Short answer. In a rigorous double-blind, randomized, placebo-controlled clinical trial (Wightman et al., Nutrients 2018;10(8):955), 140 healthy adults aged 50–70 consumed either 475 mg or 950 mg of standardized Sideritis scardica extract daily for 28 days. The 950 mg dosage produced statistically significant improvements in cognitive processing accuracy during Rapid Visual Information Processing (RVIP) tests and reduced state anxiety under acute mental challenge, corroborated by near-infrared spectroscopy measuring prefrontal cerebral blood flow.

Trial Design, Participant Demographics, and Dosing

Conducted at the Brain, Performance and Nutrition Research Centre (Northumbria University), the study recruited 140 healthy men and women aged 50 to 70 years. Participants were randomized into active treatment groups (475 mg Sideritis, 950 mg Sideritis, active comparator Ginkgo biloba 240 mg) or a matching placebo.

Cognitive assessments were administered at baseline (Day 1 acute) and following 28 days of continuous daily supplementation.

Quantified Cognitive and Hemodynamic Results

Following 28 days of 950 mg Sideritis scardica intake, participants demonstrated significantly faster and more accurate target detection on computerized Rapid Visual Information Processing tasks (p = 0.017) relative to placebo.

Near-infrared spectroscopy (NIRS) tracked real-time oxygenated hemoglobin levels in the prefrontal cortex, showing significant acute increases in localized cerebral perfusion during demanding cognitive tasks.

State anxiety scores assessed via the State-Trait Anxiety Inventory (STAI) showed a substantial reduction (Cohen's d = 0.75) under acute laboratory stress conditions.

Clinical Extract vs Artisanal Whole-Stem Brewing

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  • Study Reference: Wightman et al., *Nutrients* 2018;10(8):955 (PMID: 30042362).
  • Sample: 140 healthy adults aged 50–70 in a 28-day double-blind randomized trial.
  • Key Findings: Improved RVIP cognitive accuracy (p=0.017) and decreased state anxiety (d=0.75).
  • Mechanism: Prefrontal cerebral blood flow modulation measured via near-infrared spectroscopy.