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.
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
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.
Science of drinking caffeine
Caffeine doesn't stimulate your brain; it just suppresses the part that makes you drowsy, as the video above shows.
To be more scientific about best using caffeine to stay alert, try inputting some information into the Coffee Kick Calculator to find out when the optimum caffeine consumption times are for you. Enter how much sleep you got, when you woke up and then play around with which caffeinated drinks (coffee, soda, tea, energy drink) you typically drink and at what time. A chart will pop up showing you your alertness throughout the day. Plug in drinks earlier or later in the day to see if you'll be more alert when you need to be if you change your drinking times.
The formula used in the calculator was developed by scientists in the U.S. Army Medical Research and Materiel Command in Fort Detrick, Maryland. Because about 40 percent of U.S. soldiers sleep only five hours a day, researchers studied several caffeine doses in different sleep deprivation scenarios. In their study, they created an algorithm that they found can improve performance by as much as 64 percent.
You can predict how much caffeine you should drink — and when — to reach peak alertness.
