Place · Level 3
Caffeine + L-Theanine
世界最普及精神物质 + 茶叶独有氨基酸 · 1:2 协同最有 RCT 证据的认知组合· 但个体差异极大
Last updated
Story path
- 1Caffeine · adenosine blockadeCaffeine · adenosine blockade
- 2L-Theanine · tea's signature aminoL-Theanine · tea's signature amino
- 31:2 synergy · classic RCTs1:2 synergy · classic RCTs
- 4CYP1A2 genetics · individual variationCYP1A2 genetics · individual variation
- 5Use cases · study / work / sportUse cases · study / work / sport
Chapter 1
Caffeine · adenosine blockade
Caffeine · adenosine blockade
The plain version first: caffeine doesn't 'inject energy' — it temporarily blocks the brain's 'time to sleep' signal, so the tiredness is still there, you just stop feeling it for a while. That makes it more like releasing a brake than hitting the gas. Below: how it blocks that signal, and why the same cup leaves some people fine and others jittery.
Caffeine (1,3,7-trimethylxanthine) is the most widely used psychoactive substance on the planet — roughly 80% of adults worldwide consume it daily.
Mechanism · the adenosine impostor:
Adenosine is the body's endogenous *sleep-pressure molecule* — it accumulates during waking hours, binds brain A1 + A2A receptors, and slows neural activity while building drowsiness.Caffeine is structurally similar to adenosine → it competitively binds A1/A2A without activating them → "fakes blocking the door".Result: the "you're tired" signal is masked → alertness, vigilance, and attention rise.Caffeine is not injecting energy — it is masking the fatigue signal.
Pharmacokinetics:
Oral → plasma peak in 30-60 minHalf-life 5-7 h (large individual variation, see below)Full metabolism 8-12 h
Main metabolic pathway · CYP1A2 (liver):
Handles ~95% of caffeine clearanceCYP1A2 polymorphism splits the population into *fast* vs *slow* metabolizers:Fast (~60% of Asians, ~50% of Westerners): half-life ~4-5 h, mild cardiovascular response, "doesn't affect my sleep".Slow (~15%): half-life ~8-12 h, more sensitive at the same dose. Cornelis 2006 *JAMA* showed slow metabolizers with high caffeine intake had MI risk ↑36%.23andMe and similar consumer tests actually return CYP1A2 — it is real, actionable data.
Other effects on the body:
Dopamine + norepinephrine: indirectly released via adenosine blockade → mood liftβ-adrenergic receptors: brief rise in HR and BP (harmless in healthy people)Basal metabolism: short-term ↑ ~5-10% (the weight-loss supplement selling point — but small)Cognition: attention, reaction time, and simple-task performance ↑; complex-task effects are weaker
"Caffeine isn't really a stimulant": strictly speaking caffeine is a disinhibitor — it doesn't directly excite the brain, it removes a brake (adenosine). True stimulants like amphetamine and methylphenidate directly release dopamine — stronger effect, but also higher risk.
Caffeine (1,3,7-trimethylxanthine) is the most widely used psychoactive substance on the planet — roughly 80% of adults worldwide consume it daily.
Mechanism · the adenosine impostor:
Adenosine is the body's endogenous *sleep-pressure molecule* — it accumulates during waking hours, binds brain A1 + A2A receptors, and slows neural activity while building drowsiness.Caffeine is structurally similar to adenosine → it competitively binds A1/A2A without activating them → "fakes blocking the door".Result: the "you're tired" signal is masked → alertness, vigilance, and attention rise.Caffeine is not injecting energy — it is masking the fatigue signal.
Pharmacokinetics:
Oral → plasma peak in 30-60 minHalf-life 5-7 h (large individual variation, see below)Full metabolism 8-12 h
Main metabolic pathway · CYP1A2 (liver):
Handles ~95% of caffeine clearanceCYP1A2 polymorphism splits the population into *fast* vs *slow* metabolizers:Fast (~60% of Asians, ~50% of Westerners): half-life ~4-5 h, mild cardiovascular response, "doesn't affect my sleep".Slow (~15%): half-life ~8-12 h, more sensitive at the same dose. Cornelis 2006 *JAMA* showed slow metabolizers with high caffeine intake had MI risk ↑36%.23andMe and similar consumer tests actually return CYP1A2 — it is real, actionable data.
Other effects on the body:
Dopamine + norepinephrine: indirectly released via adenosine blockade → mood liftβ-adrenergic receptors: brief rise in HR and BP (harmless in healthy people)Basal metabolism: short-term ↑ ~5-10% (the weight-loss supplement selling point — but small)Cognition: attention, reaction time, and simple-task performance ↑; complex-task effects are weaker
"Caffeine isn't really a stimulant": strictly speaking caffeine is a disinhibitor — it doesn't directly excite the brain, it removes a brake (adenosine). True stimulants like amphetamine and methylphenidate directly release dopamine — stronger effect, but also higher risk.
它在体内待多久 · 拆它的那把酶 · 它到底算不算兴奋剂
上面讲的是它怎么堵, 这一页讲堵多久——同样一杯咖啡在两个人身体里停留的时间可以差出一倍, 而那个差别不在杯子里, 在肝脏里。几个时间数字: 口服后 30-60 分钟血浆达到峰值, 半衰期 5-7 小时 (个体差异很大, 见下), 完全代谢掉要 8-12 小时。
半衰期指的是血里的咖啡因掉到一半所需要的时间, 不是药效结束的时间。所以一杯下午喝的咖啡, 到你躺下时血里往往还留着可观的一部分; 你可能主观上早就感觉不到它了, 但那部分仍然坐在腺苷的接收口上, 深睡因此被压掉一截。感觉不到和没作用是两件事。
主要代谢通路: CYP1A2 (肝):
占 ~ 95% 咖啡因清除CYP1A2 基因多态性: 快代谢者vs慢代谢者快代谢者 (~ 60% 亚洲人 + 50% 西方人): 半衰期 ~ 4-5 小时, 喝咖啡心血管反应温和, 不影响睡眠慢代谢者 (~ 15%): 半衰期 ~ 8-12 小时, 同样剂量更敏感; Cornelis 2006 JAMA 显示慢代谢者高咖啡因摄入与心梗风险 ↑ 36%23andMe 等测的 CYP1A2 是真实可执行的基因数据
CYP1A2 是肝细胞里的一种酶, 它的活儿就是把咖啡因这类分子剪开、贴上水溶性的标签, 好让肾脏把它冲进尿里。同一把剪刀, 有人天生产得多、剪得快, 有人产得少、剪得慢——这就是上面那张表里快和慢的物理含义。本岛的第四幕专讲这件事。
身体其它效应:
多巴胺 + 去甲肾上腺素: 通过腺苷阻断间接释放 → 心情提升, 情绪改善β-肾上腺受体: 心率 + 血压短暂升 (健康人无害)基础代谢: 短期升 ~ 5-10% (减肥补剂卖点, 但小)认知: 注意力、反应速度、简单任务表现 ↑; 复杂任务效应弱
咖啡因不是兴奋剂: 严格说咖啡因是抗抑制剂 (disinhibitor) —— 它不直接刺激大脑, 而是移除一个刹车(腺苷)。真正的兴奋剂如安非他命、哌甲酯直接释放多巴胺, 作用更强 + 风险更高。
这个区别有实际后果: 移除刹车的东西, 效果上限被你本来还剩多少精力卡死——你越累, 腺苷攒得越多, 同一杯咖啡能挡住的比例就越小。所以熬到第三天再灌咖啡几乎没用, 而这不是耐受, 是刹车已经踩到底了。
Adenosine rebound + tolerance + withdrawal
Why people who drink coffee daily feel awful without it:1. Receptor upregulation:
Long-term blockade of A1/A2A → the body compensates by increasing receptor numbers.Once you stop, adenosine can now bind more receptors → drowsiness exceeds the original baseline.That is why people quitting coffee feel abnormally tired in the first 2-4 days.
2. Classic caffeine withdrawal symptoms (~50% of long-term users):
Headache (rebound cerebral vasodilation, usually peaks day 2-3)Extreme fatigueLow mood / irritability / anxietyPoor focusFlu-like symptoms (muscle aches, rare)Duration: usually 2-9 days, individual variation is large
Withdrawal vs true dependence:
The APA DSM-5 lists caffeine withdrawal as a formal diagnosis (294.81)."Caffeine use disorder" is still a research category, not a formal diagnosis.Unlike alcohol or opioids — caffeine does not cause withdrawal seizures or life-threatening reactions.
3. Tolerance:
After 2-3 weeks of continuous 200+ mg/day, the subjective effect of the same dose diminishes.Objective alertness may still rise — but the upregulated receptors have sunk the baseline, so caffeine just pulls you back to "normal"."I need coffee to feel normal" is a tolerance signal, not "my body needs it".
4. Cycling / caffeine holidays:
Take a 3-5 day break every 4-8 weeks — lets receptors return toward baseline.The first few days are uncomfortable, but the effect upon re-introduction is stronger.Athletes and performers use a "pre-competition stop" to amplify the day-of effect.Daily intake without breaks → permanent upregulation → "the effect is gone".
5. Individual variation:
CYP1A2 slow metabolizers (rs762551 AA genotype):Long half-life → an afternoon cup still disturbs deep sleepLarger cardiovascular response → palpitations and anxiety are commonMove the cutoff earlier (e.g. before noon)CYP1A2 fast metabolizers (CC genotype):Short half-life → "I can drink it in the evening and still sleep"But deep sleep quality may still suffer — subjective ≠ objective
Best practices:
1. Cutoff at 2 pm (most people)
2. CYP1A2 slow metabolizers: before noon
3. No more than 400 mg/day (~4 drip cups / 3 espressos / 10 cups of green tea)
4. Pregnancy: < 200 mg/day (ACOG)
5. Children and adolescents: 12-18 yo < 100 mg/day (AAP)
6. For sustained high effectiveness: take periodic breaks
Chapter 2
L-Theanine · tea's signature amino
L-Theanine · tea's signature amino
L-Theanine is a **non-protein amino acid almost exclusive to tea (*Camellia sinensis*)** — this is the biochemical reason "tea feels different from coffee".
Structure and sources:
Structure: γ-glutamylethylamide — chemically similar to both glutamate (Glu) and GABASource: 1-2% of dry weight in tea leavesGreen tea: ~10-20 mg per cup (200 mL)Black tea: ~5-15 mg/cupMatcha: ~20-40 mg per teaspoonWhite tea: highest, ~25-40 mg/cupDark / pu-erh: lowerTrace amounts exist in certain mushrooms, but tea is the only commercial source.
Entry into the brain:
Crosses the blood-brain barrier via the LAT1 transporterPlasma peak: 30-60 min after oral doseHalf-life: ~60-75 minNo toxicity on record (RCTs tolerate 1200 mg/day well)
Mechanism (four layers):
① GABAergic modulation:
Does not directly bind the GABA-A receptor (unlike benzodiazepines)May indirectly raise brain GABA (Nathan 2006 review) → reduced anxiety signalling. Note this layer is the weakest-evidenced of the fourThis is the chemical basis for "relaxed but not drowsy"
② Glutamate modulation:
Antagonizes NMDA receptors → reduces over-excitationCounterbalances caffeine's over-activation
③ Dopamine + serotonin:
Mild elevation of both → mood lift
④ Alpha brain waves:
8-13 Hz alpha = the "relaxed but alert" brain state (dominant during meditation and deep focus)L-theanine directly increases α-wave amplitude (*Nobre 2008* and *Kelly 2008*)This is the objective physiological signature of the "relaxed focus" feeling
Why tea feels different from coffee:
Caffeine in tea: 50-70 mg per cup (vs 80-150 mg in coffee)Plus 10-20 mg of L-theanineApproximate 4:1 caffeine-to-theanine ratioResult: gentle alertness, no anxiety, longer-lastingDistinctly different from pure caffeine — "tea people" vs "coffee people" report different experiences not because of culture, but because of chemistry.
Matcha vs green tea:
Matcha is whole-leaf ground and consumed, so L-theanine content is 3-5× higher than steeped green teaAlso contains more chlorophyll and EGCGBut caffeine is also higher — so the net ratio is similar to steeped green tea
Structure and sources:
Structure: γ-glutamylethylamide — chemically similar to both glutamate (Glu) and GABASource: 1-2% of dry weight in tea leavesGreen tea: ~10-20 mg per cup (200 mL)Black tea: ~5-15 mg/cupMatcha: ~20-40 mg per teaspoonWhite tea: highest, ~25-40 mg/cupDark / pu-erh: lowerTrace amounts exist in certain mushrooms, but tea is the only commercial source.
Entry into the brain:
Crosses the blood-brain barrier via the LAT1 transporterPlasma peak: 30-60 min after oral doseHalf-life: ~60-75 minNo toxicity on record (RCTs tolerate 1200 mg/day well)
Mechanism (four layers):
① GABAergic modulation:
Does not directly bind the GABA-A receptor (unlike benzodiazepines)May indirectly raise brain GABA (Nathan 2006 review) → reduced anxiety signalling. Note this layer is the weakest-evidenced of the fourThis is the chemical basis for "relaxed but not drowsy"
② Glutamate modulation:
Antagonizes NMDA receptors → reduces over-excitationCounterbalances caffeine's over-activation
③ Dopamine + serotonin:
Mild elevation of both → mood lift
④ Alpha brain waves:
8-13 Hz alpha = the "relaxed but alert" brain state (dominant during meditation and deep focus)L-theanine directly increases α-wave amplitude (*Nobre 2008* and *Kelly 2008*)This is the objective physiological signature of the "relaxed focus" feeling
Why tea feels different from coffee:
Caffeine in tea: 50-70 mg per cup (vs 80-150 mg in coffee)Plus 10-20 mg of L-theanineApproximate 4:1 caffeine-to-theanine ratioResult: gentle alertness, no anxiety, longer-lastingDistinctly different from pure caffeine — "tea people" vs "coffee people" report different experiences not because of culture, but because of chemistry.
Matcha vs green tea:
Matcha is whole-leaf ground and consumed, so L-theanine content is 3-5× higher than steeped green teaAlso contains more chlorophyll and EGCGBut caffeine is also higher — so the net ratio is similar to steeped green tea
含量 · 入脑 · 四条通路
L-茶氨酸 (L-Theanine) 是茶叶 (Camellia sinensis) 几乎独有的非蛋白氨基酸——这是为什么喝茶感觉与喝咖啡不同的生化原因:化学结构 + 来源:
结构: γ-glutamylethylamide —— 与谷氨酸 (Glu) 和 GABA 都化学相似来源: 茶叶 1-2% 干重绿茶: ~ 10-20 mg / 杯 (200 mL)红茶: ~ 5-15 mg / 杯抹茶: ~ 20-40 mg / 茶匙白茶: 含量最高 ~ 25-40 mg / 杯黑茶、普洱: 较低极少量也在某些菌菇里, 但茶叶是唯一商业来源
进入大脑:
过血脑屏障: 是, 通过 LAT1 转运体血浆峰值: 口服 30-60 分钟后半衰期: ~ 60-75 分钟无毒性记录 (RCT 高剂量 1200 mg/天耐受良好)
LAT1 这个细节值得多说一句: 血脑屏障不是一堵挡住所有东西的墙, 而是一排各管一类分子的闸门。LAT1 是专门往脑内搬运大个头氨基酸的那道闸门, 茶氨酸长得像氨基酸, 于是搭上了这班车。这也解释了它为什么起效并不慢——不用等代谢, 直接被搬进去。
机制 (4 个层面):
① GABA-能调节:
不直接结合 GABA-A 受体 (与苯二氮卓不同)可能间接升脑内 GABA (Nathan 2006 综述) → 减少焦虑信号。四层机制里这一层的证据最弱这是放松不嗜睡的化学基础
② 谷氨酸调节:
拮抗 NMDA 受体 → 减少过度兴奋平衡了咖啡因的过度激活
③ 多巴胺 + 血清素:
轻度升高两者 → 心情提升
④ Alpha 脑电波:
8-13 Hz α 波 = 放松但警觉的脑状态 (冥想 + 深度专注时主导)L-theanine 直接增加 α 波幅度 (Nobre 2008 + Kelly 2008)这是放松专注感觉的客观生理标志
第一条和第二条的差别是这一节的重点。苯二氮卓类镇静药是直接坐上 GABA 受体、把那个闸门掰得更开, 所以它的量一大人就倒下去; 茶氨酸只是让 GABA 这个信号本身多一点, 受体开多大仍由身体自己定。放松而不嗜睡这句话的物理含义就在这里——它抬的是信号, 不是开关。
为什么喝茶感觉与咖啡不同:
茶里咖啡因 = 50-70 mg / 杯 (vs 咖啡 80-150 mg)加上 L-theanine 10-20 mg比例约 4:1 咖啡因 / theanine结果: 温和提神 + 不焦虑 + 持续时间长与纯咖啡因感觉很不同——这就是为什么茶人与咖啡人常说体验不同, 不是文化, 是化学
抹茶 vs 绿茶:
抹茶整叶磨粉喝下 → L-theanine 含量比泡的绿茶高 3-5 倍也含叶绿素 + 儿茶素 EGCG 更多但咖啡因也更高 —— 净比例和泡绿茶类似
Tea vs coffee preference — chemistry
Why do some people get anxious on coffee but not on tea?Main variables:
1. Absolute caffeine amount:
A drip coffee: ~95-150 mgAn espresso: ~60-80 mgA cup of green tea: ~30-50 mgFor a novice or slow metabolizer, the felt difference between 50 mg and 150 mg is huge
2. Co-administration of L-theanine:
Tea has a natural ~1:4 ratio → alertness + relaxationCoffee has 0 mg L-theanine → pure activation
3. Speed of intake:
Tea is usually sipped slowly (hot, 10-30 min/cup)Coffee is often drunk quickly (1-2 cups in a short window)The same total caffeine feels very different sustained vs concentrated
4. Polyphenols and antioxidants:
Tea contains EGCG + catechins → mild anti-inflammatory + antioxidantCoffee contains chlorogenic acid → also antioxidant, but a different set of compounds
5. Stomach and GI:
Coffee stimulates gastric acid + relaxes the lower esophageal sphincter → reflux is more commonTea is comparatively gentleThis is why many people report "coffee stomach" but not "tea stomach"
Practical recommendations:
Afternoon alertness without anxiety: matcha / strong tea / green tea — built-in L-theanine balances the caffeineFast short-term focus: a single espresso, 50-80 mgWant to keep some caffeine without overload: light roast or cold brew + one cup of tea, balancedSevere coffee-induced anxiety: switch to pure green / white tea, or chamomile / fennel; go fully caffeine-free for 2 weeks and re-assess
"Is coffee or tea better" is not a single answer — it depends on:
Your CYP1A2 genotypeYour anxiety / sleep baselineYour goal (short focus vs sustained work vs social situation)Your gut tolerance
So "coffee vs tea" is not the question of "which is healthier" — it is the question of "which suits you".
Chapter 3
1:2 synergy · classic RCTs
1:2 synergy · classic RCTs
Caffeine + L-theanine is one of the few supplement combinations with RCT-supported synergy:
Owen 2008 *Nutritional Neuroscience* RCT:
N = 27 healthy young adultsCaffeine 50 mg + L-theanine 100 mg vs caffeine alone vs theanine alone vs placeboTasks: attention switching, vigilance, visual trackingResult: the combination group significantly outperformed any individual arm on multiple cognitive tasksSignature: attention + accuracy ↑ without caffeine's standalone "subjective anxiety"
Kelly 2008 *J Nutrition*:
N = 27 adults, crossover designCaffeine 50 mg + L-theanine 100 mg with EEG + behavioral testingResults:Alpha brain wave (relaxed focus) ↑Attention-switching error rate ↓ 13%Reaction-time consistency ↑
Follow-up work — Haskell 2008, Giesbrecht 2010, and others:
Multiple small RCTs reproduce the effect — stableMost commonly used ratio: caffeine : L-theanine = 1 : 2 (e.g. 50 + 100 mg, or 100 + 200 mg)
Why 1:2?
Tea's natural ratio is ~1:4 (caffeine:theanine) — leans toward relaxationRCTs show 1:2 is best for cognitive performance — meaningful caffeine effect with L-theanine smoothing the anxiety1:3 leans relaxation (good for anxious users); 1:1 leans activation
Typical dosing protocols:
Light alertness + work flow: caffeine 50 mg + L-theanine 100 mg (≈ one strong cup of tea + a 100 mg theanine capsule)Strong alertness without anxiety: caffeine 100 mg + L-theanine 200 mg (≈ one drip coffee + 200 mg cap)Studying / exams: same as above, taken with a mealSport performance: caffeine 200 mg + L-theanine 100 mg (activation-leaning)
Onset and duration:
Peak at 30-60 minEffect lasts 3-5 hSofter landing than caffeine alone
Natural source vs standalone supplement:
Green tea / matcha: provide the natural combo, but L-theanine dose is too small (15-40 mg) → synergy is weakGreen tea + a separate L-theanine capsule: lets you push the theanine ratio up flexiblyCoffee + 100-200 mg L-theanine capsule: balances coffee-induced anxiety; multiple supplement brands sell this combination (Now, Sports Research, NooCube, etc.)"Green tea extract supplements": often highly concentrated EGCG + caffeine → very different from drinking tea, with hepatotoxicity reports (covered in the ashwagandha story)
Real-world markers of "it's working":
Subjective: "alert but not anxious", "focused but not tight"Objective (if you have the equipment): EEG α-wave amplitude ↑, attention-switching accuracy ↑
Owen 2008 *Nutritional Neuroscience* RCT:
N = 27 healthy young adultsCaffeine 50 mg + L-theanine 100 mg vs caffeine alone vs theanine alone vs placeboTasks: attention switching, vigilance, visual trackingResult: the combination group significantly outperformed any individual arm on multiple cognitive tasksSignature: attention + accuracy ↑ without caffeine's standalone "subjective anxiety"
Kelly 2008 *J Nutrition*:
N = 27 adults, crossover designCaffeine 50 mg + L-theanine 100 mg with EEG + behavioral testingResults:Alpha brain wave (relaxed focus) ↑Attention-switching error rate ↓ 13%Reaction-time consistency ↑
Follow-up work — Haskell 2008, Giesbrecht 2010, and others:
Multiple small RCTs reproduce the effect — stableMost commonly used ratio: caffeine : L-theanine = 1 : 2 (e.g. 50 + 100 mg, or 100 + 200 mg)
Why 1:2?
Tea's natural ratio is ~1:4 (caffeine:theanine) — leans toward relaxationRCTs show 1:2 is best for cognitive performance — meaningful caffeine effect with L-theanine smoothing the anxiety1:3 leans relaxation (good for anxious users); 1:1 leans activation
Typical dosing protocols:
Light alertness + work flow: caffeine 50 mg + L-theanine 100 mg (≈ one strong cup of tea + a 100 mg theanine capsule)Strong alertness without anxiety: caffeine 100 mg + L-theanine 200 mg (≈ one drip coffee + 200 mg cap)Studying / exams: same as above, taken with a mealSport performance: caffeine 200 mg + L-theanine 100 mg (activation-leaning)
Onset and duration:
Peak at 30-60 minEffect lasts 3-5 hSofter landing than caffeine alone
Natural source vs standalone supplement:
Green tea / matcha: provide the natural combo, but L-theanine dose is too small (15-40 mg) → synergy is weakGreen tea + a separate L-theanine capsule: lets you push the theanine ratio up flexiblyCoffee + 100-200 mg L-theanine capsule: balances coffee-induced anxiety; multiple supplement brands sell this combination (Now, Sports Research, NooCube, etc.)"Green tea extract supplements": often highly concentrated EGCG + caffeine → very different from drinking tea, with hepatotoxicity reports (covered in the ashwagandha story)
Real-world markers of "it's working":
Subjective: "alert but not anxious", "focused but not tight"Objective (if you have the equipment): EEG α-wave amplitude ↑, attention-switching accuracy ↑
原始试验 · 比例怎么定 · 剂量方案
把上面那句有 RCT 支持拆开, 具体是这几项:Owen 2008 (Nutritional Neuroscience) RCT:
N=27 健康年轻成人咖啡因 50 mg + L-theanine 100 mg vs 单独咖啡因 vs 单独 theanine vs 安慰剂任务: 注意切换、警觉、视觉追踪结果: 组合组在多个认知任务上显著优于单独任一特征: 注意力 + 准确性 ↑, 但不带 caffeine 单独的主观焦虑
注意这个设计: 它有四条臂, 不是吃 vs 不吃两条。只有把单独咖啡因、单独茶氨酸也各测一遍, 组合优于其中任何一个这句话才成立——否则你分不清收益是来自组合, 还是来自里面某一样单打独斗。这也是协同这个词在这里能站住脚的原因。
Kelly 2008 (J Nutrition):
N=27 成人, 交叉设计咖啡因 50 mg + L-theanine 100 mg EEG + 行为测试结果:Alpha 脑电波 (放松专注) ↑注意切换错误率 ↓ 13%反应时一致性 ↑
Haskell 2008 + Giesbrecht 2010 等后续:
多个小型 RCT 复现, 效应稳定常用的两档具体量: 50 mg + 100 mg, 或 100 mg + 200 mg
为什么 1:2?
茶叶自然比例约 1:4 (咖啡因:theanine) —— 偏向放松RCT 显示 1:2 在认知性能最佳 —— 仍有显著的咖啡因效用 + L-theanine 削平焦虑1:3 偏向放松 (适合焦虑者), 1:1 偏向激活
换句话说, 这个比例不是化学上的神圣数字, 是一个你想要多少清醒、能忍多少紧绷的滑块。茶叶天生那一档偏向放松, 是因为茶是拿来喝一下午的; 认知任务要的是短窗口内的表现, 所以试验把滑块往咖啡因那边挪了一格。
典型剂量方案:
轻度提神 + 工作流: caffeine 50 mg + L-theanine 100 mg (相当于 1 杯浓茶 + 一颗 100 mg 茶氨酸)强提神 + 不焦虑: caffeine 100 mg + L-theanine 200 mg (相当于 1 杯滴漏咖啡 + 200 mg theanine)学习、考试: 同上, 餐后服运动表现: caffeine 200 mg + L-theanine 100 mg (偏激活)
起效时间:
30-60 分钟达峰效应持续 3-5 小时比单独咖啡因降落更柔和
降落更柔和这条值得解释一下来源: 咖啡因掉下去的时候, 之前被它挡住的腺苷会一次性涌回接收口, 那种突然的疲惫就是所谓咖啡崩。茶氨酸不参与腺苷这条路, 但它把整个过程里的兴奋峰值削平了, 于是落差本身变小——不是让你掉得慢, 是让你本来就没被抛那么高。
自然来源 vs 单独补剂:
绿茶、抹茶: 提供天然组合, 但 L-theanine 量不够大 (15-40 mg) → 协同效应弱绿茶 + 单独 L-theanine 补片: 灵活提高 theanine 比例咖啡 + L-theanine 100-200 mg 胶囊: 平衡咖啡焦虑, 多个补剂厂卖此组合 (Now / Sports Research / NooCube 等)绿茶提取物补剂: 往往高度浓缩 EGCG + 含咖啡因 → 与喝茶不同, 有肝毒报告 (上次 ashwagandha 讲过)
实测有效标记:
主观: 清醒但不焦虑专注但不紧绷客观 (有条件): EEG α 波幅度 ↑, 注意切换准确率 ↑
Usage · timing · food effects
Best practices:1. Timing:
9-11 am: the natural cortisol drop — caffeine has its most pronounced effect here1-2 pm (post-lunch dip): a second dose; not later than 2 pmAvoid: the first 30 minutes after waking (the natural cortisol peak makes caffeine weak — wasted)Avoid: after 3 pm (with a 5-7 h half-life, this still interferes with 11 pm sleep)
2. Food:
On an empty stomach: fast onset, but gastric irritation + bigger adrenal responseWith food: onset 30 min slower, smoother + easier on the stomachL-theanine is food-independent
3. With other supplements / medications:
With iron: caffeine + tea catechins inhibit non-heme iron absorption by ~40-60% (per meta-analysis) — separate by 1-2 hWith antihypertensives / anticoagulants: caffeine briefly raises BP; anticoagulants may interact via CYP1A2 — confirm with your physicianWith SSRIs: theoretical 5-HT syndrome risk, but rare in practice
4. "Morning coffee + afternoon tea" template:
9 am: light roast coffee + 100 mg L-theanine capsule (high activation, smoothed anxiety) → morning deep work1 pm: matcha or strong tea (natural 1:4 ratio) → afternoon meetings without impacting sleep7 pm: herbal tea (chamomile / fennel / mint, caffeine-free) → start the night wind-down
5. Withdrawal or reduction plan:
If you're at > 400 mg caffeine/day with anxiety / insomnia / palpitations:Week 1: cut by 25%Week 2: cut another 25%Weeks 3-4: swap 50% for decaf or teaTarget: under 200 mg/dayAdd 200 mg L-theanine twice daily during the transition — eases anxiety rebound
6. Pregnancy / breastfeeding:
ACOG: caffeine < 200 mg/day (~1.5 drip cups)L-theanine: safety data are limited — conservative position: tea only, no isolated capsule
7. Diagnosed insomnia or anxiety:
Fully eliminate caffeine for 4 weeks and reassessMany people discover the real cause of their anxiety and insomnia was caffeine itself — not "I need a sleep aid"
Chapter 4
CYP1A2 genetics · individual variation
CYP1A2 genetics · individual variation
Caffeine's individual variation is one of the few areas in nutrition medicine with a clean genetic explanation:
CYP1A2 gene (chromosome 15):
rs762551 is the single-nucleotide polymorphism (SNP) that has been studied most thoroughlyAA genotype (~50% of Westerners, ~60% of Asians): fast metabolizers — high CYP1A2 expression, fast caffeine clearanceAC genotype (~40%): intermediateCC genotype (~10%): slow metabolizers — low CYP1A2 expression, slow caffeine clearance
Clinical difference (*Cornelis 2006* *JAMA*, N = 4,080 Costa Rica MI cohort):
Slow metabolizers (CC) drinking 4+ cups of coffee per day → MI risk ↑36% (vs non-drinkers)Fast metabolizers (AA) drinking 4+ cups per day → MI risk ↓22% (the opposite direction!)Intermediates (AC): risk close to non-drinkers
This is nutrition medicine's cleanest pharmacogenomics example — same dietary exposure, different genotype, reversed health outcomes.
Other manifestations of being a slow metabolizer:
Afternoon or evening coffee meaningfully affects sleepPalpitations and anxiety are more commonAcute BP response is large"I feel jittery after a coffee" → almost certainly the CC genotypeGestational hypertension risk also tracks with CYP1A2 slow + high caffeine intake
Fast metabolizers:
"I can drink coffee in the evening and still sleep" — usually genuinely trueSport performance effect of caffeine is smaller — higher doses are requiredSome studies suggest cardiovascular protection at moderate doses (but depends on dose and overall diet)
How to find out your genotype:
23andMe / AncestryDNA + Promethease / SNPedia: look up rs762551In China: WeGene / 微基因Genetic testing companies: ~$50-150Self-observation:"Does a 2 pm coffee affect my 11 pm sleep?" → likely slow"Do I feel jittery / anxious afterward?" → likely slow"Do I get more wired than friends or coworkers at the same dose?" → likely slowWatching yourself is the cheapest genotype probe there is
Practical adjustments:
Slow metabolizers:Cutoff: before 11 amDaily ceiling: 200 mg (~1.5 drip cups)Always pair with L-theanine: 200 mg to balance anxietyAvoid: high-caffeine energy / sports drinks, multiple espressosFast metabolizers:Cutoff: 2 pm (standard)Daily ceiling: 400 mgL-theanine: optional, personal preferenceSport: 200-400 mg pre-event is reasonable
CYP1A2 gene (chromosome 15):
rs762551 is the single-nucleotide polymorphism (SNP) that has been studied most thoroughlyAA genotype (~50% of Westerners, ~60% of Asians): fast metabolizers — high CYP1A2 expression, fast caffeine clearanceAC genotype (~40%): intermediateCC genotype (~10%): slow metabolizers — low CYP1A2 expression, slow caffeine clearance
Clinical difference (*Cornelis 2006* *JAMA*, N = 4,080 Costa Rica MI cohort):
Slow metabolizers (CC) drinking 4+ cups of coffee per day → MI risk ↑36% (vs non-drinkers)Fast metabolizers (AA) drinking 4+ cups per day → MI risk ↓22% (the opposite direction!)Intermediates (AC): risk close to non-drinkers
This is nutrition medicine's cleanest pharmacogenomics example — same dietary exposure, different genotype, reversed health outcomes.
Other manifestations of being a slow metabolizer:
Afternoon or evening coffee meaningfully affects sleepPalpitations and anxiety are more commonAcute BP response is large"I feel jittery after a coffee" → almost certainly the CC genotypeGestational hypertension risk also tracks with CYP1A2 slow + high caffeine intake
Fast metabolizers:
"I can drink coffee in the evening and still sleep" — usually genuinely trueSport performance effect of caffeine is smaller — higher doses are requiredSome studies suggest cardiovascular protection at moderate doses (but depends on dose and overall diet)
How to find out your genotype:
23andMe / AncestryDNA + Promethease / SNPedia: look up rs762551In China: WeGene / 微基因Genetic testing companies: ~$50-150Self-observation:"Does a 2 pm coffee affect my 11 pm sleep?" → likely slow"Do I feel jittery / anxious afterward?" → likely slow"Do I get more wired than friends or coworkers at the same dose?" → likely slowWatching yourself is the cheapest genotype probe there is
Practical adjustments:
Slow metabolizers:Cutoff: before 11 amDaily ceiling: 200 mg (~1.5 drip cups)Always pair with L-theanine: 200 mg to balance anxietyAvoid: high-caffeine energy / sports drinks, multiple espressosFast metabolizers:Cutoff: 2 pm (standard)Daily ceiling: 400 mgL-theanine: optional, personal preferenceSport: 200-400 mg pre-event is reasonable
rs762551 · 分布、心血管数据与两套方案
咖啡因的个体差异是营养医学里少数有清晰基因解释的:CYP1A2 基因 (染色体 15):
rs762551 单核苷酸多态性 (SNP) 是研究最透的位点AA 基因型 (~ 50% 西方人, 60% 亚洲人): 快代谢者 —— CYP1A2 表达高, 咖啡因清除快AC 基因型 (~ 40%): 中间型CC 基因型 (~ 10%): 慢代谢者 —— CYP1A2 表达低, 咖啡因清除慢
这里的表达高是字面意思: 同一个基因, 这个位点上的字母不同, 肝细胞照着它造出来的酶分子数量就不同。酶多, 单位时间剪开的咖啡因分子就多, 血里的浓度掉得快; 酶少, 同样一杯就在血里多待几个小时。所以代谢快慢不是一种体质说法, 是你肝里有多少条流水线。
临床差异 (Cornelis 2006 JAMA, N=4 080, 哥斯达黎加 MI 队列):
慢代谢者 (CC) 喝 4+ 杯咖啡 / 天 → 心梗风险 ↑ 36% (vs 不喝)快代谢者 (AA) 喝 4+ 杯 → 心梗风险 ↓ 22% (反向!)中间型 (AC): 与不喝者风险接近
这是营养医学最清晰的药物基因组学例子——同样饮食, 基因型不同, 健康结果反向。
这一条也顺带解释了为什么咖啡到底好不好这个问题在人群研究里吵了几十年: 把两类人混在一个平均值里, 一个方向的风险和另一个方向的保护会互相抵消, 剩下的那个没有显著差异其实是两条相反的曲线叠出来的。
慢代谢者其它表现:
下午、晚上喝咖啡显著影响睡眠心悸 + 焦虑更常见急性血压反应大喝完心慌几乎一定是 CC 基因型妊娠期高血压风险也与 CYP1A2 慢代谢 + 高咖啡因摄入相关
快代谢者:
晚上喝咖啡也能睡 通常是真的运动表现 咖啡因效应更小, 需要更高剂量部分研究: 心血管事件似乎获保护 (但要看具体剂量 + 整体饮食)
怎么知道自己的基因型:
23andMe / AncestryDNA + Promethease/SNPedia: 看 rs762551国内: WeGene / 微基因基因检测公司: 价格 ~ $50-150
实操调整:
慢代谢者:截止时间: 上午 11 点之前每日上限: 200 mg (~ 1.5 杯滴漏)必备 L-theanine: 200 mg 平衡焦虑避免: 高咖啡因运动饮料、能量饮料、浓缩咖啡多杯
快代谢者:截止时间: 下午 2 点 (常规)每日上限: 400 mgL-theanine: 可选, 个体偏好运动: 可考虑赛前 200-400 mg
Coffee + CV complex relationship
Why coffee research keeps producing contradictory results:Early studies (1980s-90s): multiple cohort studies linked coffee with increased cardiovascular mortality →
"Drink less coffee" became mainstream advice
2000s-2010s: more rigorous studies started adjusting for confounders:
Coffee drinkers were also more likely to smoke, not exercise, and eat more sugarOnce those were controlled for, coffee's independent effect reversed
Poole 2017 *BMJ* meta-analysis (200+ studies, N > 10 million):
3-4 cups per day was associated with:All-cause mortality ↓17%Cardiovascular mortality ↓19%Some cancers (liver, endometrial) ↓Type 2 diabetes ↓Parkinson disease ↓> 5 cups per day in pregnancy: increased preterm birth risk
Key insight:
Overall, coffee trends favorable for most peopleExcept CYP1A2 slow metabolizers — at the same dose, the risk direction reverses"Is coffee good for me" is not a single answer — it depends on dose + genotype + overall diet
Coffee is not just caffeine:
Chlorogenic acid: antioxidant — part of the glucose-handling benefitTrigonelline + roasting byproducts: anti-inflammatory — part of the metabolic benefitDiterpenes (cafestol + kahweol): in unfiltered coffee (French press, Turkish), they significantly raise LDLDrip / espresso (with paper or metal filter) is the safer choiceFrench press 2-3 cups/day over the long term → LDL can rise 6-8 mg/dL
Decaf:
Contains 0-15 mg caffeine per cup (vs 95-150 for regular)Retains most polyphenols + chlorogenic acidSome cohort studies show decaf also has cardiovascular and T2D protectionGood fit for slow metabolizers and anyone who wants the evening flavor without the kickThe Swiss Water Process is solvent-free and preferred
Practical guidance:
Most people: 3-4 drip cups per day is a fine habit, provided:You are not a CYP1A2 slow metabolizerYou don't add heavy sugar or artificial sweetenersIt isn't replacing water or a healthy overall dietSlow metabolizers: 1-2 cups + some decaf + some teaPregnant: ACOG < 200 mg/day (~1.5 drip cups)Diagnosed insomnia / anxiety: cut down to 100 mg/day or go fully decaf and reassess
poole-2017-coffee-umbrella
Chapter 5
Use cases · study / work / sport
Use cases · study / work / sport
Concrete use cases for caffeine + L-theanine:
【Deep work / study / writing】
Goal: 2-4 h of sustained focus, no anxiety, no drowsinessProtocol: caffeine 100 mg + L-theanine 200 mg, 30 minutes before startingNote: drink plain water alongside, take food breaksLess useful for: idea generation. The randomised trial that actually tested this (Zabelina 2020, 200 mg vs placebo, n=88) found caffeine significantly improved convergent problem solving and had no significant effect on creative generation — so it does not help brainstorming, but there is no evidence it hurts
【Exams / interviews / important meetings】
Goal: 1-2 h peak performance + controlled anxietyProtocol: caffeine 75 mg + L-theanine 150 mg, 30-45 minutes beforeDo not try a new combination on the day: use a protocol you already know; new supplements on key days can backfireAvoid: a big caffeine dose (palpitations and nerves cost more points than they buy)
【Sport performance】
Endurance: caffeine 3-6 mg/kg (60 kg = 180-360 mg), 30-60 minutes pre-eventStrength training: same dose range, but smaller effectL-theanine usually unnecessary — the sport context cares about activation, not anxiety control"Stop caffeine for 1 week before competition": lets receptors reset → effect on the day is stronger
【Afternoon slump】
The 1-2 pm "post-lunch dip" is a natural circadian featureOption A: a strong cup of tea (caffeine 50 mg + natural theanine 15 mg) + a 10-minute walkOption B: a short nap of 15-20 min (no longer than 30, or sleep inertia kicks in)Avoid: a third coffee — 50% is still in your body at 9 pm and disrupts deep sleep
【Coping with jet lag】
Eastward flights: coffee + bright light the morning you arrive → anchors the new circadian phaseWestward flights: avoid caffeine pre-bedtime at the destinationDon't: drink coffee on the plane and then try to sleep
【Anxious users who want alertness without making anxiety worse】
Protocol: L-theanine 200 mg alone (no caffeine) + a cup of herbal teaEffect: alert but relaxed, α-wave ↑Alternative: a walk, sunlight, splashing cold water on the face
【Caffeine-sensitive users going completely off】
5-7 days of uncomfortable withdrawalBaseline alertness should then improve, not get worseIf you're 4 weeks fully off and still drowsy / poor focus → screen for sleep apnea, hypothyroidism, iron deficiency, B12 deficiency, or depression
When you should not use this stack:
On an SSRI or MAOI: use cautionHistory of arrhythmia / atrial fibrillation: reduce or avoidSevere anxiety disorder / panic: full elimination may improve symptomsPregnant / breastfeeding: < 200 mg caffeine, L-theanine from tea onlyChildren under 12: no caffeine supplementsTeens 12-18: < 100 mg/dayCertain medications (fluvoxamine, quinolone antibiotics, cimetidine): these inhibit CYP1A2 → caffeine half-life can soar to 30+ h
【Deep work / study / writing】
Goal: 2-4 h of sustained focus, no anxiety, no drowsinessProtocol: caffeine 100 mg + L-theanine 200 mg, 30 minutes before startingNote: drink plain water alongside, take food breaksLess useful for: idea generation. The randomised trial that actually tested this (Zabelina 2020, 200 mg vs placebo, n=88) found caffeine significantly improved convergent problem solving and had no significant effect on creative generation — so it does not help brainstorming, but there is no evidence it hurts
【Exams / interviews / important meetings】
Goal: 1-2 h peak performance + controlled anxietyProtocol: caffeine 75 mg + L-theanine 150 mg, 30-45 minutes beforeDo not try a new combination on the day: use a protocol you already know; new supplements on key days can backfireAvoid: a big caffeine dose (palpitations and nerves cost more points than they buy)
【Sport performance】
Endurance: caffeine 3-6 mg/kg (60 kg = 180-360 mg), 30-60 minutes pre-eventStrength training: same dose range, but smaller effectL-theanine usually unnecessary — the sport context cares about activation, not anxiety control"Stop caffeine for 1 week before competition": lets receptors reset → effect on the day is stronger
【Afternoon slump】
The 1-2 pm "post-lunch dip" is a natural circadian featureOption A: a strong cup of tea (caffeine 50 mg + natural theanine 15 mg) + a 10-minute walkOption B: a short nap of 15-20 min (no longer than 30, or sleep inertia kicks in)Avoid: a third coffee — 50% is still in your body at 9 pm and disrupts deep sleep
【Coping with jet lag】
Eastward flights: coffee + bright light the morning you arrive → anchors the new circadian phaseWestward flights: avoid caffeine pre-bedtime at the destinationDon't: drink coffee on the plane and then try to sleep
【Anxious users who want alertness without making anxiety worse】
Protocol: L-theanine 200 mg alone (no caffeine) + a cup of herbal teaEffect: alert but relaxed, α-wave ↑Alternative: a walk, sunlight, splashing cold water on the face
【Caffeine-sensitive users going completely off】
5-7 days of uncomfortable withdrawalBaseline alertness should then improve, not get worseIf you're 4 weeks fully off and still drowsy / poor focus → screen for sleep apnea, hypothyroidism, iron deficiency, B12 deficiency, or depression
When you should not use this stack:
On an SSRI or MAOI: use cautionHistory of arrhythmia / atrial fibrillation: reduce or avoidSevere anxiety disorder / panic: full elimination may improve symptomsPregnant / breastfeeding: < 200 mg caffeine, L-theanine from tea onlyChildren under 12: no caffeine supplementsTeens 12-18: < 100 mg/dayCertain medications (fluvoxamine, quinolone antibiotics, cimetidine): these inhibit CYP1A2 → caffeine half-life can soar to 30+ h
六个场景 · 各自的配比与时间
咖啡因 + L-theanine 的几个具体使用场景:【深度工作、学习、写作】
目标: 长时间 (2-4 小时) 高注意力 + 不焦虑 + 不嗜睡方案: caffeine 100 mg + L-theanine 200 mg, 开始工作前 30 分钟注意: 加无咖啡因水 + 食物间歇帮不上的: 想点子。真正做过这件事的随机双盲试验 (Zabelina 2020, 200 mg vs 安慰剂, n=88) 的结果是: 咖啡因让收敛式解题显著变好, 对发散式想点子则测不到影响
这一条值得停一下, 因为它和直觉差半步: 咖啡因擅长的是把注意力收窄并按住, 所以写代码、对账、啃论文它帮得上; 而想点子、找类比、换个角度需要念头四处乱撞, 它给不了这个。但要分清两件事: 测不到帮助和会妨碍不是一回事 —— 那项试验并没有测出它损害发散思维。前者是别指望它, 后者是那段时间别喝, 而证据只支持前一句。
【考试、面试、重要会议】
目标: 短时间 (1-2 小时) 峰值表现 + 焦虑控制方案: caffeine 75 mg + L-theanine 150 mg, 30-45 分钟前不要尝试新组合: 在重要日子之前用已经熟悉的方案; 突然加新补剂可能反效果避免: 大量咖啡因 (心悸、紧张反而扣分)
【运动表现】
耐力运动: caffeine 3-6 mg/kg (60 kg = 180-360 mg), 30-60 分钟前力量训练: 同上, 但效应较小L-theanine 通常不需要——运动场景不在乎焦虑, 在乎激活赛前停咖啡 1 周: 让受体回归基线 → 比赛日效果更强
【午后困倦】
下午 1-2 点的post-lunch dip 是自然昼夜节律方案 A: 浓茶 (caffeine 50 mg + 自然 theanine 15 mg) + 散步 10 分钟方案 B: 短小睡 15-20 分钟 (不超过 30, 避免 sleep inertia)避免: 第三杯咖啡 → 晚 9 点仍有 50% 体内 → 干扰深睡
午后那阵困不是你早上的咖啡失效了, 它是昼夜节律自己排的一段低谷, 所以拿咖啡去填往往性价比很差: 你付出的是当晚的深睡, 换来的是一段本来就会自己过去的低谷。散步和小睡之所以在这里排在咖啡前面, 原因就是它们不向今晚借钱。
【应付时差】
东向飞行: 抵达后晨起咖啡 + 强光暴露 → 帮助锚定新昼夜西向飞行: 抵达后睡前避免咖啡因不要: 在飞机上喝咖啡 + 想睡觉
【焦虑 + 想要提神但怕加重焦虑】
方案: L-theanine 200 mg 单独 (无咖啡因) + 一杯花草茶效应: 警觉但放松, alpha 波 ↑替代: 散步 + 阳光暴露 + 冷水洗脸
【对咖啡因敏感者完全戒】
戒断 5-7 天痛苦期之后基线警觉性应该改善, 不是变差如果完全戒 4 周后仍然嗜睡、注意力差: 排查睡眠呼吸暂停、甲减、缺铁 / B12 / 抑郁
最后这条是个分诊逻辑, 值得记住: 咖啡因会盖住疲劳信号, 所以它同时也盖住了你为什么累这个问题的线索。彻底戒掉之后如果精力自己回来了, 那原来的问题就是咖啡因和睡债; 如果戒干净了还是累, 那说明疲劳另有来源, 该去查的是上面那几项, 而不是换一款更贵的提神补剂。
Summary · practical decisions
Caffeine + L-theanine — practical decision checklist:1. Do I actually need a supplement?
If you already drink 2-3 cups of green tea or matcha per day, you have a mild built-in caffeine + theanine synergyAdd an L-theanine capsule only when: you want to drink coffee (high caffeine) and dampen the anxietyPure alertness: one cup of coffee or strong tea is enough — no supplement needed
2. What's my baseline alertness?
Enough sleep + regular exercise → you'll be alert without caffeineSleep debt + sedentary → any supplement is just borrowed money, not a fix"I can't function without coffee" = the alertness system is broken, not a coffee problem
3. What's my CYP1A2 phenotype?
Slow metabolizer (palpitations, anxiety, can't sleep after evening coffee): strict < 200 mg/day, always pair with L-theanineFast metabolizer (no reaction): the standard protocol worksUnknown: 2 weeks of self-observation
4. What's my goal?
Sustained focus: 1:2 ratio, split dosesPeak performance: 1:1 ratioMorning lift: 1:1 or pure caffeineAfternoon buffer: 1:3 (theanine-leaning)Evening social setting: tea or decaf
5. Actual dose + timing?
Beginner: caffeine 50 mg + L-theanine 100 mg, in the morningExperienced: caffeine 100-200 mg + L-theanine 200-400 mgOver 400 mg caffeine/day: reassessNever after 2 pm (unless you're a fast CYP1A2 and sleep is unaffected)
Things to avoid:
Energy drinks (Red Bull, Monster): high caffeine + high sugar + many additives — not recommendedCaffeine pills (NoDoz, ProPlus): 200 mg in one go — easy to overshoot"Pre-workout" compound supplements: caffeine 200-400 mg + β-alanine + assorted stimulants — side-effect risk is high, and the upside is unnecessaryPre-bed coffee + a sleep aid: directly fights your circadian rhythm
Final principle:
> Caffeine + L-theanine are adjuncts, not a lifestyle.
> When you can't be alert without them, the real problem lives in your sleep / exercise / psychology / nutrition baselines. Fix those four, and you may not need them at all.
zabelina-2020-caffeine-creativity
References · 6
- Nehlig, A. (2018). Interindividual differences in caffeine metabolism and factors driving caffeine consumption. Pharmacological Reviews, 70(2), 384–411. 10.1124/pr.117.014407
- Cornelis, M. C., El-Sohemy, A., Kabagambe, E. K., & Campos, H. (2006). Coffee, CYP1A2 genotype, and risk of myocardial infarction. JAMA, 295(10), 1135–1141. 10.1001/jama.295.10.1135
- Owen, G. N., Parnell, H., De Bruin, E. A., & Rycroft, J. A. (2008). The combined effects of L-theanine and caffeine on cognitive performance and mood. Nutritional Neuroscience, 11(4), 193–198. 10.1179/147683008X301513
- Nathan, P. J., Lu, K., Gray, M., & Oliver, C. (2006). The neuropharmacology of L-theanine (N-ethyl-L-glutamine): a possible neuroprotective and cognitive enhancing agent. Journal of Herbal Pharmacotherapy, 6(2), 21-30. 10.1080/j157v06n02_02
- Kelly, S. P., Gomez-Ramirez, M., Montesi, J. L., & Foxe, J. J. (2008). L-theanine and caffeine in combination affect human cognition as evidenced by oscillatory alpha-band activity and attention task performance. The Journal of Nutrition, 138(8), 1572S–1577S. 10.1093/jn/138.8.1572S
- Haskell, C. F., Kennedy, D. O., Milne, A. L., Wesnes, K. A., & Scholey, A. B. (2008). The effects of L-theanine, caffeine and their combination on cognition and mood. Biological Psychology, 77(2), 113–122. 10.1016/j.biopsycho.2007.09.008