*3.5. Other Interventions*

The combination of γ-aminobutyric acid (GABA; an amino acid produced by natural fermentation) and *Apocynum venetum* leaf extract treatment yielded a modest decrease in SOL of 4.3 min and shortening of deep non-REM sleep latency by 5.3 min [33]. Similar magnitude reductions in SOL were reported for 100 mg of GABA supplementation only [39], while supplementation with 300 mg of GABA induced reductions in SOL and WASO in concert with an increase in SE [34]. In comparison, the consumption of two kiwifruits 1 h

before bedtime yielded a substantial increase in TST of 55 min, as well as a 2% increase in SE and decreased SOL (14 min) and WASO (6.1 min) [32]. In athletes, beetroot juice showed an improvement in subjective quality of sleep as measured by the PSQI [23]. In healthy adults, 3 g of glycine ingested an hour before bed decreased SOL and the onset latency of slow wave sleep [37]. Similarly, 3 g of glycine led to decreases in morning fatigue when ingested an hour before bed [36], and an improvement in cognitive function during periods of sleep restriction when ingested 30 min before bed [29]. In adults who were dissatisfied with sleep, 3 g of L-serine ingested 30 min before bed improved subjective sleep quality and sleep satisfaction; however, in a smaller sub-study, there were no improvements in actigraphy-measured sleep [38]. Finally, consuming a tart cherry-based sleep supplement powder reduced SOL (10 min) in poor sleeping young adults [35].
