why should i wait with my coffein intake 90 minutes?

Waiting 90–120 minutes after waking may help you get a steadier stretch of energy through the day, avoid an afternoon crash, and protect sleep by reducing the urge for later caffeine. 1

• 1. Natural waking processes: Sleep lowers adenosine, but some remains when you wake. Caffeine blocks adenosine’s effects without clearing it; Huberman’s explanation is that waiting allows the morning cortisol rise and related processes to clear residual adenosine before you use caffeine. 2 3 4
• 2. Afternoon crash and extra caffeine: Taking caffeine immediately can mask sleepiness while adenosine accumulates; as caffeine wears off, that may contribute to a sharper afternoon dip. Delaying intake may provide a more consistent arc of energy and reduce the need for another dose. 5 6
• 3. Sleep later that night: Caffeine has a roughly 12-hour quarter-life, so some of its effects can remain many hours later. Avoiding extra afternoon caffeine can help limit its potential to disrupt nighttime sleep quality. 7 8