How Caffeine Works In Your Body
Caffeine works in three steps:
- Adenosine builds up as you work and move throughout the day
- Caffeine blocks adenosine receptors — stopping the "tiredness" signal reaching your brain
- You feel alert and focused — but the tiredness is still there, just delayed
Half-life: ~5–7 hours. A coffee at 2pm is still 50% active in your system at 9pm. This is why timing matters as much as amount.
Proven Performance Benefits (when used correctly)
- Improved endurance (+2–4%)
- Enhanced focus & reaction time
- Increased fat oxidation
- Better short-term memory
- Reduced perceived effort
Your Daily Caffeine Budget
| Level | Amount | What it means |
|---|---|---|
| Low | 0–100mg | Under-caffeinated |
| Optimal | 100–240mg | Sweet spot for most people |
| High | 240–340mg | Approaching dependency territory |
| Limit | 340–400mg | Maximum recommended for healthy adults |
Max recommended: 400mg per day for healthy adults.
Athletes may use up to 6mg/kg of body weight pre-performance.
Caffeine in Common Drinks
| Drink | Caffeine |
|---|---|
| ☕ Espresso (single) | 63mg |
| ☕ Filter Coffee (250ml) | 95mg |
| ☕ Flat White | 130mg |
| 🍵 Green Tea (250ml) | 35mg |
| 🍵 Black Tea (250ml) | 47mg |
| 🍵 Matcha Latte | 70mg |
| ⚡ Energy Drink (250ml) | 80mg |
| ⚡ Pre-Workout (1 scoop) | 200mg |
| 🥤 Cola (330ml) | 35mg |
| 🍫 Dark Chocolate (50g) | 25mg |
Perfect Timing Window
The Daily Caffeine Clock
| Time | Zone | What to do |
|---|---|---|
| Wake – 9am | Cortisol + Sleep Zone | No caffeine |
| 7:30am – 9am | Cortisol Peak | Skip caffeine here specifically |
| 9am – 2pm | OPTIMAL WINDOW | This is your window |
| 2pm – 4pm | Last Chance | Only if you have high tolerance |
| 4pm onwards | Avoid | Sleep quality will suffer |
The 90-Minute Morning Rule
Don't caffeinate straight after waking.
Cortisol peaks 30–45 mins after waking. Caffeine during this window blunts its effect and builds tolerance faster. Wait 90 minutes after waking for your first coffee. Use morning light and movement instead.
Caffeine Curfew: 2pm
Caffeine's 5–7hr half-life means a 2pm coffee is still 50% active at 9pm — directly impairing deep sleep quality.
Athlete Protocol
- Wake → 90 min wait → First coffee
- Pre-workout: 3mg/kg, 30–60 min before training
- No caffeine after 2pm on training days
Too Much? Warning Signs
| Sign | What it looks like |
|---|---|
| Jitteriness | Hands shaking or heart racing |
| Anxiety spike | Elevated stress or panic feelings |
| Poor sleep | Trouble falling or staying asleep |
| Headaches | Especially when you skip a dose |
| Heart palpitations | Irregular or fast heartbeat |
| Irritability | Low mood when caffeine wears off |
| Digestive issues | Acid reflux or urgency |
Smarter Swaps
Reduce dependency without losing focus
| Time of day | Swap to |
|---|---|
| Early morning | Water + sunlight |
| Mid-morning | Matcha latte (~70mg) |
| Post-lunch dip | Cold water + a walk |
| Afternoon | Decaf or herbal tea |
| Evening | Chamomile / ashwagandha tea |
Dependency vs Habit
If you feel you need caffeine to function, you're dependent — not energised.
True energy comes from sleep, movement, and whole food nutrition. Caffeine should enhance performance, not replace recovery.
The Caffeine Reset
2-week step-down — no crash, no misery
Week 1
| Days | Action |
|---|---|
| Days 1–2 | Cut total intake by 25% |
| Days 3–4 | Push first coffee to 10am |
| Days 5–7 | Remove all caffeine after 1pm |
Week 2
| Days | Action |
|---|---|
| Days 8–9 | Reduce to 1–2 coffees max |
| Days 10–11 | Swap one for matcha or green tea |
| Days 12–14 | Optional 2-day full break |
5 Habits to Start Today
- Delay your first coffee 90 mins after waking
- Track mg — not just cups
- Set a hard 2pm caffeine cut-off
- Take 1–2 caffeine-free days per week
- Pair caffeine with food — never fasted
Want to Go Deeper?
Subscribe to Brad Brassica on YouTube for more on mindful dieting, gut health, and habit change.
View YouTube Channel