How caffeine and water can make or break your mental energy

When it comes to optimizing our mental energy around the clock, there are three powerful synchronizers. As I explained last week, light is the most powerful of these so-called time givers.

By setting off a fascinating dance between cortisol (the "waking-up hormone") and melatonin (the “hormone of darkness”), getting light right is vital for being at our best throughout the day and deeply asleep at night. 

Nutrition is the second most powerful time giver for controlling our mental energy. When you think about it systematically, you can pull three levers regarding drinking and eating: timing, quality and quantity. 

How we pull these levers, it turns out, is not only vital for our health. Used strategically, they help us control our mental energy by maintaining relatively high levels during the day and lower levels toward the night.

Employed haphazardly, they can do the exact reverse.

The opposite of stress eating

You’re probably familiar with the term stress eating: When stressed out, many people tend to eat more (unhealthy) food to calm themselves down. 

In today’s and the following posts, I’ll describe how you can flip this concept on its head. Instead of eating as a reaction to stress, you’ll learn to leverage nutrition to get your mental energy where you want it to be and thus minimize stress in the first place.

Let me explain. A lot of what we label stress occurs when our internal state (i.e., our mental energy) does not match the external demands put upon us. If we want to be productive in the morning or afternoon but have a low or unstable level of mental energy, this creates stress. Conversely, if we want to fall asleep in the evening while our minds or bodies are still working at full speed, we’ll have problems winding down, which also feels stressful.

Now, our nutrition plays a vital role in creating both types of stress. You probably know that from first-hand experience. One example is the roller coaster ride in blood glucose after a (sugary) breakfast in the morning. A second is the food coma in the afternoon. And a third is the trouble we have with falling asleep after a too-big (or too-small) meal in the evening.

As these examples show, when, what and how much we ingest is one of the most important factors influencing our level of autonomic arousal.

Here’s what to expect:
In today’s post, you’ll learn how to strategically use caffeine and water to optimize your mental energy throughout the day. Next week, I’ll explain how to pull off the same trick for eating – and fasting – actual food. And in the following week, I'll delve deeper into how specific kinds (and quantities) of the food we eat impact our mental energy.

Let’s dive right in.

The dance between caffeine and adenosine

Although there is a lot of debate on whether coffee is healthy or unhealthy, most research points to the former. On top of that, caffeine boosts our productivity. According to one review paper, it deepens our ability to focus, increases our mental performance, and helps us persevere – especially with long and tedious tasks. 

However, timing matters. When you consume caffeine can make or break your energy levels throughout the day. In last week’s post, you learned that melatonin, the “hormone of darkness”, makes you drowsy and eventually lets you fall asleep in the evening. As it turns out, there is a second chemical with a similar job called adenosine. This neurotransmitter drives your sleep pressure and increases with the time you've spent awake. As it effectively tells your brain when to be tired, you can also think about adenosine as the “sleepiness chemical”.

Unlike melatonin, adenosine doesn’t get triggered by light, but builds up from the moment you wake up in the morning and throughout the day. It’s similar to an hourglass that gets turned around when we sleep. In the morning, when most of the sand is in the upper chamber of this hourglass, your sleep pressure is low. By the evening, when most of the sand (ideally) has made its way into the lower chamber, your sleep pressure is high.

This brings us back to caffeine. That substance, it turns out, makes us alert ​​by occupying the adenosine receptors in the brain. In doing so, caffeine prevents these receptors from absorbing the adenosine that’s floating around. In other words, caffeine prevents adenosine from communicating its sleepiness signal, and thus tricks our brain into feeling alert and awake – even if there is a high level of adenosine that would otherwise make us sleepy.

Here’s the problem: While caffeine occupies the adenosine receptors in your brain, the “sleepiness chemical” continues to build up. Once the caffeine is metabolized, you'll experience a massive surge in sleepiness, driven by the release of all of that extra adenosine. When we start ingesting caffeine right after waking up, we thus experience a steep decline in mental energy in the afternoon. This “caffeine crash” adds to the natural trough in alertness that most of us naturally experience around 3 pm. 

As with cortisol and melatonin, the dance between caffeine and adenosine can make or break our mental energy.

The magic of delaying caffeine

Fortunately, there's a simple remedy that I first learned about from Andrew Huberman: By avoiding caffeine in the first 90 minutes after waking, you’ll let your body wake up naturally from the healthy spike in the "waking-up hormone" cortisol (if you got sufficient light into your eyes before 10 am).

Then, later in the morning, when cortisol levels are lower, consuming caffeine can give you a nice boost in mental energy without setting you up for an afternoon crash. And with the delayed caffeine intake, you'll finally get sleepy in the evening instead of the afternoon. 

Unlike in the afternoon, high levels of adenosine are precisely what we need in the evening for our mental energy to come down eventually. Yet, having caffeine in the late afternoon or evening will take away your sleep pressure exactly when you need it most. Since caffeine has a half-life of 5 to 7 hours, avoid it at least 8 hours before bed. 

On top of timing, quantity matters. According to the Mayo Clinic, up to 400 mg of caffeine a day is safe for most healthy adults. That's the equivalent of 2 to 4 cups of coffee, depending on the size and strength. Greater amounts can make you feel more anxious, and your performance might even become impaired.

Instead of caffeine, resort to water early in the day

Early in the morning, have plenty of water instead of caffeine. Why? Not getting enough water causes fatigue and even anxiety. Being well-hydrated, conversely, makes us alert. As we typically don’t drink at night, having a glass of water right after getting up will provide you with what you need to get going early in the day.

Chances are you should be drinking more water each day than you currently are. According to the Mayo Clinic, the adequate daily intake is 2.7 liters for women and 3.7 liters for men. Since we get about 20% of our water from food, we should aim for drinking 2 and 3 liters, respectively. And as with caffeine, timing matters: For a better night’s sleep, try to drink most of your water in the first 10 hours of the day.

If you can't go without caffeine in the early morning or late afternoon, decaf coffee is an excellent alternative. Yet, choose a product that actually lives up to its label: According to sleep expert Matthew Walker, some varieties contain 15 to 30 percent of the dose found in a regular cup of coffee. So do a quick Google search and pick a variety that’s really decaf. If you’re based in Germany, try out OHNE. It’s both really decaf and really tasty.

In short, here’s how to optimize your caffeine and water intake for alertness during the day and drowsiness at night:

1) Wait 90 minutes after waking up before having your first caffeine. Limit your intake to 400mg per day. And avoid it at least 8 hours before bed. 

2) Drink plenty of water after waking up to get a head start to the day. Women should go for 2 liters a day, men for 3 liters. Have most of it in the first 10 hours of the day.

3) If you can’t do without your coffee early in the morning or late in the afternoon, go for decaf coffee instead.

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Until next week,
Christian