PeptideFactSheetsAn independent reference
Menu

Stimulant and amino-acid combination · Fact sheet

Caffeine + L-theanine

Also known as Theanine/caffeine combination

Caffeine plus L-theanine has small controlled human studies showing improvements on some attention tasks. Effects vary by task and dose, and L-theanine does not reliably remove caffeine-related jitteriness.

Not FDA approvedModerate human evidence
Brain, mood & sleep

What is Caffeine + L-theanine?

Caffeine is a methylxanthine stimulant; L-theanine is an amino acid found in tea.

A capsule combination and brewed tea can deliver different amounts and accompanying compounds.

Benefits & claims

Interest centers on alertness with less perceived stimulation. The studies measure short-term task performance, not broad intelligence or treatment of ADHD.

What the evidence supports

  • A 44-person study of 97 mg theanine with 40 mg caffeine improved task-switching accuracy and alertness, but not all tested tasks.
  • A separate study improved task switching without a significant alertness benefit.
  • These acute findings do not establish sustained cognitive enhancement or protection from caffeine adverse effects.
Research areas
  • Acute attention
  • Task switching
  • Alertness

Dosage & frequency

Human study context

An acute cognition study supplies a single-exposure research reference, not a daily cognitive-treatment regimen.

2010 theanine/caffeine randomized study

44 young adults

Amount
L-theanine 97 mg plus caffeine 40 mg
Frequency
One study administration; assessments at 20 and 70 minutes
Route studied or labeled
Oral

Short-term laboratory outcomes only. The study does not establish daily frequency, long-term benefit, ADHD treatment or a universally optimal ratio.

Theanine/caffeine acute cognition trial
How to read these amounts

An approved regimen belongs to a specific product, indication, and population. A study regimen describes what researchers tested; it does not establish a prescription or a safe self-use protocol. Products, routes, and formulations are not interchangeable. A prescriber uses the full label and individual clinical circumstances.

Personal accounts may describe amounts, schedules and outcomes beyond clinical research. They do not establish a regimen. Read the reported experiences

Formulations, interactions & practical context

Identity and pharmacology
Caffeine is a methylxanthine stimulant; L-theanine is an amino acid found in tea.
Theanine/caffeine acute cognition trial Task-switching crossover study

Formulation differences

  • A capsule combination and brewed tea can deliver different amounts and accompanying compounds.

Interactions & precautions

  • The reviewed sources do not establish a comprehensive human interaction profile for this exact substance or combination.

What is still unresolved

  • Long-term functional benefit
  • Effects across different caffeine tolerance levels
  • Whether different ratios offer meaningful advantages
Theanine/caffeine acute cognition trial Task-switching crossover study Theanine and caffeine alone and together FDA: what approval means

Side effects & risks

  • Caffeine increased jitteriness and blood pressure in the 48-person study.
  • Sleep effects, tolerance and sensitivity depend on exposure and the individual; adding theanine does not guarantee protection.

This is a summary of the cited evidence, not a complete product label. A lack of human safety data does not establish safety.

Clinical research

Moderate human evidence

Acute randomized studies found task-specific attention effects. One 48-person study found that theanine did not significantly reduce caffeine-associated jitteriness.

Studies

Personal experiences

Reports describe what someone noticed. They cannot establish cause, typical results, or how often a side effect happens. Amounts and schedules describe the individual account, not an effective or safe dose. Product identity and strength may be unverified, and missing details are left explicit.

No attributable personal accounts were found in the sources reviewed.

Approval status

This combination is not an FDA-approved cognitive-enhancement treatment. Food or supplement availability is different from drug approval.

No FDA-approved product for this entry

Approval covers the labeled product, use and population. A trial phase does not establish success; a stopped program is not ongoing research.

Open questions

  • Long-term functional benefit
  • Effects across different caffeine tolerance levels
  • Whether different ratios offer meaningful advantages

Summary

These acute findings do not establish sustained cognitive enhancement or protection from caffeine adverse effects.

Sources

Medical evidence and regulatory sources are listed here. Personal reports are linked separately in the experiences section.

  1. pubmedTheanine/caffeine acute cognition trial

    44 participants; some task and alertness effects, other tasks unchanged.

  2. pubmedTask-switching crossover study

    Attention finding without significant subjective-alertness improvement.

  3. pubmedTheanine and caffeine alone and together

    48-person study including jitteriness and blood pressure.

  4. fdaFDA: what approval means

    Dietary supplements are not FDA-approved for safety and effectiveness before marketing.

How we assess sources · Suggest a correction