Benefits of Dietary Supplementation with Specific Silicon-Enriched Spirulina on Arterial Function in Healthy Elderly Individuals: A Randomized, Placebo-Controlled Trial

<i>Background/Objectives</i>: Vascular aging is associated with increased arterial stiffness and changes in the wall structure, leading to a loss of elasticity. Silicon is abundant in arteries and plays a key role in the synthesis and stabilization of elastin fibers. In animal models of accelerated cardiovascular aging, a specific nutritional supplement based on silicon-enriched spirulina (SpSi) has been shown to have beneficial effects on vascular function. The present study, designed as a randomized, double-blind, placebo-controlled trial, aimed to evaluate the effectiveness of this SpSi supplement on aging-related changes in vascular function among healthy older adults. <i>Methods</i>: Here, 120 healthy volunteers aged 60-75 years were enrolled and randomly assigned to either the SpSi group (<i>n</i> = 60) or placebo group (<i>n</i> = 60). Over 6 months, the participants received either 3.5 g of specific 1% silicon-enriched spirulina (SpSi group) or placebo tablets daily. The primary outcome was the assessment of arterial wall pressure waveforms, which included blood pressure (BP) readings and the determination of the aortic pulse wave velocity (aPWV). Secondary outcomes included the vasomotor endothelial function through post-ischemic vasorelaxation, measured using the reactive hyperemia index (RHI), and carotid intima-media thickness. <i>Results</i>: When considering the entire sample, none of the studied parameters differed between the placebo and SpSi groups. However, when focusing on individuals with high-normal blood pressure (i.e., systolic BP between 130 and 150 mmHg) and aPWV levels above cutoff values (>10 m/s), the BP decreased by 8% (<i>p</i> < 0.001) and aPWV decreased by 13.5% (<i>p</i> < 0.0001) in subjects receiving SpSi. In individuals with BP and aPWV levels below the cutoff values, no effect was observed. <i>Conclusions</i>: In healthy elderly individuals, SpSi supplementation improved high-normal blood pressure and aortic pulse wave velocity, suggesting an enhanced vascular function.