ハーブ臨床用量 · 100–200mg for cognitive enhancement効果発現時間 · 15–45 minutes (acute)

Caffeine

Name: Caffeine — Human Clinical Effect Matrix
Creator: The Nootropic Lab
License: https://creativecommons.org/licenses/by/4.0/

Caffeine is one of the most extensively studied psychoactive compounds. A 2016 review (McLellan, Caldwell & Lieberman — a narrative review, not a meta-analysis) found low-to-moderate doses (~40–300mg) consistently improve alertness, vigilance, attention and reaction time, with less consistent effects on memory and executive function. A 2010 Cochrane review of shift workers and a 2026 meta-analysis of 7 military sleep-loss RCTs confirmed gains in attention, vigilance and complex task performance. Side effects rise with dose, and the European Food Safety Authority (EFSA, 2015) sets 200mg per single dose and 400mg/day as safe for healthy adults — 200mg/day for pregnant women.

By The Nootropic Lab editorial teamUpdated 2026年10月9日8 min read✓ Fact-checked

エビデンス確認日: 2026年9月28日

作用機序

Caffeine is an adenosine receptor antagonist. By blocking adenosine (the neurotransmitter responsible for drowsiness), caffeine increases dopamine, norepinephrine, and acetylcholine signalling — producing wakefulness, elevated mood, and enhanced focus. It also increases cyclic AMP levels, which amplify downstream catecholamine effects.

臨床エビデンスの概要

ヒト効果マトリクス

Based on human clinical trials only. Animal and in-vitro data excluded.

効果	エビデンス	効果の大きさ	研究数	備考
Alertness & Wakefulness	strong	大	2	Most robust effect of caffeine: consistent after low-to-moderate doses (McLellan 2016); vigilance/response performance SMD 0.73 during sleep loss (2026 military meta-analysis).
Reaction Time	strong	中	3	Improved orientation/attention in the Cochrane shift-worker review and consistent response-time gains during sleep loss; one of the more tolerance-resistant effects.
Sustained Attention	strong	中	2	Particularly effective during sleep deprivation or extended work sessions (complex cognitive performance SMD 0.54 in the 2026 military meta-analysis).
Memory Consolidation	moderate	小	1	Post-study caffeine enhanced 24-hour memory consolidation (not retrieval), with an inverted-U dose-response (Borota 2014). Effect modest compared to attention benefits.

Evidence key: Strong = multiple consistent RCTs · Moderate = smaller/fewer RCTs · Preliminary = early trials or small n · Mixed = conflicting results

実証された効果

Increased alertness
Faster reaction time
Sustained attention during sleep loss
Improved physical performance above ~200mg

副作用と注意事項

Pregnancy: EFSA advises limiting habitual intake to 200mg/day from all sources
Panic disorder: in a meta-analysis, 53.9% of people with panic disorder had a panic attack after high-dose caffeine (~400–750mg) versus 1.7% of healthy controls — avoid or keep doses low
Headache, abdominal discomfort, rapid heart rate, insomnia and anxiety rise with dose, especially above ~6mg/kg (~420mg for a 70kg adult)
Insomnia: 400mg taken even 6 hours before bedtime reduced total sleep time
Tolerance development
Withdrawal headaches

摂取方法

Dosage100–200mg for cognitive effects; do not exceed 400mg/day (EFSA: up to 200mg per single dose; 200mg/day in pregnancy)

TimingMorning or early afternoon. Avoid within 8 hours of bedtime — a 400mg dose disrupted sleep even when taken 6 hours before bed.

With foodCan be taken with or without food. Food slows absorption slightly, reducing peak intensity but extending duration.

CyclingOptional: some people take a week off every 8–12 weeks to reduce tolerance; this has not been tested in trials.

FormsCoffee, tea, matcha, capsules, or anhydrous powder. Capsules provide the most precise dosing. Matcha provides a gentler curve due to L-Theanine co-occurrence.

スタッキングの推奨

Caffeineと相性の良い成分とその理由。

L-Theanine

The most studied nootropic stack. Trials used roughly 1:1 to 1.7:1 theanine:caffeine and found better attention than caffeine alone; in a controlled trial theanine did not significantly reduce jitteriness. Found naturally in matcha.

L-Tyrosine

Caffeine depletes dopamine precursors over time. L-Tyrosine replenishes substrate, reducing the crash and maintaining sustained focus.

Rhodiola Rosea

Rhodiola provides stress resilience while caffeine provides stimulation — complementary under high-demand conditions without overstimulation.

よくある質問

How much caffeine is too much?

EFSA (2015) concluded that single doses up to 200mg and daily intake up to 400mg do not raise safety concerns for healthy adults, and that pregnant women should stay at or below 200mg/day. People with panic disorder are far more likely to have a panic attack after high doses. Above these levels, anxiety, heart palpitations, and sleep disruption become common. For cognitive enhancement, 100-200mg is the sweet spot — higher doses provide diminishing returns for cognition while increasing side effects.

Does caffeine tolerance reduce its cognitive benefits?

Partially. Tolerance develops quickly to subjective alertness (the "I feel awake" feeling) but more slowly to objective cognitive benefits like reaction time and vigilance. Even habitual consumers show faster reaction times after caffeine vs. placebo. However, taking periodic breaks (1-2 weeks) can partially reset tolerance.

Is caffeine from coffee different from caffeine in supplements?

Chemically, caffeine is caffeine regardless of source. However, coffee contains chlorogenic acids and other polyphenols that may modulate absorption kinetics and provide independent neuroprotective effects. Supplement caffeine (anhydrous) hits faster and harder. Neither is objectively better — it depends on whether you want precision dosing (capsule) or a gentler curve (coffee/tea).

Can I take caffeine with nootropic stacks that contain stimulants?

Be careful. Many nootropic stacks (e.g. Hunter Focus) already contain 100mg caffeine. Adding coffee or caffeine pills on top can push you over 400mg/day. Always check the label for caffeine content before stacking. If a product contains caffeine, reduce your external caffeine intake accordingly.

Top stacks containing Caffeine

Hunter Focus

7.7/10

Roar Ambition

Caffeine in Japan

Products in Japan

Hunter Focus7.7/10
No FFC notification found (checked 2026-10-06)Local price: ￥13,500/month

Consumer Affairs Agency (FFC)

Prefecture guides

Regulatory note

本ページは教育目的の編集コンテンツであり、医学的助言を構成するものではありません。日本国内で販売される機能性表示食品（FFC）および特定保健用食品（FOSHU）は、消費者庁への届出または許可を必要とします。届出のない輸入品については、日本の薬機法（旧薬事法）の下で疾病治療を示唆する表現は規制されます。サプリメントを開始する前に、必ず資格のある医療専門家にご相談ください。This page is editorial and not medical advice. Foods with Function Claims (FFC) and Foods for Specified Health Uses (FOSHU) sold in Japan require notification or approval from the Consumer Affairs Agency. Imported products without notification cannot make disease-treatment claims under the Pharmaceuticals and Medical Devices (PMD) Act. Note: In July 2026, the Consumer Affairs Agency (CAA) opened a public comment period (Notice No. 235080088, closes 30 July 2026) on proposed revisions to permitted claim wording for FFC-notified ingredients including DHA, phosphatidylserine, and NMN; compliant claim language may require updating once the final Cabinet Office Order is published. Consult a qualified healthcare professional before starting any supplement.

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