Key Takeaway
Morning caffeine amplifies the natural cortisol awakening response; delaying caffeine 90-120 minutes allows cortisol to peak naturally first.
Summary
This study examined how caffeine interacts with the body's natural cortisol rhythm throughout the day.
Caffeine consumption increases cortisol secretion, and this effect is most pronounced in the morning when cortisol is naturally elevated. Timing caffeine after the natural cortisol peak may optimize both systems.
Methods
- Repeated measures design
- Cortisol sampling throughout day
- Caffeine vs placebo conditions
- Multiple timepoints
Key Results
- Caffeine elevates cortisol
- Morning effect most pronounced
- Effects persist for hours
- Individual variation exists
Figures
Figure 1
Figure 2
Limitations
- Controlled setting
- Fixed caffeine doses
- Acute effects measured