A pilot randomized controlled trial of the effects of dietary nitrate supplementation on dynamic cerebral autoregulation in older adults with metabolic syndrome.

Metabolic syndrome (MetS) is associated with reduced nitric oxide (NO) bioavailability and impaired cerebrovascular function, potentially increasing cognitive decline risk. Dynamic cerebral autoregulation (dCA) maintains cerebral blood flow and may involve NO-related vascular mechanisms. Whether dietary nitrate supplementation influences dCA in MetS remains unclear. This pilot trial evaluated feasibility and explored effects of nitrate supplementation on dCA. Twenty-two older adults with MetS (55-75 years) were randomized in a double-blind, placebo-controlled design to receive nitrate-rich beetroot juice (BRJ; 6.4 mmol NO3 -·day-1) or nitrate-depleted placebo for 4 week. dCA was assessed using transfer function analysis (TFA) of beat-to-beat blood pressure and functional near-infrared spectroscopy-derived cerebral oxygenation. Primary analyses examined frontal dCA holistically, with exploratory regional and cognitive outcomes. dCA was indexed by TFA phase and gain. The intervention was well tolerated, adherence was high, and BRJ increased plasma nitrate concentrations versus placebo (p < 0.001). No significant effects were observed for frontal dCA or cognition. Exploratory analyses indicated region-specific differences in dCA in select frontal areas, characterized by improvements in TFA phase and gain. This pilot trial demonstrates the feasibility of dietary nitrate supplementation in MetS. While no effects were observed in primary outcomes, exploratory analyses suggest potential region-specific improvements in dCA.