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L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance
Open accessAbstract
Recent neuropharmacological research has suggested that certain constituents of tea may have modulatory effects on brain state. The bulk of this research has focused on either L-theanine or caffeine ingested alone (mostly the latter) and has been limited to behavioral testing, subjective rating, or neurophysiological assessments during resting. Here, we investigated the effects of both L-theanine and caffeine, ingested separately or together, on behavioral and electrophysiological indices of tonic (background) and phasic (event-related) visuospatial attentional deployment. Subjects underwent 4 d of testing, ingesting either placebo, 100 mg of L-theanine, 50 mg of caffeine, or these treatments combined. The task involved cued shifts of attention to the left or right visual hemifield in anticipation of an imperative stimulus requiring discrimination. In addition to behavioral measures, we examined overall, tonic attentional focus as well as phasic, cue-dependent anticipatory attentional biasing, as indexed by scalp-recorded alpha-band (8-14 Hz) activity. We found an increase in hit rate and target discriminability (d') for the combined treatment relative to placebo, and an increase in d' but not hit rate for caffeine alone, whereas no effects were detected for L-theanine alone. Electrophysiological results did not show increased differential biasing in phasic alpha across hemifields but showed lower overall tonic alpha power in the combined treatment, similar to previous findings at a larger dosage of L-theanine alone. This may signify a more generalized tonic deployment of attentional resources to the visual modality and may underlie the facilitated behavioral performance on the combined ingestion of these 2 major constituents of tea.
Overview
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Written from the paper’s full text.
TL;DR
In a four-day repeated-measures study, combined L-theanine (100 mg) and caffeine (50 mg) improved visuospatial attention performance and reduced tonic alpha-band EEG power relative to placebo. Caffeine alone improved discriminability but not hit rate, while L-theanine alone at this lower dose produced no significant behavioral or tonic-alpha effects.
Key findings
- The combined treatment increased hit rate and target discriminability relative to placebo; the hit-rate improvement was about 3%, and the discriminability effect size was larger for the combination (Cohen’s d = 0.55) than for caffeine alone (d = 0.42).
- Caffeine alone improved discriminability relative to placebo but did not improve hit rate; no treatment affected reaction time.
- L-theanine alone at 100 mg produced no significant behavioral effects and did not significantly lower tonic alpha, unlike prior findings at 250 mg.
- Tonic alpha power was significantly lower for the combined treatment than placebo; the alpha cueing effect was smaller for caffeine alone than placebo, but not for L-theanine alone or the combination.
Methods
- Sixteen neurologically normal paid volunteers (5 female; ages 21–40, mean 27.5 years) completed four counterbalanced testing days, receiving placebo, 100 mg L-theanine, 50 mg caffeine, or both combined, with task runs beginning 30 min after ingestion.
- Participants performed a cued visuospatial attention task requiring covert shifts to left or right locations and discrimination of target versus standard stimuli, while continuous EEG was recorded from 164 scalp electrodes plus EOG.
- Behavioral analyses used hit rate, false alarm rate, discriminability index, and reaction time; EEG analyses examined tonic alpha amplitude before cue onset and lateralized anticipatory alpha after cue onset using temporal spectral evolution.
Limitations
- The authors caution that synergy between L-theanine and caffeine cannot be strongly claimed because only single doses were tested and the combined condition did not differ significantly from caffeine alone on tonic alpha.
- The authors note that alpha effects of both compounds appear dose-dependent and call for future dose-response characterization; the caffeine-alone alpha reduction did not reach significance (P = 0.18).
- The unexpected reduction in the alpha cueing effect for caffeine alone is described as needing replication; more generally, the small sample and single-dose design limit generalization.
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Claims the paper makes
16 Own result · 9 No full text of the sources · 8 Own method · 8 Own interpretation · 1 Supported so far · 1 Partly supported · accuracy not yet measured
The sources with a verdict support this claim; the rest weren’t checked yet, have no full text we could read, or their verdicts aren’t rated yet.
In the paper
“Using electroencephalographic (EEG) recordings in humans, Kobayashi et al. (12) and Juneja et al. (13) reported that activity within the alpha frequency band (8-14 Hz) increased in reaction to L-theanine ingestion when measured during a state of rest.”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > Introduction
What the sources say
- Supportedcites [12] Kobayashi, 1998, Effects of L-theanine on the release of α-brain waves in human volunteers, Nihon Nogeikagaku Kaishi. source
The experimental results report increased alpha-wave activity after L-theanine ingestion in eight human volunteers. The methods describe EEG recordings while participants sat in a controlled room, consistent with measurement at rest (methods and results, indexed under Abstract, pp. 155–157). (LLM, conf=0.90)
- Not checked — no full text of the sourcecites [13] Juneja, 1999, L-Theanine—a unique amino acid of green tea and its relaxation effect in humans, Trends Food Sci Technol. source
plaindirect- Asserted: passes — The authors put it forward as true.
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- Supported
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Follow-up t-tests revealed that alpha was significantly lower for T1C than P (P , 0.02).”
- Also stated in: § Abstract · plain
“showed lower overall tonic alpha power in the combined treatment”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > ).
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
- Also stated in: § Abstract · plain
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Behavioral performance was significantly improved on the combined treatment (T1C) in terms of hit rate (P , 0.016) and d# (P , 0.002).”
- Also stated in: § Abstract · plain
“We found an increase in hit rate and target discriminability (d#) for the combined treatment relative to placebo”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > Results
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
- Also stated in: § Abstract · plain
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“P did not differ from either T or C (see Fig. 2).”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > ).
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“There was also a significant improvement in d# on C compared with P (P , 0.016), but not in hit rate.”
- Also stated in: § Abstract · plain
“and an increase in d# but not hit rate for caffeine alone”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > Results
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
- Also stated in: § Abstract · plain
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The typical alpha cueing effect was readily apparent in both the nonnormalized alpha amplitude waveforms and normalized pretarget measures (Fig. 3) for each treatment day.”
- Also stated in: § ). · boosted
“A strong attention 3 hemisphere interaction (P , 0.0005) was found on the pretarget anticipatory alpha measures as expected, reflecting the typically observed alpha-mediated cueing effect.”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > ).
boostedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
- Also stated in: § ). · boosted
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Behavioral performance was significantly improved on the combined treatment (T1C) in terms of hit rate (P , 0.016) and d# (P , 0.002).”
- Also stated in: § Abstract · plain
“We found an increase in hit rate and target discriminability (d#) for the combined treatment relative to placebo”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > Results
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
- Also stated in: § Abstract · plain
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“There was also a significant improvement in d# on C compared with P (P , 0.016), but not in hit rate.”
- Also stated in: § Abstract · plain
“and an increase in d# but not hit rate for caffeine alone”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > Results
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
- Also stated in: § Abstract · plain
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In addition, there was a significant 3-way interaction among treatment, attention, and hemisphere (P , 0.05).”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > ).
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“When we reduced the alpha cueing effect to a single metric as described above, the effect was smaller on C than P (P , 0.02) but did not differ for the T or T1C conditions.”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > ).
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
- Probably not a substantial claim. 12
- The quote only partly states this claim. 1
- It may state two separate claims as one. 9
The cited sources support only part of this claim — read each source’s verdict below.
In the paper
“Previous studies have reported a drop in absolute alpha power during resting with eyes open on ingestion of caffeine at higher dosages, e.g., 200 mg (30) and 400 mg (31).”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > Discussion
What the sources say
- Supportedcites [30] Siepmann, 2002, Effects of caffeine on topographic quantitative EEG, Neuropsychobiology. source
The citation to this paper is attached to the 200 mg dose, not the separate 400 mg dose. The Abstract describes EEG recording during relaxation with eyes open, and the Results report significantly reduced absolute slow- and fast-alpha power after caffeine under that condition. (LLM, conf=0.94)
- Partly supportedcites [31] Deslandes, 2005, Effects of caffeine on the electrophysiological, cognitive and motor responses of the central nervous system, Braz J Med Biol Res. sourceExperimental — accuracy not yet measured
The Abstract reports that 400 mg of caffeine significantly reduced alpha absolute power, but specifies that the resting EEG was recorded with eyes closed. The Quantitative electroencephalographic analyses section distinguishes this study's eyes-closed condition from earlier studies with significant results in subjects tested with eyes open. This source therefore supports the 400 mg reduction, not the claimed eyes-open condition. (LLM, conf=0.90)
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
- Supported
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“There were no significant effects of L-theanine, and no effects of any of the 3 treatments on RT”
- Also stated in: § Abstract · plain
“whereas no effects were detected for L-theanine alone.”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > Results
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
The quote only partly states this claim.
- Rests on an assumption: A typical serving of tea contains roughly 100 mg L-theanine and 50 mg caffeine.
- Also stated in: § Abstract · plain
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“When we reduced the alpha cueing effect to a single metric as described above, the effect was smaller on C than P (P , 0.02) but did not differ for the T or T1C conditions.”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > ).
plain- Asserted: passes — The authors put it forward as true.
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It may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Thus, a normalization of these measures was necessary to remove the variance caused by practice, and this was carried out by transforming each data point to a z-score with respect to the mean and SD of all scores measured on that day (d 1, d 2, d 3, d 4).”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > Methods
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
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Probably not a substantial claim.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“A tentative interpretation of the current pattern of results is that L-theanine works to enhance the tonic apportionment of attentional resources to the visual modality and does so to a significant degree when a large dosage is ingested by itself or in combination with caffeine when a smaller dosage is ingested.”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > Discussion
hedgeddirect- Asserted: passes — The authors put it forward as true.
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It may state two separate claims as one.
A claim is checked only against the cited paper’s full text, never its abstract, and none is available for its sources.
In the paper
“This was of interest to the attention community, as the alpha rhythm has long been known to be sensitive to overall attentional states (i.e., intensity aspects such as arousal) (14) and, further, is involved in the biasing of selective attention (15,16).”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > Introduction
What the sources say
- Not checked — no full text of the sourcecites [14] Adrian, 1934, The Berger Rhythm: Potential changes in the occipital lobes in man, Brain. source
- Not checked — no full text of the sourcecites [15] Foxe, 1998, Parieto-occipital ∼10 Hz activity reflects anticipatory state of visual attention mechanisms, Neuroreport. source
- Not checked — no full text of the sourcecites [16] Kelly, 2006, Increases in alpha oscillatory power reflect an active retinotopic mechanism for distracter suppression during sustained visuospatial attention, J Neurophysiol. source
boostedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
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Probably not a substantial claim. It may state two separate claims as one.
In the paper
“Haskell et al. (33) administered a large battery of cognitive tests before and after consumption of a drink containing either placebo, 250 mg of L-theanine, 150 mg of caffeine, or their combination.These authors found improvements in simple and numeric working memory RT, sentence verification accuracy, and alertness ratings for the combined treatment but not for either treatment alone.”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > Discussion
What the sources say
- Not checked — no full text of the sourcecites [33] Haskell, 2008, The effects of L-theanine, caffeine and their combination on cognition and mood, Biol Psychol. source
plaindirect- Asserted: passes — The authors put it forward as true.
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- Load-bearing: passes — The paper’s conclusions depend on it.
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It may state two separate claims as one.
In the paper
“Parnell et al. (32) reported improved speed and accuracy on an attention-switching task at 60 min and reduced susceptibility to distracting information during a memory task at both 60 and 90 min following ingestion of a combination of L-theanine and caffeine in the same dosages as used here.”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > Discussion
What the sources say
- Not checked — no full text of the sourcecites [32] Parnell, 2006, Combined effects of L-theanine and caffeine on cognition and mood, Appetite. source
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
In the paper
“Using a similar crossover design but with a greater dosage of caffeine (250 mg) than L-theanine (200 mg), Rogers et al. (34) found that L-theanine tended to counteract the caffeine-induced rise in blood pressure but did not interact with caffeine-induced increases in either alertness or ''jitteriness'' on state anxiety scales.”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > Discussion
What the sources say
- Not checked — no full text of the sourcecites [34] Rogers, 2008, Time for tea: mood, blood pressure and cognitive performance effects of caffeine and L-theanine administered alone and together, Psychopharmacology (Berl). source
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“A 4-d balanced repeated-measures design was employed, with subjects receiving 1 of the 4 treatments (including placebo) on each day in counterbalanced order.”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > Statistical methods.
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. It may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Subjects were uninformed of the treatment, which was served in 100 mL of water, with the placebo treatment consisting only of water.”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > Methods
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
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Probably not a substantial claim.
- Rests on an assumption: L-theanine and caffeine are tasteless when dissolved in water.
In the paper
“In addition, tonic (background) alpha amplitude was relatively decreased for L-theanine, in apparent contradiction to the findings of Juneja et al. (13).”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > Introduction
What the sources say
- Not checked — no full text of the sourcecites [13] Juneja, 1999, L-Theanine—a unique amino acid of green tea and its relaxation effect in humans, Trends Food Sci Technol. source
hedgeddirect- Asserted: fails — The authors may not put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: fails — The paper may give no reason why it holds.
Probably not a substantial claim. The authors may not put it forward as true. The paper’s conclusions may not depend on it. The paper may give no reason why it holds.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Because 3 t-tests were performed including the same placebo data, we applied a Bonferronicorrected a-level of 0.016 here.”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > Statistical methods.
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“EEG data were epoched from 2300 ms before to 1100 ms after cue onset and baseline-corrected relative to the interval 2100 to 0 ms, with an artifact rejection threshold of 6100 mV applied.”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > Methods
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Based on a calibrated mapping of EOG amplitude to visual angle, trials were rejected off-line if eye gaze deviated by .0.5° during the cue-target interval.”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > Methods
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“This study marks the third finding of decreased alpha as a result of L-theanine ingestion (albeit a partial cause here) to date, demonstrating the reliability of the effect.”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > Discussion
boosteddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Subjects underwent 4 d of testing, ingesting either placebo, 100 mg of L-theanine, 50 mg of caffeine, or these treatments combined.”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > Abstract
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
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Probably not a substantial claim.
- Rests on an assumption: L-theanine and caffeine are tasteless when dissolved in water.
A claim is checked only against the cited paper’s full text, never its abstract, and none is available for its sources.
In the paper
“In intersensory attention tasks, where the relevant modality is cued ;1 s before a compound audiovisual target stimulus, parieto-occipital alpha power in the intervening period is increased for attend-visual trials relative to attend-auditory trials (15,17).”
§ L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance 1-3 > Introduction
What the sources say
- Not checked — no full text of the sourcecites [15] Foxe, 1998, Parieto-occipital ∼10 Hz activity reflects anticipatory state of visual attention mechanisms, Neuroreport. source
- Not checked — no full text of the sourcecites [17] Fu, 2001, Attention-dependent suppression of distracter visual input can be cross-modally cued as indexed by anticipatory parieto-occipital alpha-band oscillations, Brain Res Cogn Brain Res. source
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim.
The paper relies on this without support.
A typical serving of tea contains roughly 100 mg L-theanine and 50 mg caffeine.
“An immediate question, given this replication, is whether this tonic alpha reduction occurs at lower dosages of L-theanine, closer to the amount ingested through a typical serving of tea.In the present study, we administered a lower dosage of 100 mg to address this.”
The paper relies on this without support.
L-theanine and caffeine are tasteless when dissolved in water.
“Both theanine and caffeine are tasteless in water solution.”
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
The cited source doesn’t support the claim as written.
In the citing paper
“whereas in active and anticipatory conditions, studies have shown that theanine reduced alpha power at 100 mg,62”
From 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 (2025) · cites this paper as [62]
Checked by a reasoning model — may be wrong.
Experimental — accuracy not yet measuredThe source backs part of the claim, not all of it — or backs it for a different population, condition or comparison.
In the citing paper
“Caffeine has been known for decades to improve sustained attention in healthy adults (e.g. Refs.25–27, animal models with ADHD28 and even individuals with ADHD29,30.”
From Effects of l-theanine–caffeine combination on sustained attention and inhibitory control among children with ADHD: a proof-of-concept neuroimaging RCT (2020) · cites this paper as [25]
Experimental — accuracy not yet measuredThe cited source says what the claim attributes to it.
In the citing paper
“This is contrary to previous findings (Einother et al. 2010; Haskell et al. 2008; Kelly et al. 2008; Owen et al. 2008)”
From A Double-Blind, Placebo-Controlled Study Evaluating the Effects of Caffeine and L-Theanine Both Alone and in Combination on Cerebral Blood Flow, Cognition and Mood (2015) · cites this paper as Kelly et al. 2008
The cited source says what the claim attributes to it.
In the citing paper
“Individual studies have, however, suggested that co-ingestion of caffeine and L-theanine may have an additive effect, with additional benefits noted compared to when each is administered in isolation (20–27), although such findings have been somewhat inconsistent (28, 29) and would benefit from further behavioral and mechanistic evaluation.”
From Effects of L-theanine on cognition, mood and sleep: evidence from human trials (2026) · cites this paper as [24]
In the citing paper
“Likewise, improvements in cognitive performance, subject alertness and complex senses interactions have also been documented [62][63][64].”
From l-Theanine as a Functional Food Additive: Its Role in Disease Prevention and Health Promotion (2016) · cites this paper as [62]
Citations
Cites
EEG alpha and theta oscillations reflect cognitive and memory performance: a review and analysis
Klimesch, W. (1999) · Brain Research Reviews · doi:10.1016/s0165-0173(98)00056-3 · Cited by 6,889
Über das Elektrenkephalogramm des Menschen
Berger, H. (1929) · European Archives of Psychiatry and Clinical Neuroscience · doi:10.1007/bf01797193 · Cited by 4,266
EEG alpha oscillations: The inhibition–timing hypothesis
Klimesch, W., Sauseng, P., & Hanslmayr, S. (2006) · Brain Research Reviews · doi:10.1016/j.brainresrev.2006.06.003 · Cited by 3,890
Fredholm, B. B., Bättig, K., Holmén, J., Nehlig, A., & Zvartau, E. E. (1999) · Pharmacological Reviews · doi:10.1016/s0031-6997(24)01396-6 · Cited by 2,624 · cited 1×
“Although caffeine (1,3,7-trimethylxanthine) is by far the constituent most studied, with findings of increased alertness and speeded reaction time (RT)(4) predominant (5,6), there exists evidence that caffeine alone cannot fully account for the positive effects of tea drinking.”
BackgroundThut, G., Nietzel, A., Brandt, S., & Pascual-Leone, Á. (2006) · Journal of Neuroscience · doi:10.1523/jneurosci.0875-06.2006 · Cited by 1,662
THE BERGER RHYTHM: POTENTIAL CHANGES FROM THE OCCIPITAL LOBES IN MAN
ADRIAN, E. D., & MATTHEWS, B. H. C. (1934) · Brain · doi:10.1093/brain/57.4.355 · Cited by 1,396
Worden, M. S., Foxe, J. J., Wang, N., & Simpson, G. V. (2000) · The Journal of Neuroscience · doi:10.1523/jneurosci.20-06-j0002.2000 · Cited by 1,268
Self-citationEffects of caffeine on human behavior
Smith, A. (2002) · Food and Chemical Toxicology · doi:10.1016/s0278-6915(02)00096-0 · Cited by 741
Kelly, S. P., Lalor, E. C., Reilly, R. B., & Foxe, J. J. (2006) · Journal of Neurophysiology · doi:10.1152/jn.01234.2005 · Cited by 715
Self-citationRihs, T. A., Michel, C. M., & Thut, G. (2007) · European Journal of Neuroscience · doi:10.1111/j.1460-9568.2007.05278.x · Cited by 586
Cited by
Sorted by citations
EEG frequency bands in psychiatric disorders: a review of resting state studies
Newson, J. J., & Thiagarajan, T. C. (2019) · Frontiers in Human Neuroscience · doi:10.3389/fnhum.2018.00521 · Cited by 863
Saeed, M., Naveed, M., Arif, M. A., Kakar, M. U., Manzoor, R., El-Hack, M. E. A., Alagawany, M. M., Tiwari, R., Khandia, R., Munjal, A. K., et al. (2017) · Biomedicine & Pharmacotherapy · doi:10.1016/j.biopha.2017.09.024 · Cited by 246
Bioactive components of tea: Cancer, inflammation and behavior
de Mejı́a, E. G., Ramı́rez-Mares, M. V., & Puangpraphant, S. (2009) · Brain Behavior and Immunity · doi:10.1016/j.bbi.2009.02.013 · Cited by 232
“Matching electroencephalographic recordings with cognitive task performance, it has been demonstrated that the unique tea amino acid theanine plays a role in attentional processing, in synergy with caffeine, enhancing cognition in humans (Kelly et al., 2008).”
Caffeine as an Attention Enhancer: Reviewing Existing Assumptions
Einöther, S. J. L., & Giesbrecht, T. (2013) · Psychopharmacology · doi:10.1007/s00213-012-2917-4 · Cited by 215
Green tea effects on cognition, mood and human brain function: A systematic review
Mancini, E., Beglinger, C., Drewe, J., Zanchi, D., Lang, U. E., & Borgwardt, S. (2017) · Phytomedicine · doi:10.1016/j.phymed.2017.07.008 · Cited by 229
“L-Theanine Ten experimental studies (Einother et al., 2010; Giesbrecht et al., 2010; Haskell et al., 2008; Kelly et al., 2008; Kimura et al., 2007; Ota et al., 2014; Owen et al., 2008; Park et al., 2011; Ritsner et al., 2011; Yoto et al., 2012) focussed on the effects of L-theanine intake.”
BackgroundResultInfluential
Metadata
- Authors
- Kelly, S. P., Gomez-Ramirez, M., Montesi, J. L., & Foxe, J. J.
- Affiliations
- Nathan Kline Institute for Psychiatric Research (US)
- Corresponding author
- Foxe, John J.
- Venue
- The Journal of Nutrition
- Publisher
- Elsevier BV
- Published
- 2008-08
- Volume
- 138
- Issue
- 8
- Pages
- 1572S-1577S
- ISSN
- 0022-3166 (ISSN-L)
- OpenAlex
- W1955323883
- Semantic Scholar
- e5aa9a2bad9f3c3193ccf2cfe466cfbff42c9594
- Cited by
- 119
- References
- 44
- Citations by year
- 2026: 5 · 2025: 5 · 2024: 4 · 2023: 4 · 2022: 5 · 2021: 7 · 2020: 5 · 2019: 5 · 2018: 4 · 2017: 9 · 2016: 10 · 2015: 2 · 2014: 10 · 2013: 6 · 2012: 3
- FWCI
- 7.82
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Licence
- Locations
- Journal of Nutrition (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Health Sciences › Medicine › Pharmacology (medical) › Coffee research and impacts
- Life Sciences › Neuroscience › Cognitive Neuroscience › Neural dynamics and brain function
- Social Sciences › Psychology › Experimental and Cognitive Psychology › Sleep and Work-Related Fatigue
- Keywords
- theanine, caffeine, tea constituents, visuospatial attention, alpha activity, anticipatory attention, attentional deployment, combination supplementation, cognitive performance
- MeSH terms
- Adult, Central Nervous System Stimulants, Attention, Brain Mapping, Caffeine, Cognition, Cues, Drug Therapy, Combination, Electroencephalography, Female, Glutamates, Humans, Male, Task Performance and Analysis
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
A language model drew the claims from the paper on 2026-10-05, under version 3 of the claim definition (model deepseek-v4.1-flash, prompt extract-v3).
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Cited sources are checked with a language model’s help (gpt-6-sol).
Statistics and arithmetic are recomputed, not judged.
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