Why Does Coffee Wake You Up?

Author: | Posted in Science, Trivia 11 Comments

coffee_awakeInstant, with cream, with sugar, percolated, pressed, or just plain black – coffee is one of the most popular drinks in the world. Millions of people are involved in the production of the hot black drink, and millions more drink it. The US even celebrates Coffee Day on September 29. We all know coffee will perk us up. But why? We’re going to find out just why the coffee bean does what it does.

One shot or two?

The active ingredient in coffee is primarily caffeine – it’s what gives coffee its kick. The levels of caffeine in a cup of coffee will vary depending on:

  • The size of the cup
  • The roast (the darker the roast, the lower the caffeine level)
  • The brew method (press, drip, percolator, espresso, dirty sock)
  • How fast you drink it (one cup drunk over an hour will have less effect than one cup drunk in 30 seconds: chug, chug, chug!)

Caffeine is also present in tea, cola, as well as some foods including chocolate. However, the levels tend to be higher in coffee than in most other consumables: coffee can have more than double the caffeine content compared to tea.

From your mug to your brain

In order to understand what caffeine does to our body and brains, we’ll need to know what it means to be sleepy. The sensation of sleepiness mostly comes from a brain chemical known as adenosine. As mentioned in a previous article, Why Do We Sleep, adenosine is a created as a by-product of cellular activity in your body, like carbon dioxide. Adenosine isn’t just a waste product though – it ensures that the brain is not overloaded with stress chemicals and makes sure that we get the rest the our body needs. Removing adenosine from the equation doesn’t remove the need for sleep, it just silences its loudest proponent.

coffeebeansAlso unlike carbon dioxide, adenosine is not flushed from the body throughout the day. Instead, adenosine builds up in your system. As the day goes on, your adenosine levels build and you start feeling sleepy. When you sleep, adenosine is finally removed from your system and the cycle repeats. As we can all relate, sometimes you don’t get enough sleep – so your adenosine levels are not adequately lowered. This makes you start your day feeling drowsy. So you reach for a cup of coffee.

The effect of coffee and its caffeine is to block the effects of adenosine on your brain. It also increases the flow of stimulation chemicals, including acetylcholine, epinephrine, dopamine, serotonin, glutamate, norepinephrine, cortisol, and endorphins.

Caffeine is able to have such a profound effect because it is both water-soluble and fat-soluble. This allows it to cross easily from the blood stream straight into your brain. Once there, caffeine can get to work. The molecular structure of caffeine is similar to that of adenosine – they essentially have the same shape. Because of this, once the caffeine is in your brain, it can bond with adenosine receptors. Since the caffeine molecules are taking up this space, there is no room for adenosine to bond, and the adenosine in your system is therefore not able to make you sleepy.

Along with this, caffeine also speeds up the release of energy from fat cells and changes the way your brain perceives neuron activation. This gives some of the characteristic pep of coffee, where you have more energy and can expend more effort.

The effect doesn’t stop there. When the food and drink you consume hits your digestive system it undergoes a lot of changes. It’s broken down into other parts, and these parts can have additional effects on your body. The caffeine in coffee is broken down into additional parts known as paraxanthine, theobromine, and theophylline. These have the added effects of:

  • Releasing energy into the blood stream.
  • Increasing oxygen flow to brain and muscles
  • Increasing heart rate

But that’s not all

With an ever hungry sweet tooth, coffee doesn’t just mean coffee. Coffee may also include cream, sugar, cocoa, or any number of flavorings and additives. How much you put in your coffee significantly increases the level of stimulation you receive, particularly from the sugar content.

The same is doubly-true for store bought coffee. A venti (large) Starbucks Caramel Apple Spice contains 83 grams of sugar. A venti Java Chip has 84 grams of sugar. The venti Green Tea Frappuccino packs 87 grams of the sweet stuff. See more at the Starbucks nutritional info page.

Forget caffeine – the sugars in these drinks are sure to wake you up, and keep you up. Dr Ian Campbell, head of the National Obesity Forum, is quoted as describing these kinds of drinks as a “sugar bomb.” Taken late in the day, the collateral damage for this sugar bomb is your sleep. Kaboom.

Correction: Sugar does not contribute to wakefulness! It may add to your waistline, but won’t keep you up at night. See our article on sugar and sleep to find out more.

Coffee before bed

Since the effects of coffee directly affect your brain on a chemical level, and continue to do so even after the caffeine is digested, it stays in your system for a long time. How long you stay perked up by coffee depends on a number of factors, such as:

  • Age
  • Liver function
  • Medications or drugs
  • Pregnancy and strong hormonal patterns
  • Smoking
  • How much coffee you regularly drink

Each individual’s unique biology also affects how their body will deal with coffee and caffeine. For some, a single sip will send them bouncing off the walls – others will pound down lattes as a night cap.

Generally speaking, to ensure that coffee doesn’t keep us from sleep, we should avoid coffee four to six hours before bed. That means no after dinner coffee, and maybe even no late-afternoon coffee time.

Coffee withdrawal?

For people who drink a lot of coffee, there may be less to their morning cup than they think. Researchers at the University of Bristol conducted a study of low/no caffeine consumers and medium/high caffeine consumers. Each group was tested in the morning, and given either a dose of caffeine, or a placebo. It should come as no surprise that the medium/high caffeine consumers that received a placebo (no caffeine) reported lower levels of alertness and incidences of headache.

However, researchers found that even after the medium/high consumers had caffeine, they had no higher levels of alertness than the low consumers that received just a placebo. Their conclusion was that, for regular high consumers of caffeine, their morning cup merely brings them back up to normal. Their morning fog is caused not by tiredness, but by caffeine withdrawal.

Unfortunately, lacking a subscription to Neuropsychopharmacology, I don’t have access to all the details. I would wonder if the study gave medium and high users enough caffeine to adequately represent their actual real world consumption. Was a dose of caffeine equivalent to one cup? It’s been my experience that most coffee drinkers have more than one cup, and the effects on alertness may be more pronounced with increased dosage. One cup may only be enough to get high users back to normal, but beyond that is perky-town.

Either way, the study is an excellent reminder about how we can develop tolerances, and withdrawals, from this ubiquitous, delicious, but sometimes mean, bean.

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