Thorne Magnesium BisglycinatevsNOW Foods Glycine Pure Powder

Magnesium acts as a cofactor in hundreds of enzymatic reactions and helps regulate neurotransmitter systems, including blunting excitatory NMDA-receptor activity and supporting inhibitory GABA tone. The bisglycinate (chelated) form binds magnesium to the amino acid glycine, which improves absorption and reduces the laxative effect seen with oxide or citrate, while glycine itself has mild calming properties.

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.

Evidence is real but moderate. A 2025 randomized, placebo-controlled trial of magnesium bisglycinate in adults with poor sleep found a statistically significant reduction in Insomnia Severity Index at four weeks, though with a small effect size (Cohen's d around 0.2). An earlier double-blind trial in older adults reported improved sleep time and efficiency at 500 mg daily, and a 2021 meta-analysis found about a 17-minute reduction in sleep onset latency while noting the overall literature quality is limited.

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.

The most common issue is loose stools or mild GI upset, which is less likely with the bisglycinate form than with oxide. Excess magnesium is normally cleared by the kidneys, so people with reduced kidney function risk accumulation and should avoid supplementing without medical supervision. This is educational information, not medical advice; individual results vary.

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.

Expect roughly $40-$44 for a 60-serving jar as of 2026, which is mid-range for a certified chelate. Generic magnesium oxide or citrate costs a fraction as much but is less absorbable and harsher on the gut. Subscribe-and-save on Thorne.com trims about 10%, and the product is frequently HSA/FSA eligible.

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.

Adults seeking general relaxation and sleep support. Not appropriate without medical guidance for people with significant kidney impairment, heart block, or those on certain medications (such as some antibiotics or bisphosphonates) where magnesium can affect absorption. Pregnant or nursing people should consult a clinician.

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.