Effects of dietary fermented blueberry leaf tea on sleep: a randomized double-blind controlled trial

This study investigated the effects of dietary fermented blueberry leaf tea on sleep quality through a 3-week double-blind randomized controlled trial. Fifty healthy individuals (BMI: 22.3 ± 0.6 kg m⁻²), aged 20–69 years, were randomly assigned to either an active group consuming the fermented blueberry leaf tea or a placebo group. They consumed 200 mL of active tea (1.8 mg hyperoside/serving) or placebo tea three times daily. Sleep quality was assessed using both objective and subjective measures via actigraphy and the Oguri–Shirakawa–Azumi Sleep Inventory MA (OSA-MA) version questionnaire, respectively. We observed significantly higher sleep efficiency (active: from 82.2 ± 1.4% to 81.2 ± 1.6%, placebo: from 83.8 ± 1.6% to 80.4 ± 1.8%) and lower wake after sleep onset (WASO) (active: from 68.9 ± 6.6 min to 70.5 ± 6.8 min, placebo: from 61.9 ± 6.9 min to 77.9 ± 8.6 min) in the active group compared to the placebo group. Specifically, the active group exhibited higher sleep efficiency after 3 weeks and reduced WASO after 2 weeks of active tea consumption. Subjective evaluations indicated significant improvements in sleep onset and maintenance as early as one week, correlating with the objective sleep efficiency measures. On the other hand, no significant differences were observed in other parameters of actigraphy or OSA-MA. These findings suggest that hyperoside, a quercetin glycoside found in blueberry leaves, may positively influence sleep quality by increasing serotonin and melatonin levels, thereby enhancing non-rapid eye movement sleep. Regular consumption of dietary fermented blueberry leaf tea may improve daily sleep quality, leading to a better overall quality of life.