This article says differently:
Wake up and smell the coffee beans. Many of us start the day in this manner, but sometimes that caffeine kick we’re after doesn’t actually kick. Turns out there’s a good reason – if you’re missing out on an energy boost from that morning cup, science has the answer.
The daily coffee habit isn’t just a delicious ritual, it’s also a vehicle for the planet’s most popular psychoactive drug, caffeine. People the world over rely on this central nervous system stimulant for its ability to keep them alert, despite the myriad side effects including possible anxiety and heartburn (everything in moderation, people).
However, as anyone who’s not a coffee addict will attest, humans are perfectly capable of staying awake without chemical help. This is thanks to our own internal chemistry, and, more specifically, a hormone called cortisol.
As with any hormone, cortisol has several influences on the body, and is most commonly associated with metabolism. Produced in the adrenal cortex above the kidneys, it also plays a role in our stress and alertness levels.
And this is where it gets really interesting. Research has found that cortisol has a natural peak-and-fall cycle in the human body, with the highest levels occurring on average between 8 to 9 am.
Cortisol – and therefore your natural, unaided alertness levels – are important to consider in relation to your caffeine intake. Right when you wake up, your cortisol is already on the climb, which means that the morning coffee shot is going to have a lesser effect.
“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,” writes neuroscientist Steven L. Miller. “One of the key principles of pharmacology is use a drug when it is needed [..] Otherwise, we can develop tolerance to a drug administered at the same dose.”
So drinking coffee first thing in the morning makes you more resistant to its effects. Of course, if you’re just drinking it for the taste, go nuts.
But when should you enjoy your coffee, then?
To optimise your coffee break, it’s best to have it between 9.30 and 11.30am. Because cortisol levels peak and rise a couple times during the day, your next window of alertness is between noon and 1pm, and then again between 5.30 and 6.30pm.
Drink coffee in-between these times to reap maximum caffeine benefits, but don’t leave it too late in the day if you want to get a good night’s sleep.
Am I likely to change my habits? Probably not. My cortisol levels have been screwed up for over 30 years anyway!