What do you do when it’s late into the evening the day before a big project is due? If you’re a good little worker, you rest easy because everything is already taken care of, but for those of us who have perfected the art of procrastination, it’s time to pull an all-nighter. And what is your beverage of choice when you want to stay awake? For a lot of people, the answer is a strong cup of coffee.

However, what many view as a miracle mug of liquid energy can actually have the opposite effect! In Natsuko Kasai’s book Sweet things are Bad for the Brain, the certified nutritionist and meal counselor explains how drinking coffee has an unexpected side-effect that can wear you out more than wake you up.

So why is coffee bad for all-nighters? Basically, the caffeine in coffee induces diuresis. In other words, it makes you have to pee. Sure, it’s nice to take a break and stretch your legs as you work beyond your bedtime, but disrupting your workflow for a quick run to the bathroom is not the way to do it. Annoying in its own right, this actually causes an even greater problem for your health, in that every time you relieve yourself, you’re losing water. As you become more and more dehydrated, your blood thickens and moves more slowly through your veins. This means that your body is using oxygen at a slower rate, and thus it becomes sluggish.

Now, we shouldn’t entirely disregard the stimulating effects of caffeine. It is a drug that activates sympathetic nerves, which make you feel more awake. It comes like a shock to the system, but a short time later, the effects wear off, and you need more, so you make yourself another cup of coffee. The more you drink, the more you pee. The more you pee, the less water you have in your system. Less water means slower blood flow, and this makes you even more tired than before. Drinking coffee to stay awake becomes a vicious cycle doomed to fail. For you see, taking in more and more caffeine wears out the nervous system until those sympathetic nerves are numb to the drug. At that point, drinking coffee won’t even give you that initial burst of energy but will simply fill your bladder.

So what can you drink instead?

Kasai encourages people to stay away from all caffeinated beverages when trying to stay awake for long periods of time. If you want to stay hydrated and keep yourself alert in the long run, then you need to avoid caffeine. Drinks that have high sugar content also do not come recommended. The sudden rise and fall of your blood sugar levels that comes after having something like a sports drink can badly impact your ability to focus on the task at hand.

When you feel it necessary to work through the night, water and non-caffeinated teas are your absolute best bet. Save the sweetened double shot espresso for another time.

Source: WooRis (Japanese)