This Is Your Body on Caffeine

Many of us down caffeinated drinks — coffee, tea, soda, or energy drinks — to wake ourselves up in the morning, stay more alert in the evening, or bolster our mood. But the caffeine you’re imbibing may not be working the way you think it is. Here’s what happens when you down a caffeinated drink and your body gets hit with the jolt.

Within Seconds
Caffeine (like alcohol) is one of the few chemicals that is soluble in both water and fat, so it is absorbed quickly through the stomach lining and small intestine. From there, it penetrates your cells and is distributed throughout your body, appearing later in all sorts of bodily fluids like saliva, semen, breast milk, and amniotic fluid.

10 Minutes
You begin to feel more alert. Caffeine’s chemical makeup is nearly identical to adenosine, a neurotransmitter that signals your brain to slow down when you’re tired. Caffeine attaches to adenosine receptors and blocks it from putting on the brakes. This allows your body’s natural stimulants, like endorphins and glutamate, to flow unhindered.

30 to 45 Minutes
Caffeine reaches its peak as it slows your ability to absorb dopamine. This neurotransmitter helps you feel focused, motivated, and energized — and it can also cause heart palpitations, breathlessness, and feelings of fear. As the caffeine blocks the chill-out adenosine receptors in your kidneys and colon, the urge to go to the bathroom increases.

1 to 5 Hours
Your body realizes it’s being drugged and releases adrenaline in self-defense. This increases your heart rate and blood pressure, causes some blood vessels to constrict, and tells your liver to attack the caffeine. Liver enzymes then create the metabolites theobromine, theophylline, and paraxanthine — each corresponding to a different kind of high, from alertness to jitters.

5 to 6 Hours
The buzz subsides as your liver breaks down the caffeine. But the timing varies by individual: Smokers typically process the caffeine in three hours (it’s thought the process is sped up by the chemicals in cigarette smoke). Women using contraceptives may require 10 to 12 hours (the scientific explanation for this is as yet unclear).

12 Hours
Withdrawal kicks in. As caffeine’s chemical roller-coaster ride comes to a close, its effect on your neurovascular system wears off. Your blood vessels relax. As your body attempts to rebalance itself, you may feel a wave of fatigue or the onset of a headache.

How Much Caffeine Is In There?

Sources: USDA’s National Nutrient Database for Standard Reference and Center for Science in the Public Interest.