The newest magnesium bisglycinate sleep trial, the older one in seniors, what L-theanine did in 4 weeks, and the NIH upper limit.
Key Takeaways
- In a 2024 trial of 155 adults with poor sleep, magnesium bisglycinate improved insomnia scores slightly more than placebo. The effect was small.
- An earlier trial in older adults found a larger improvement, but it used a different form, magnesium oxide.
- In a 4-week crossover trial, 200 mg a day of L-theanine improved several sleep measures compared with placebo.
- Cort-Relax provides 400 mg magnesium and 150 mg L-theanine. The NIH upper limit for magnesium from supplements is 350 mg a day for adults.
Why Magnesium Form Matters
Magnesium is involved in hundreds of enzyme reactions, including those that help the nervous system settle. Bisglycinate binds magnesium to two molecules of glycine. It tends to be gentler on the stomach than oxide, the cheap form in many older studies.
The 2025 Bisglycinate Trial
Researchers randomly assigned 155 healthy adults with poor sleep to magnesium bisglycinate (250 mg elemental magnesium a day) or placebo for 4 weeks. The trial had no commercial sponsor. Both groups improved on the Insomnia Severity Index, and the magnesium group improved a little more.
L-Theanine
L-theanine is the amino acid in green tea. In a double-blind crossover trial, 30 healthy adults took 200 mg a day or placebo for 4 weeks each. Compared with placebo, L-theanine produced larger improvements in sleep latency, sleep disturbance and the use of sleep medicine on the Pittsburgh Sleep Quality Index (p=0.0099, 0.0184 and 0.047). Verbal fluency and executive function scores also improved after L-theanine.
How Our Doses Compare
| What Was Measured | Amount Studied | DLNIA Amount |
|---|---|---|
| Magnesium, sleep trial (2024) | 250 mg elemental as bisglycinate | 400 mg (bisglycinate 300 mg, citrate 50 mg, malate 50 mg) |
| L-theanine, sleep and stress trial (2019) | 200 mg a day | 150 mg |
| NIH upper limit, supplemental magnesium (adults) | 350 mg a day | 400 mg: see note above |
What the Research Does Not Show
The effects on sleep in these trials were modest. None of them tested our exact formula, and the 2012 study used a different form of magnesium. If you have kidney problems or take antibiotics, bisphosphonates or diuretics, ask your doctor before taking magnesium.
References
- Schuster J, et al. Magnesium bisglycinate supplementation in healthy adults reporting poor sleep: a randomized, placebo-controlled trial. Nat Sci Sleep. 2025;17:2027–2040. PubMed · DOI: 10.2147/NSS.S524348
- Abbasi B, et al. The effect of magnesium supplementation on primary insomnia in elderly: A double-blind placebo-controlled clinical trial. J Res Med Sci. 2012;17(12):1161–1169. PubMed
- Hidese S, et al. Effects of L-theanine administration on stress-related symptoms and cognitive functions in healthy adults: a randomized controlled trial. Nutrients. 2019;11(10):2362. DOI: 10.3390/nu11102362
- NIH Office of Dietary Supplements. Magnesium: Fact Sheet for Consumers. National Institutes of Health. Read the fact sheet