Theanine Supplement Ingredient

Impact

High effect

Typical dose:100–400 mg

Found in green tea, L-Theanine is an amino acid that modulates neurotransmitters like GABA and dopamine. It is highly effective at taking the 'edge' off stimulants like caffeine, resulting in smooth, focused energy and reduced anxiety.

Study evidence

25 studies

Theanine can improve some short-term measures of attention, but its effects are task-dependent and do not consistently extend to broader cognition. Benefits seen with caffeine combinations cannot be assigned to theanine alone, and some trials report no benefit or poorer performance.

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Mental Focus

Impact

High effect

Typical dose:100–400 mg

Found primarily in green tea, L-Theanine modulates neurotransmitters like dopamine and GABA. It provides a non-drowsy relaxation effect that can mitigate the jitteriness of caffeine, leading to a synergistic improvement in smooth, sustained mental focus.

Study evidence

19 studies

Theanine may modestly improve selected attention tasks, but effects on mental focus are inconsistent. Benefits seen with caffeine cannot be attributed to theanine alone, and the available research does not establish a reliable improvement in sustained concentration or everyday performance.

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Productivity Boost

Impact

High effect

Typical dose:100–400 mg

L-Theanine is an amino acid that can cross the blood-brain barrier and increase alpha brain wave activity, which is associated with a state of 'relaxed wakefulness'. It can modulate neurotransmitters like GABA and dopamine, improving focus and attention without sedation.

Study evidence

5 studies

Theanine may modestly improve attention on certain laboratory tasks, but this has not established better everyday productivity. Findings vary across tests, fatigue relief is not supported by pooled evidence, and stress-related improvements are less consistent than attention effects.

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Sleep Support

Impact

High effect

Typical dose:100–400 mg

L-theanine has been investigated in small human studies of stress and sleep. Some sleep measures improved, while results differed across studies and populations. Benefits for anxiety or insomnia and the risk of next-day drowsiness remain uncertain.

Study evidence

8 studies

Theanine may modestly improve perceived sleep quality and some sleep-related difficulties, but results are inconsistent. Evidence is stronger for selected self-reported outcomes than for reliably treating insomnia, and research combining theanine with other ingredients limits conclusions about theanine alone.

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Stress Relief

Impact

High effect

Typical dose:100–400 mg

This amino acid, commonly found in green tea, can cross the blood-brain barrier and influence neurotransmitter levels. It enhances GABA, serotonin, and dopamine, leading to a quick-acting reduction in mental and physical stress while improving focus.

Study evidence

16 studies

Theanine may reduce some immediate stress responses and feelings of tension, especially during stressful tasks. Evidence for sustained everyday Stress Relief is less certain, and trials have not consistently shown better mood or anxiety outcomes than placebo, including in generalized anxiety disorder.

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Brain Health

Impact

Moderate effect

Typical dose:100–200 mg

This amino acid, commonly found in green tea, induces a state of wakeful relaxation without causing drowsiness. It is particularly effective at smoothing out the 'jitters' from caffeine while synergistically enhancing its positive effects on focus and attention.

Study evidence

17 studies

Theanine may improve selected attention tasks and support a calmer response to stress, but cognitive results are not uniform. The available human evidence concerns performance and mood measures rather than lasting brain protection or prevention of cognitive decline.

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