Found together in tea
Tea leaves contain both. Researchers test the pair to see whether it works differently from caffeine on its own.
Caffeine + L-theanine. What the research says about the pair, study by study.
Tea leaves contain both, and scientists have tested the two together in placebo-controlled trials for almost two decades. Here's what those trials tested and what they found.
7 studies cited, Peer-reviewed, Every study linked
Tea leaves naturally contain both caffeine and L‑theanine.
Per pouch
Ratio 2:1
- Caffeine
- 100 mg
- L‑theanine
- 50 mg
Summary
Key findings at a glance.
Attention and alertness
In placebo-controlled trials, people who took both scored better on attention tasks and rated themselves more alert*1–7.
Faster reactions
Several trials found people reacted faster and caught more targets on visual attention tests*2,3,7.
Both in every pouch
Every DIAL 50 pouch pairs 100 mg caffeine with 50 mg L‑theanine, printed right on the lid.
The ingredients
What caffeine and L-theanine are.
Caffeine is in coffee, tea, cacao and more. L‑theanine is an amino acid found in tea leaves. A cup of tea has both, and every DIAL 50 pouch pairs them too.
Coffea
Per pouch · 100 mg
Caffeine
The same stimulant that's in coffee and tea, at a measured dose that's printed right on the lid.
- Found in
- Coffee beans
- Tea leaves
- Cacao
- Guarana
- Yerba mate
- What it does
- Through the day, a compound called adenosine builds up and tells your brain you're tired. Caffeine blocks that signal, which helps you feel alert and energized*.
Camellia sinensis
Per pouch · 50 mg
L‑theanine
An amino acid found naturally in tea leaves, and caffeine's classic partner.
- Found in
- Green tea
- Black tea
- Oolong tea
- White tea
- What it does
- Pairs with caffeine to support calm, clear focus*.
Findings
What the studies found.
Trials gave people caffeine, L‑theanine, both or a placebo, then measured attention, reaction time and mood. Here's what they found for the pair.
Attention
Switching between tasks
People who took the pair were more accurate when switching between tasks*1,4–6 and, in one trial, less thrown by distractions*1.
Speed
Reaction time and accuracy
They also reacted faster and caught more targets on visual attention tests*2,3,7.
Mood
Self-rated alertness
On questionnaires, people rated themselves more alert than on a placebo*2,4,6.
Every study, with its doses and findings.
#StudyTestedWhat it found
1Owen et al., 2008Nutr Neurosci50 mg caffeine + 100 mg L‑theanineThe pair improved speed and accuracy when switching between tasks, and made people less prone to distraction on a memory task.
2Haskell et al., 2008Biol Psychol150 mg caffeine + 250 mg L‑theanineThe pair improved accuracy on a visual attention task, sped up reaction times and raised alertness ratings compared with placebo.
3Kelly et al., 2008J Nutr50 mg caffeine + 100 mg L‑theanineThe pair raised hit rates and target discrimination on an attention task compared with placebo.
4Giesbrecht et al., 2010Nutr Neurosci40 mg caffeine + 97 mg L‑theanineThe pair improved accuracy when switching tasks and raised self-rated alertness.
5Einöther et al., 2010Appetite40 mg caffeine + 97 mg L‑theanineThe pair improved attention on a task-switching test.
6Camfield et al., 2014Nutr RevReview of 11 placebo-controlled trialsPooling the trials, the pair showed moderate effects on alertness and task-switching accuracy in the first two hours.
7Kahathuduwa et al., 2017Nutr Neurosci160 mg caffeine + 200 mg L‑theanineThe pair sped up reactions on a recognition task and produced a stronger attention-related brain response than either ingredient alone.
Summaries are drawn from each study's published abstract. Full citations are in the references below.
Try DIAL 50.
100 mg caffeine and 50 mg L-theanine in every pouch. Every order ships free.
One-time purchase · Free shipping
Sources
References
Every study cited on this page, with the doses each one tested.
Owen GN, Parnell H, De Bruin EA, Rycroft JA. The combined effects of L‑theanine and caffeine on cognitive performance and mood. Nutr Neurosci. 2008;11(4):193-8.
Tested 50 mg caffeine + 100 mg L‑theaninedoi:10.1179/147683008X301513 (opens in a new tab)
Haskell CF, Kennedy DO, Milne AL, Wesnes KA, Scholey AB. The effects of L‑theanine, caffeine and their combination on cognition and mood. Biol Psychol. 2008;77(2):113-22.
Tested 150 mg caffeine + 250 mg L‑theaninedoi:10.1016/j.biopsycho.2007.09.008 (opens in a new tab)
Kelly SP, Gomez-Ramirez M, Montesi JL, Foxe JJ. L‑theanine and caffeine in combination affect human cognition as evidenced by oscillatory alpha-band activity and attention task performance. J Nutr. 2008;138(8):1572S-1577S.
Tested 50 mg caffeine + 100 mg L‑theaninedoi:10.1093/jn/138.8.1572S (opens in a new tab)
Giesbrecht T, Rycroft JA, Rowson MJ, De Bruin EA. The combination of L‑theanine and caffeine improves cognitive performance and increases subjective alertness. Nutr Neurosci. 2010;13(6):283-90.
Tested 40 mg caffeine + 97 mg L‑theaninedoi:10.1179/147683010X12611460764840 (opens in a new tab)
Einöther SJ, Martens VE, Rycroft JA, De Bruin EA. L‑theanine and caffeine improve task switching but not intersensory attention or subjective alertness. Appetite. 2010;54(2):406-9.
Tested 40 mg caffeine + 97 mg L‑theaninedoi:10.1016/j.appet.2010.01.003 (opens in a new tab)
Camfield DA, Stough C, Farrimond J, Scholey AB. Acute effects of tea constituents L‑theanine, caffeine, and epigallocatechin gallate on cognitive function and mood: a systematic review and meta-analysis. Nutr Rev. 2014;72(8):507-22.
Tested Review of 11 placebo-controlled trialsdoi:10.1111/nure.12120 (opens in a new tab)
Kahathuduwa CN, Dassanayake TL, Amarakoon AMT, Weerasinghe VS. Acute effects of theanine, caffeine and theanine-caffeine combination on attention. Nutr Neurosci. 2017;20(6):369-377.
Tested 160 mg caffeine + 200 mg L‑theaninedoi:10.1080/1028415X.2016.1144845 (opens in a new tab)