NOW Foods Glycine Pure PowdervsMomentous Sleep

Glycine is both a building-block amino acid and an inhibitory neurotransmitter in the central nervous system. Taken before bed, research suggests it promotes peripheral vasodilation that lowers core body temperature - a physiological signal closely tied to sleep onset - and acts on NMDA receptors in the suprachiasmatic nucleus, the brain's master clock. The net effect in studies was faster sleep onset and improved sleep quality without altering overall sleep architecture.

Momentous Sleep does not sedate you the way melatonin or prescription sleep drugs do; instead it is formulated to nudge the brain toward calm and support sleep-stage quality. L-theanine (200mg) is associated with increased alpha brain-wave activity linked to wakeful relaxation and with modulation of GABA, serotonin, and dopamine signaling, which may ease the wind-down before bed. Magnesium L-threonate (2,000mg of Magtein, providing ~145mg elemental magnesium) is one of the few magnesium forms shown in animal work to raise brain magnesium levels by crossing the blood-brain barrier, where magnesium is involved in NMDA/GABA balance and the regulation of neural excitability and sleep. Apigenin (50mg), a plant flavonoid, binds the benzodiazepine site of the GABA-A receptor in laboratory studies, the same calming system targeted by some sleep medications, though its behavioral effects in animals are mixed. Together the stack is designed to lower pre-sleep arousal and support deeper sleep rather than knock you out.

The headline evidence is a 2007 study by Yamadera and colleagues in which 3 g of glycine before bed improved subjective sleep quality and shortened the time to fall asleep and to reach slow-wave sleep on polysomnography in people with unsatisfactory sleep; it also reduced daytime sleepiness and improved a memory task. Follow-up work from the same group reported reduced fatigue and better next-day performance after sleep restriction. The caveat is that these trials are small and largely from a single research program, so the evidence, while encouraging, is far from definitive.

Evidence is ingredient-by-ingredient and supportive but not uniform. Magnesium L-threonate: a 2024 randomized, double-blind, placebo-controlled trial in Sleep Medicine: X (80 adults aged 35-55 with self-reported sleep problems, 1g/day for 21 days) found Oura-measured improvements in deep-sleep (p<0.001) and REM-sleep (p=0.020) scores versus placebo; a separate 2025 randomized, double-blind trial in Frontiers in Nutrition using 2g Magtein daily for 6 weeks (100 adults aged 18-45) reported significant cognitive gains and improved self-reported sleep-related impairment, but no significant difference on objective Oura sleep metrics. Note the product's 2g daily dose is higher than the 1g used in the deep/REM-sleep trial. L-theanine: a 2019 randomized, double-blind, placebo-controlled crossover trial in Nutrients (n=30, 200mg/day, 4 weeks) found significantly improved Pittsburgh Sleep Quality Index scores along with reduced anxiety and depression scores. Apigenin is the weakest link: there are essentially no published human trials of isolated apigenin at 50mg for sleep; the closest human evidence comes from multi-compound chamomile extracts, and a 2011 pilot RCT in BMC Complementary and Alternative Medicine (n=34, 540mg/day) found no statistically significant improvement on its primary sleep-diary outcomes, only small-to-moderate non-significant trends. No published trial has tested this exact three-ingredient combination.

Glycine is exceptionally well tolerated because it is an amino acid the body already uses in large amounts; the most that sensitive users tend to report is mild stomach upset or soft stools at high intakes. As with any supplement, start at the studied dose rather than exceeding it. This is educational information, not medical advice; individual results vary.

Generally well tolerated at the studied doses. The most likely issue is gastrointestinal upset or loose stools from magnesium, though L-threonate is usually gentler on the gut than magnesium citrate or oxide and the elemental dose here (~145mg) is modest. L-theanine has a strong safety record with few adverse events reported in trials. Some users report feeling mildly groggy or having unusually vivid dreams the next morning, and a minority notice no effect at all. Serious effects are uncommon at these doses, but magnesium can accumulate in people with impaired kidney function, and grapefruit-derived compounds such as the apigenin used here can theoretically interact with the CYP enzymes that metabolize certain medications. Stop and consult a clinician if you experience persistent diarrhea, dizziness, low-blood-pressure symptoms, or any new reaction, and talk to a doctor before combining it with prescription medications.

At about $29.99 list (and frequently under $25 at third-party retailers) for a 1 lb tub, and a studied dose of roughly 3 g, you get on the order of 150 bedtime servings - pennies per night. That makes glycine one of the lowest-cost ways to run a personal sleep experiment.

As of 2026, a 30-serving pack runs about $109.95 at full price direct from Momentous, dropping to roughly $82.46 with the 25% subscribe-and-save discount, which works out to about $2.75 to $3.65 per night. Third-party retailers such as Amazon and Vitacost have listed it higher, around $124. This is a dietary supplement, so it is not covered by health insurance and is not eligible for typical insurance reimbursement; HSA/FSA eligibility varies by plan and is not guaranteed, so confirm before assuming. The cheapest way to lower the cost is the subscription; buying the three ingredients separately as generics would be far less expensive but without the NSF certification or single-pack convenience.

Generally healthy adults curious about a low-risk sleep-quality aid. People who are pregnant or nursing, or who have a serious medical condition or take prescription medication, should consult a clinician first. It is not intended to treat diagnosed insomnia or any sleep disorder.

Best for healthy adults seeking better sleep quality, depth, and next-day clarity without melatonin, and especially for drug-tested athletes who need an NSF Certified for Sport product. It suits people whose main issue is a racing mind or shallow sleep rather than a circadian-rhythm or shift-work problem (where melatonin may be more appropriate). Who should avoid or consult a clinician first: anyone pregnant or breastfeeding; people with kidney disease (magnesium is cleared by the kidneys and can accumulate when kidney function is impaired); those on blood-pressure, sedative, or stimulant medications; anyone with a known grapefruit sensitivity, since the apigenin here is grapefruit-derived and grapefruit compounds can affect drug-metabolizing enzymes; and people with diagnosed insomnia or sleep apnea, who need medical evaluation. Supplements are not FDA-approved to diagnose, treat, or cure any sleep disorder.