Understanding Caffeine: What Really Happens When You Drink Coffee

Whether a double espresso or a cold glass of soda, you’ve got lots of choices when it comes to getting your caffeine fix. And however you take it, this extra boost gets many of us through the day. 

Understanding how caffeine works can make you more aware of its effect on your energy levels and overall health. What really happens when caffeine enters the body? How long does it last, and can it influence sleep patterns?

What is Caffeine and Why Do We Drink it?

Caffeine is a stimulant with a long history of both consumption and controversy. While the most popular source of caffeine is coffee, followed by soft drinks, it can also be found in energy drinks, yerba mate, brewed tea, chocolate and some over-the-counter drugs, says registered dietitian and sports nutritionist Alina Petre

Ingested by millions of people across the globe for hundreds of years, caffeine is the world’s most popular habit-forming, mood-altering substance, says documentary filmmaker and author T.R. Reid at National Geographic. “An alkaloid that occurs naturally in the leaves, seeds, and fruit of tea, coffee, cacao, kola trees, and more than 60 other plants, this ancient wonder drug had been prescribed for human use as far back as the sixth century B.C.,” he explains.

Despite its popularity, many people don’t realize that caffeine is actually a psychoactive drug, according to reporters Kevin Loria and Erin Brodwin at Business Insider. It changes both the way we feel and the way we interact with the world around us. Being classified as a drug doesn’t mean caffeine is inherently bad — but what exactly does it do to us when we drink it?

How Does Caffeine Affect the Body?

We can all agree that caffeine makes us feel more alert, but why?

Caffeine gives us energy because the stimulant blocks adenosine, the molecule in our brain responsible for fatigue. Adenosine increases throughout the day and decreases during sleep, explain AsapSCIENCE cofounders Mitchell Moffit and Gregory Brown

Caffeine starts blocking adenosine just fifteen minutes after it’s absorbed by the bloodstream, health writer Jessica Migala says. After this peak, the liver takes over in eliminating the drug. A healthy liver is the reason the effects of caffeine fade. Consumed occasionally, your body likely won’t build up a tolerance to caffeine and the same amount will continue to block adenosine and cause alertness. 

The more caffeine we consume, however, the more of it we need to get a boost of energy, writes Gina Riggio. “Caffeine's stimulant effect on the central nervous system is dose-dependent; the more caffeine consumed, the stronger the stimulant effect.”

Blocking adenosine causes the adrenal glands to secrete adrenaline — the chemical associated with our flight or fight response. A surge of adrenaline leads to increased heart rate, body temperature, blood pressure, blood sugar and dopamine. Because of its stimulant effect on the central nervous system, caffeine is often used in over-the-counter drugs and pain relievers to treat or manage common ailments, such as headaches, migraines and drowsiness, explain Ann Pietrangelo and Kristeen Cherney at Healthline.

How Long Do the Effects of Caffeine Last?

How caffeine affects the body depends on who’s drinking it, and how much they’re drinking. According to the FDA, 400 milligrams of coffee a day (that’s four or five cups) is generally not associated with negative effects.

Still, people process caffeine at slightly different rates depending on metabolism, weight, age and a number of other factors. Being pregnant, taking certain medications or having high blood pressure can also play a role in how caffeine affects you and whether or not it’s safe to consume.

“People have different reactions to caffeine. Some can drink six cups of coffee a day and feel fine, others need to switch to decaf or herbal tea by noon or they'll be up all night,” says health writer Candy Sagon.

Caffeine stays in your system for several hours. According to the National Sleep Foundation, it takes roughly six hours to eliminate one half of the caffeine consumed. This is why it’s often advised not to drink caffeine late in the afternoon, as it can affect sleep quality, causing a cycle of additional daytime drowsiness and addiction to caffeine.

A study was held to determine exactly how the stimulant keeps us awake at night. Conducted by the Sleep Disorders & Research Center at Henry Ford Hospital and Wayne State College of Medicine, the findings were surprising. 

Participants drank the equivalent of four cups of coffee throughout the day at three separate times. Their sleeping and waking times were measured, as well as their quality of sleep at night, writes productivity coach Melissa Chu. As expected, those who consumed caffeine up to three hours before bedtime reported significant sleep disruption. Interestingly, participants who stopped consuming caffeine six hours before bedtime reported that their sleep wasn’t disrupted — but the sleep monitor showed that it was.

“The perception of caffeine’s effect on the body was not a direct measure of how it affected sleep. In other words, participants might not have felt the caffeine in their body, but it still affected their sleep quality for the worse.” 

Optimizing your caffeine intake can ensure that you get the maximum benefits of this stimulant without disrupting your sleep. Allow your body to wake up naturally before sipping your cup of coffee to fully enjoy the impact of caffeine, write Jake Knapp and John Zeratsky, authors of “Make Time: How to Focus on What Matters Every Day.” Caffeine can’t compete with cortisol, the body’s main stress hormone that controls your wake and sleep cycles, so it’s best to wait until cortisol levels have dropped.

“For most folks, cortisol is highest between 8 a.m. and 9 a.m., so for ideal morning energy, experiment with having that first cup of coffee at 9:30 a.m.,” they advise.

Inc contributing editor Geoffrey James agrees that coffee shouldn’t be consumed first thing in the morning for people who want to maximize its energy-boosting effects. In contrast, James says that it’s best to drink coffee (or other caffeine-rich drinks) between nine and noon, for people who wake around 6:30 a.m. 

This is because cortisol levels are highest between eight and nine in the morning and between noon and one in the afternoon. While cortisol also peaks in the evening, drinking before noon is best, James adds. “Caffeine remains in your system for up to 12 hours and can help create insomnia, a huge source of stress and a major health hazard.”

Properly timing your caffeine consumption and understanding its effects on your body can ensure you receive its maximum benefits without the adverse effects.

Images by: rawpixel, nappy, Lukas

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