Enhanced memory function and reduced perceived stress in older adults with self-reported memory complaints following strawberry leaf extract supplementation: a randomized, double-blind, placebo-controlled study

BACKGROUND: Age-related changes in cognitive performance represent a growing concern for older adults. Strawberry leaf extract (SLE), a polyphenol-rich botanical supplement containing ellagitannins, has been suggested to exert neuroprotective effects based on preclinical evidence. However, to date, no human studies have evaluated its potential benefits on cognitive performance. OBJECTIVES: The present study aimed to evaluate the impact of SLE supplementation on cognitive performance (i.e., memory abilities and executive functions) and mental well-being (stress level, sleep quality and fatigue) in healthy older adults with subjective memory complaints. METHODS: In this randomized, double-blind, placebo-controlled trial, 109 participants aged 60-80 years were randomly assigned to receive either SLE (300 mg/day) or a matching placebo for 12 weeks. Cognitive performance was assessed at baseline, midpoint, and endpoint using Cambridge Neuropsychological Test Automated Battery (CANTAB) subtests targeting memory abilities and executive functioning. Self-perceived stress level, sleep quality, fatigue, and memory complaints were evaluated using validated questionnaires. RESULTS: No significant treatment-by-time interactions were observed for the primary or secondary outcomes in the mixed-effects models. Exploratory analyses showed significant within-group improvements in episodic memory in the SLE group, with reductions in PAL total errors at Week 6 (-4.2 ± 10.0; p = 0.001) and Week 12 (-5.5 ± 11.2; p = 0.001). Between-group comparisons of change from baseline showed greater improvements with SLE than placebo for PAL total errors at Week 6 (p = 0.016) and Week 12 (p = 0.048), and for perceived stress at Week 6 (p = 0.043). The product was well tolerated, with no serious adverse events reported. CONCLUSIONS: Although the primary analysis did not demonstrate significant treatment-by-time interactions, exploratory analysis suggested that SLE may have beneficial effect on episodic memory and self-perceived stress level in healthy older adults with self-reported memory complaints. Further studies are warranted to confirm these effects.