“L-theanine with caffeine improves focus.”
L-theanine with caffeine gives a small, short-term boost on some attention tests, but how much theanine adds beyond caffeine alone is not established.
A theanine and caffeine product gives a small, short boost in focus, and most of that boost likely comes from the caffeine. These products are caffeine products, so count them toward your daily caffeine.
If you already drink coffee or tea, there is little reason to pay extra for added theanine.
Trials show small short-term attention benefits from the combination compared with a placebo, but a consistent added benefit over caffeine alone has not been established. Confidence is Limited because no trial was at low risk of bias and the main review was industry-funded.
L-theanine with caffeine gives a small, short-term boost on some attention tests, but how much theanine adds beyond caffeine alone is not established. Most of that boost probably comes from the caffeine.
A 2025 review of 50 trials pooled 15 of them. Compared with a placebo, theanine plus caffeine slightly improved accuracy on two attention tasks about 2 hours after a dose, while results for reaction time were unclear. When theanine alone was compared with caffeine alone, results leaned toward caffeine on most thinking tasks, though the differences were too uncertain to be sure, and the authors noted earlier work concluding that the attention benefit of the pair is likely due to the caffeine. A separate 2026 review found a single 200 mg dose of theanine alone sped up reaction times a little. No trial in the 2025 review was at low risk of bias, and the review was funded in part by a tea company.
- Payne ER, Aceves-Martins M, Dubost J, Greyling A, de Roos B. Effects of tea (Camellia sinensis) or its bioactive compounds l-theanine or l-theanine plus caffeine on cognition, sleep, and mood in healthy participants: a systematic review and meta-analysis of randomized controlled trials. Nutrition Reviews. 2025;83(10):1873-1891. DOI: 10.1093/nutrit/nuaf054. PMID: 40314930. PMCID: PMC12422004
- Gerolymos C, Saddier E, Boyer L, Fond G. Cognitive and affective effects of L-theanine: a systematic review and meta-analysis of 31 randomized trials. Molecular Psychiatry. 2026;31(11):6592-6602. DOI: 10.1038/s41380-026-03727-9. PMID: 42410082