Sleep supplements

Sleep supplements are non-prescription products, including hormones, minerals, amino acids and plant extracts, that are taken with the aim of improving sleep. This section covers eight: Melatonin, Magnesium, Glycine, L-theanine, Ashwagandha, GABA, Apigenin and Valerian. They act through different parts of the sleep system described in sleep regulation: melatonin through the timing of the circadian clock (the roughly 24-hour internal body clock), glycine through the drop in core body temperature at the start of sleep, magnesium, apigenin, valerian and GABA through the brain's main inhibitory (calming) signalling system, GABA, or related receptors (docking sites on nerve cells), and L-theanine and ashwagandha through the stress response that is raised in insomnia.

Most of these products are sold without prescription as dietary or food supplements [1, 2]. Their measured content can differ from the label: in an analysis of 31 melatonin supplements, melatonin content ranged from 83% below to 478% above the labelled amount, more than 71% of products fell outside 10% of the label claim, and 8 contained serotonin (a chemical messenger in the brain and gut) [1]. A Cochrane review (an independent review that pools trial results) of melatonin for jet lag called for routine pharmaceutical quality control of melatonin products [3]. The 2017 American Academy of Sleep Medicine guideline, which reviewed hypnotics (sleeping medicines) approved by the US Food and Drug Administration alongside agents used for insomnia without that approval, suggested that clinicians not use melatonin or valerian for chronic insomnia in adults (weak recommendations) [4].

The measured effects are generally small. In primary sleep disorders (those not caused by another condition), melatonin shortened the time to fall asleep by about 7 minutes across 19 trials with 1,683 participants [5], while in jet lag 9 of 10 trials found a benefit [3]. Pooled trials of magnesium in 151 older adults found sleep onset 17.36 minutes faster, from trials at moderate to high risk of bias (design flaws that can skew results) [6]. Ashwagandha showed a small but statistically significant (unlikely to be due to chance) effect on overall sleep across 5 trials with 400 participants [7]. For valerian, 16 trials with 1,093 patients were mostly of poor methodological quality, with evidence of publication bias (positive results being published more often than negative ones) [8], and a review of 14 trials of oral GABA found very limited evidence for sleep [9].

The list is ordered by how directly each compound's mechanism bears on sleep and by the maturity of the human evidence, with meta-analyses (studies that pool the results of earlier trials) of randomised trials (in which participants are assigned to groups by chance) ranked above single small trials and those above laboratory and animal studies. The order is not a ranking of effects on lifespan, and no longevity effect is estimated for any supplement. The pages are educational and describe doses as they were used in studies, not as recommendations.