The U.S. Army has developed an algorithm that determines how much coffee a person should drink — and when you should drink it — for optimal benefits. But since they’re keeping that top-secret information close to the chest for now, we thought it made sense to take a more transparent and scientific approach to the question.
On a normal weekday morning, you probably wake up just a little bit tired. What do you do? You drink coffee in the morning to get more alert. But not so fast. Just because you've always done something a certain way, doesn't mean it's the right way. That's why we have the scientific method!
Circadian rhythm is a factor
The best time to drink coffee is when your brain can use the caffeine most efficiently, and that's not first thing in the morning. In fact, drinking coffee at that time undermines its effectiveness, and your body builds up a tolerance more quickly. That's because our natural alertness is caused by the fluctuations in our hormones throughout the day, and the morning is when they are already naturally higher.
As the video above explains, cortisol is one of the key hormones in our circadian clocks, our sleep-awake cycle, which naturally cycles throughout the day. Generally, there's more cortisol cycling around in the morning to help you wake you up, and it slacks off at night, to help you feel tired and want to sleep. The problem arises when you regularly use caffeine in the morning, which interferes with the body's production of cortisol. You end up producing less cortisol just when you need it the most.
So you're taking in the caffeine when it's least effective, which dampens its effects. Even worse, over time, the body comes to rely on the caffeine boost (rather than letting the cortisol do its job), which is why you develop a caffeine dependence.
And if you're thinking that you've been drinking coffee for years and "can't wake up without it" that's because your natural cortisol cycle has been disrupted, not because you wouldn't normally be alert at that time. Of course, this is all assuming you're getting a reasonable amount of sleep. You have effectively trained your body to expect a caffeine jolt at the start of the day and now your body is used to it. Over time, you may find that you need more and more coffee for the same effect.
Later in the day is better
A graph of cortisol variation throughout the day. Cortisol helps you wake up in the morning, and it is at its peak then. It bottoms about 10 a.m. or noon, making that time the best time for a coffee break. (Photo: Journal of Clinical Endrocrinology and Metabolism)
For most people, the worst time to drink coffee is between 6 a.m. and 10 a.m., though circadian rhythms vary by person depending on their sleeping patterns. So when is the best time?
As Roberto Ferdman at the Washington Post writes, "It's during the troughs above — between roughly 10 a.m. and noon, and 2 p.m. and 5 p.m. — when people should drink coffee if they want to get the most out of their caffeine. Between those hours, the coffee is actually most needed, and, perhaps most importantly, will not interfere with our body's own essential mechanism for keeping us alert."
So if you want to use coffee to best effect, and with a lower likelihood of dependence, drink your coffee in the early afternoon — unless, of course, you find that it interrupts your sleep cycle at night. If you want to get your body back on a more natural cortisol schedule, you can try slowly moving the timing of your first cup over the course of a week or two. That way you don't have to go through an uncomfortable withdrawal headache.
From my own one-person data set, I can back up these findings. On most days I drink green tea in the morning, around 10 a.m. after about an hour of work, and then enjoy a coffee or black tea at around 3 p.m. I've been doing this for about three years and haven't needed more coffee or tea year-over-year to enjoy the same effects, and I also don't have trouble waking up in the morning.
Editor's note: This article has been updated since it was originally published in June 2015.