This morning over at Gizmodo, Ph.D. candidate Steven Miller explains the “best” time to drink coffee in fascinating detail. It has to do with chronopharmacology — or, roughly, the efficacy of drugs at different times of day — and cortisol, a naturally occurring stress hormone that increases alertness.
Since our cortisol levels naturally spike between 8 AM and 9 AM (and again between noon and 1 PM, and between 5:30 and 6:30 PM), it would not behoove the clever coffee drinker to consume their brew during this time. The average person is already naturally at maximum levels of alertness.
Therefore, Miller says, the most effective time to drink coffee is between 9:30 and 11:30 AM, when your cortisol levels are dropping off before their next spike. Writes the author–
Drug tolerance is an important subject, especially in the case of caffeine since most of us overuse this drug. Therefore, if we are drinking caffeine at a time when your cortisol concentration in the blood is at its peak, you probably should not be drinking it. This is because cortisol production is strongly related to your level of alertness and it just so happens that cortisol peaks for your 24 hour rhythm between 8 and 9 AM on average… Therefore, you are drinking caffeine at a time when you are already approaching your maximal level of alertness naturally.
Despite the post’s meticulousness, Miller does leave us wondering — as one reader pointed out in the comments — what if you wake up after 9 AM? Are cortisol levels still flying high, regardless of whether or not one is sleeping? Steven’s post is likely based on the average 24-hour biological cycle; waking after 9 AM may be an outlier, in which case I’m one over 50% of the time.