Effect of Creatine Monohydrate Supplementation on Macro- and Microvascular Endothelial Function in Older Adults: A Pilot Study

<b>Background/Objectives:</b> A pilot study was conducted to investigate the effect of four weeks of creatine monohydrate (CrM) on vascular endothelial function in older adults. <b>Methods:</b> In a double-blind, randomized crossover trial, twelve sedentary, healthy older adults were allocated to either the CrM or placebo (PL) group for four weeks, at a dose of 4 × 5 g/day for 5 days, followed by 1 × 5 g/day for 23 days. Macrovascular function (flow-mediated dilation [FMD%], normalized FMD%, brachial-ankle pulse wave velocity [baPWV], pulse wave analysis [PWA]), microvascular function (microvascular reperfusion rate [% StO₂/sec]), and biomarkers of vascular function (tetrahydrobiopterin [BH₄], malondialdehyde [MDA], oxidized low-density lipoprotein [oxLDL], glucose, lipids) were assessed pre- and post-supplementation with a four-week washout period. <b>Results:</b> CrM significantly increased FMD% (pre-CrM, 7.68 ± 2.25%; post-CrM, 8.9 ± 1.99%; <i>p</i> < 0.005), and normalized FMD% (pre-CrM, 2.57 × 10^-4 ± 1.03 × 10^-4%/AUC_SR; post-CrM, 3.42 × 10^-4 ± 1.69 × 10^-4%/AUC_SR; <i>p</i> < 0.05), compared to PL. Microvascular reperfusion rates increased following CrM (pre-CrM, 2.29 ± 1.42%/sec; post-CrM, 3.71 ± 1.44%/sec; <i>p</i> < 0.05), with no change following PL. A significant reduction in fasting glucose (pre-CrM, 103.64 ± 6.28; post-CrM, 99 ± 4.9 mg/dL; <i>p</i> < 0.05) and triglycerides (pre-CrM, 99.82 ± 35.35; post-CrM, 83.82 ± 37.65 mg/dL; <i>p</i> < 0.05) was observed following CrM. No significant differences were observed for any other outcome. <b>Conclusions:</b> These pilot data indicate that four weeks of CrM supplementation resulted in favorable effects on several indices of vascular function in older adults.