Sleep and supplements: what the evidence says

Your body clock runs on regularity, and the most reliable way to sleep better is to keep a consistent wake time seven days a week, even after a bad night. A steady schedule strengthens the natural rise and fall of melatonin and body temperature that make you sleepy at the right time. No supplement on this page will out-perform simply going to bed and, crucially, waking up at roughly the same time every day.

Caffeine's half-life averages around 5 hours in healthy adults but varies widely between people, so after about 10 hours roughly a quarter of a mid-afternoon dose can still be circulating when you try to sleep. Even when it does not stop you falling asleep, late caffeine measurably reduces deep sleep, so you wake less rested. Cutting your last caffeine to around eight to ten hours before bed is one of the highest-value changes a heavy pre-workout or coffee drinker can make.

Alcohol is a sedative, so it can help you fall asleep faster, but that is where the benefit ends. As it clears overnight it fragments the second half of your sleep and suppresses REM, which is why a few drinks so often means waking at 3am unrefreshed. Removing alcohol close to bedtime is one of the clearest, best-evidenced ways to sleep more deeply.

Light is the master signal for your body clock: bright light in the evening, including from phones and bright rooms, delays melatonin release and pushes your sleep later. The flip side is that getting daylight early in the day helps anchor the rhythm so you feel sleepy at a sensible hour. Dimming lights in the last hour and keeping the bedroom dark and cool does more than any pill aimed at the same problem.

Magnesium contributes to normal functioning of the nervous system, normal psychological function, normal muscle function and the reduction of tiredness and fatigue. Some studies have looked at magnesium and sleep, mostly in older adults with low intakes, but there is no authorised health claim for magnesium and sleep. It is not a sedative.

ZMA is a fixed blend of zinc, magnesium and vitamin B6, often marketed for recovery, testosterone and sleep. None of the three has an authorised claim for sleep. Zinc contributes to the maintenance of normal testosterone levels in the blood, and magnesium and vitamin B6 contribute to the reduction of tiredness and fatigue, but that does not mean a blend improves sleep or raises testosterone in someone who is not short.

L-theanine is an amino acid found in tea. It is mostly studied alongside caffeine for focus. Research on sleep is small and mixed, and it has no authorised health claim. It is not a sedative.

Glycine is an amino acid. A few small studies have tested it before bed, with early and unsettled results. There is no authorised health claim for glycine and sleep.

Apigenin is a flavonoid found in chamomile. Chamomile tea has a long tradition as a bedtime drink, but human research on apigenin and sleep is limited and there is no authorised health claim. A warm caffeine-free drink can be part of a wind-down routine.

Montmorency tart cherry contains small amounts of melatonin and polyphenols. A few small studies have looked at sleep and muscle soreness after training, with modest and mixed results. There is no authorised health claim for tart cherry.

Valerian root has a long history of use. Research on sleep is inconsistent and product strength varies. In the UK, valerian products sold for sleep are usually registered traditional herbal medicines, so look for the THR mark and ask a pharmacist, especially if you take other medicines.

Melatonin is the hormone that signals night to your body, and it has solid evidence for circadian problems such as jet lag, shift work and delayed sleep phase, where a small, correctly-timed dose (often 0.5-1mg) shifts the clock. It is far less impressive for ordinary insomnia, where it mainly helps you fall asleep a little faster. The key UK point: melatonin is a prescription-only medicine here, not an over-the-counter supplement, so this is a conversation for a GP or pharmacist rather than an overseas order.

Ashwagandha has been studied for stress and sleep, mostly in small trials of standardised root extracts. There is no authorised health claim for ashwagandha in Great Britain. It is not suitable in pregnancy or breastfeeding, with thyroid, liver or autoimmune conditions, or alongside sedatives, thyroid or blood-sugar medicines, and there are rare reports of liver injury. Speak to your GP or pharmacist before taking it.

GABA is the brain’s primary calming neurotransmitter, which is why a GABA supplement sounds like it should work. The problem is that oral GABA does not cross the blood-brain barrier well, so very little of what you swallow reaches the brain where it would matter. The human sleep evidence is correspondingly weak, and any calm people feel is likely small or indirect. Your money goes further elsewhere on this page.

5-HTP is a serotonin precursor marketed for mood and sleep, but the direct evidence that it improves sleep is thin. More importantly, it raises serotonin, so combining it with antidepressants such as SSRIs or other serotonergic drugs carries a genuine risk of serotonin syndrome, which can be dangerous. Because of that interaction risk it is not a casual supplement to self-experiment with, and anyone on medication should not touch it without a clinician.

Most "night-time", "PM" or "sleep and recover" tubs are proprietary blends of exactly the modest or failed ingredients here, often underdosed and hidden so you cannot see how little of each you get. The worst are "night-time fat burners" that pair a token sleep ingredient with stimulant-free filler and an overnight-fat-loss claim that does not stand up. If a blend contains magnesium or ashwagandha, check the label dose against what you already take.