Head-to-head evidence comparison — which supplement is right for you?
L-Theanine wins 1 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
100-200mg
Morning with coffee for focus, Evening for relaxation, As needed for stress
Suntheanine® capsules or powder
200-350mg elemental magnesium daily
Evening for sleep/relaxation (glycinate), Morning for energy (malate), Anytime (citrate)
Depends on goal - see notes
30-60 minutes
30-60 minutes
30-60 minutes
Varies
1-2 weeks
1-2 weeks
1 week
Immediate
The effects of L-theanine consumption on sleep outcomes: A systematic review and meta-analysis
Sleep medicine reviews (2025) · Meta analysis · n=897
The findings indicate the potential use of L-theanine in the management of sleep disturbances; however, the lack of studies on "pure" L-theanine warrants further investigation.
Efficiency of Different Supplements in Alleviating Symptoms of ADHD with or Without the Use of Stimulants: A Systematic Review
Nutrients (2025) · Systematic review
The evidence revealed the potential use of supplements as complementary ADHD treatments under clinical guidance.
The Role of Supplements and Over-the-Counter Products to Improve Sleep in Children: A Systematic Review
International journal of molecular sciences (2023) · Systematic review
Although good sleep quality in children has been proven to be a key factor for optimal cognitive, physical and psychological development, a significant and ever-increasing percentage of the pediatric population suffers from sleep disorders.
Magnesium supplementation in pregnancy
The Cochrane database of systematic reviews (2014) · Meta analysis · n=9090
Women receiving magnesium were significantly less likely to require hospitalisation during pregnancy (RR 0.65, 95% CI 0.48 to 0.86; three trials, 1158 women).Of the 10 trials included in the review, only two were judged to be of high quality overall.
Magnesium sulphate and other anticonvulsants for women with pre-eclampsia
The Cochrane database of systematic reviews (2010) · Meta analysis · n=11444
It reduced the risk of placental abruption (RR 0.64, 95% CI 0.50 to 0.83; NNTB 100, 95% CI 50 to 1000), and increased caesarean section (RR 1.05, 95% CI 1.01 to 1.10).
Magnesium Supplementation and Blood Pressure: A Systematic Review and Meta-Analysis
Nutrients (2024) · Meta analysis · n=2709
38 RCTs with 2709 participants analyzed
L-Theanine has a higher evidence score (9/10 vs 8.5/10) and wins in 1 of 3 categories.
For improve deep sleep quality, Magnesium has a higher relevance score (90 vs 60).
No known interactions between L-Theanine and Magnesium have been documented in our database. However, always consult a healthcare provider before combining supplements.