New science shows your morning coffee may be more effective depending on when you drink it. A study published in the journal Psychosomatic Medicine shows coffee hits us hardest in the mid-morning, between 9:30 and 11:30 am.
The culprit here is a hormone called cortisol. Cortisol is released in response to stress, helping the body convert stored energy into glucose. It also influences our body’s circadian rhythms, telling us when to be alert or when to be sleepy. When cortisol levels are low in the body, making us feel more sluggish, we feel the effects of coffee more acutely than when cortisol levels are elevated.
Cortisol levels tend to spike upon waking and remain elevated for roughly an hour. Therefore, to best feel coffee’s effects, we should drink when cortisol is lowest, between one and three hours after waking. Cortisol also spikes around lunch and again around dinnertime, mitigating coffee’s effects.
On his blog, neuroscientist PhD student Steven Miller extrapolates further upon these findings. “When …cortisol…is at its peak, you probably shouldn’t [drink coffee]. 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. The same cup of morning coffee will become less effective [when cortisol levels are high].”
Cortisol levels, and therefore the punch in a cup of coffee, vary not only by time of day, but from person to person as well. Night-owls who work into the wee hours and sleep late usually experience cortisol spikes later than the early-birds up before the sun.
The takeaway from all this is that coffee is best experienced by well-rested mellow people during brunch hours. Low stress a few hours after waking depletes our cortisol, making our cup of dark-roast Sumatran all the better.