cognitive performance. Methods: Twenty-eight healthy individuals (age [mean & PLUSMN; SD]: 65 & PLUSMN; 3 years; BMI: 27.9 & PLUSMN; 2.3 kg/m2) were included in a randomized, single-blinded, cross-over trial with a 16-week intervention (60 g/d mixed nuts: walnuts, pistachio, cashew, and hazelnuts) and control period (no nuts), separated by 8 weeks of washout. Participants followed the Dutch food-based dietary guidelines. At the end of each period, ce-rebral blood flow (CBF), a marker of brain vascular function, was quantified using arterial spin labeling magnetic resonance imaging. Effects on endothelial function, arterial stiffness, and the retinal micro-vasculature were also assessed. Cognitive performance was measured using the Cambridge Neuropsy-chological Test Automated Battery. Results: Body weight remained stable during the study. As compared to the control period, the mixed nut intervention resulted in a higher regional CBF in the right frontal and parietal lobes (treatment effect: 5.0 & PLUSMN; 6.5 mL/100 g/min; P < 0.001), left frontal lobe (5.4 & PLUSMN; 7.1 mL/100 g/min; P < 0.001), and bilateral prefrontal cortex (5.6 & PLUSMN; 6.6 mL/100 g/min; P < 0.001). Carotid artery reactivity (0.7 PP; 95%CI: 0.2 to 1.2; P = 0.007), brachial flow-mediated vasodilation (1.6 PP; 95%CI: 1.0 to 2.2; P < 0.001) and retinal arteriolar calibers were higher (2 mm; 95%CI: 0 to 3; P = 0.037), and carotid-to-femoral pulse wave velocity lower (-0.6 m/s; 95%CI:-1.1 to-0.1; P = 0.032). Further, visuospatial memory (-4 errors [16%]; 95%CI:-8 to 0; P = 0.045) and verbal memory (+1 correct [16%]; 0 to 2; P = 0.035) improved, but executive function and psychomotor speed did not change. Conclusions: Longer-term mixed nut consumption as part of a healthy diet beneficially affected brain vascular function, which may relate to the observed beneficial effects on memory in older adults. Moreover, different characteristics of the peripheral vascular tree also improved. & COPY; 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).