The next time you’re reaching for your morning cup of coffee or brewing your afternoon tea, consider this: the caffeine you’re about to consume is one of the most studied food ingredients in the world. Over the years, researchers have delved into just about every aspect of caffeine, from how it affects mental alertness and athletic performance to whether or not there’s a chemical difference between synthetic and naturally occurring caffeine (spoiler alert: there isn’t).
Naturally, a great deal of the research on caffeine focuses on the impact it has on health and the body. All this information helps agencies like the FDA—the agency responsible for regulating the use of added caffeine in foods, beverages, and other consumable products—make sure that caffeine is used safely and responsibly by food manufacturers. But the data also makes for fascinating reading in its own right. Check out the following interesting facts, courtesy of scientific research, about how caffeine works in your body.
Caffeine takes 15-45 minutes to be absorbed by your body.
Caffeine is an amphiphilic substance, which means that it has the ability to move freely through all the body’s membranes. As a result, caffeine can pass easily through the blood-brain barrier—the very selective, semi-permeable border that protects the brain and only allows certain substances through. Caffeine starts chemically affecting your brain within 15 to 45 minutes of consumption. So if you’re still feeling a little dozy after your first coffee of the morning, try waiting a little longer, till the caffeine is fully absorbed, before reaching for your second cup.
Caffeine doesn’t work faster if you drink it quickly.
The absorption rate for caffeine, as described above, appears to remain consistent regardless of how quickly you might drink a caffeinated beverage, and also regardless of other factors like beverage temperature. What this means is that drinking two cups of coffee in quick succession, rather than spacing them out, is not going to lead to faster absorption or have any other meaningful impact on your caffeine intake. When it comes to caffeine intake, quantity, not consumption rate, is the important factor to monitor.
Caffeine is a doppelganger.
Caffeine molecules resemble another molecule called adenosine, which helps you fall asleep by calming brain activity, dilating blood vessels, and encouraging relaxation. When you drink a cup of coffee, caffeine and adenosine molecules compete to bind to receptors in your brain: when caffeine wins the fight by taking up receptor space that would otherwise be occupied by adenosine, the adenosine is prevented from doing its job. As a result, your blood vessels constrict, your nerve cells fire faster, and you typically feel more alert and wakeful.
Caffeine has a relatively long (and variable) half-life.
In a nutritional context, “half-life” refers to how long it takes for half the original dose of a molecule to be eliminated from the body. Typically, caffeine has a half-life between five and seven hours, but even wider ranges have been reported, from as few as 2.3 to as much as 9.9 hours. All kinds of factors, from age and genetics to lifestyle choices, can influence the half-life of caffeine. From an individual perspective, understanding half-life is helpful because it can give you a better idea of when you might want to reach for your last coffee or soda of the day. For example, if you drink a cup of coffee containing about 100 mg of caffeine at 4:00 p.m., 50 mg of caffeine may still be present in your body when you’re thinking about getting ready for bed at 10:00 p.m.
When it comes to caffeine in your body, the liver plays a major role.
The organ that metabolizes caffeine in your body—after it’s done the job of perking you up, of course—is the liver. The hardworking liver breaks down caffeine into three major metabolites, which are themselves active ingredients: the majority of the caffeine is broken down into paraxanthine (84%), and the rest into theobromine (12%) and theophylline (4%). After this metabolic processing, anything remaining is excreted by the kidneys into your urine.
Caffeine functioning is greatly impacted by lifestyle choices.
How is it possible that one energy drink after lunch will keep you awake till the small hours of the morning, while your friend who enjoys two espressos after dinner never has any trouble falling asleep? It’s all down to a number of lifestyle factors that can have a major influence on how caffeine affects different people. In particular, big choices like smoking and diet can strongly impact the metabolism of caffeine: did you know, for example, that smokers can metabolize caffeine up to twice as fast as non-smokers? In addition, when you take other factors like age and genetics into account, it’s easy to see that a one-size-fits-all approach when it comes to caffeine consumption recommendations presents a serious challenge.