Caffeine
The world's most consumed psychoactive drug. Caffeine blocks adenosine, the signal that tells your brain you're tired—but there's a price to pay.
How Caffeine Works
Adenosine Blocking
Adenosine builds up while you're awake, signaling tiredness. Caffeine has a similar molecular shape and blocks adenosine receptors. You feel awake—but adenosine keeps building. When caffeine wears off, all that adenosine hits at once: the crash.
Dopamine Boost
By blocking adenosine (which normally inhibits dopamine), caffeine indirectly increases dopamine signaling. This is why coffee feels motivating and mood-lifting. It's also why caffeine is mildly addictive.
Caffeine Metabolism: Fast vs Slow
The CYP1A2 enzyme determines how quickly you metabolize caffeine. Genetic variants create fast and slow metabolizers—with very different health outcomes.
Fast Metabolizers
- • Clear caffeine quickly (2-4 hour half-life)
- • Can drink coffee late with less sleep impact
- • May benefit from moderate coffee consumption
- • Need more caffeine for same effect
- • Coffee associated with reduced heart disease risk
Slow Metabolizers
- • Clear caffeine slowly (8-12 hour half-life)
- • Afternoon coffee ruins sleep
- • More prone to jitters and anxiety
- • Coffee associated with INCREASED heart disease risk
- • Should limit to 1 cup, morning only
✅ Potential Benefits (Used Wisely)
Alertness & Focus
Blocks adenosine, increases dopamine and norepinephrine signaling.
Physical Performance
Increases adrenaline, mobilizes fatty acids. 3-6% performance boost.
Antioxidants
Coffee is a major source of polyphenols in Western diets.
Liver Protection
Associated with reduced risk of liver disease and cirrhosis.
Parkinson's Prevention
Caffeine is associated with reduced Parkinson's risk—adenosine link.
Mood Enhancement
Moderate use associated with reduced depression risk.
⚠️ The Downsides
Sleep Destruction
Even 6 hours before bed, caffeine reduces deep sleep by 20%. Blocks adenosine's sleep-promoting effects.
Cortisol Spike
Raises cortisol, especially in the morning. Amplifies stress response. Worsens adrenal fatigue.
Anxiety & Jitters
High doses trigger anxiety, especially in slow metabolizers or those with COMT variants.
Mineral Depletion
Increases urinary excretion of magnesium, calcium, potassium. Blocks iron absorption.
Dependency
Brain upregulates adenosine receptors. Need more caffeine for same effect. Withdrawal headaches.
Blood Pressure
Acutely raises blood pressure. Problematic for slow metabolizers and those with hypertension.
Optimal Caffeine Strategies
Delay Morning Coffee
Wait 90-120 minutes after waking. Let cortisol peak naturally first. Caffeine on top of high cortisol = double stress response.
Cutoff Time
No caffeine after 2pm (or noon for slow metabolizers). It's still in your system at bedtime.
Cycle Off Periodically
Take 1-2 weeks off every few months. Reset adenosine receptors. Caffeine works better after a break.
Supplement Minerals
If you drink coffee regularly, supplement magnesium. Separate coffee from iron-rich meals by 1+ hours.
Caffeine Content Guide
Coffee (8oz)
95-200mg
Black Tea (8oz)
40-70mg
Dark Chocolate (1oz)
20-25mg
Energy Drink
80-300mg
Metabolic Connections
Dopamine
Caffeine increases dopamine signaling by blocking adenosine
Cortisol
Caffeine elevates cortisol, especially when consumed early
Magnesium
Caffeine increases urinary magnesium excretion
Iron
Coffee/tea polyphenols block iron absorption
Sleep
Caffeine blocks adenosine, disrupting sleep architecture
Anxiety
Excess caffeine can trigger or worsen anxiety