Acute effects of fresh versus dried Hayward green kiwifruit on sleep quality, mood, and sleep-related urinary metabolites in healthy young men with good and poor sleep quality.
Level 2 - randomized trial
Randomized, single-blind crossover trial in humans
PubMed 36998905 · doi:10.3389/fnut.2023.1079609
What was done
A randomized, single-blind crossover trial in 24 men (age 29 ± 1 years, BMI 24 ± 1 kg/m²; 12 good sleepers, 12 poor sleepers) tested the acute effects of three interventions consumed at home with a standardized evening meal: flesh of two fresh green kiwifruits, dried green kiwifruit powder (including skin) mixed with water, or a water control. Primary outcomes included subjective and objective sleep quality, mood, and waking urinary concentrations of 5-hydroxyindoleacetic acid (5-HIAA, a serotonin metabolite), 6-sulfatoxymelatonin (aMT6s), vitamin C, and B-vitamins.
What was found
Both fresh (+1.56 ± 0.4 ng/g, p = 0.001) and dried (+1.30 ± 0.4 ng/g, p = 0.004) kiwifruit significantly elevated urinary 5-HIAA concentration above control (4.32 ± 0.4 ng/g). Dried kiwifruit consumption improved morning sleepiness, waking alertness, and vigor across all participants (p < 0.05). In poor sleepers, ease of awakening improved by 24% with dried kiwifruit (p = 0.005) and showed a trend toward improvement with fresh kiwifruit (+13%, p = 0.052). In good sleepers, getting-to-sleep ratings trended upward with fresh kiwifruit (+9%, p = 0.053). Both forms showed non-significant trends toward improved esteem and total mood disturbance (p < 0.1). Objective sleep outcomes and melatonin metabolite levels were not quantitatively detailed in the abstract.
Why it matters
This study provides initial evidence that acute evening kiwifruit consumption increases peripheral serotonin metabolite excretion while modestly enhancing subjective morning wakefulness and ease of rising.
Limits
The study was very small (n = 24) and limited strictly to young men, precluding generalization to women or older adults. Interventions were tested acutely rather than over sustained periods, and the comparator was plain water rather than a blinded, macronutrient-matched placebo control.
Cited by
- partial Studies show that kiwifruit and its constituent phytochemicals such as apigenin reduce cognitive function and arousal to promote sleep.