How Things Work: Caffeine

How is it that Red Bull gives you wings? And even though coffee can give us bad breath and yellow teeth, it seems to be the solution to all our late nights. According to statistics on, up to 90 percent of Americans consume caffeine each day, in the form of coffee, soda, or tea. So, how does caffeine work?
First, let?s discuss how we fall asleep in the first place. The brain creates a sleep-inducing factor called adenosine. During the day, adenosine accumulates in the brain. It binds to adenosine receptors and causes nerve cell activity to slow down, and blood vessels to dilate, which gets more oxygen to the brain. In this way, adenosine causes fatigue, drowsiness, and sleep.
When caffeine enters the system, it alters the chemical makeup of the brain. Acting as a competitive inhibitor, caffeine mimics adenosine and binds to all the adenosine receptors in the brain. As a result, adenosine loses its ability to make our eyes droop.
So what happens? Your brain no longer detects the presence of adenosine, so the nervous system cannot be regulated. If adenosine were detected, brain activity would slow down. Instead, the pituitary gland begins to pump out signals that cause the adrenal glands to release adrenaline, the ?fight or flight? hormone. Adrenaline brings your body to an alert state. Higher levels of adrenaline result in an increased heart rate, dilated pupils, increased blood sugar released from the liver for energy, increased respiration, and blood vessel contraction. Your hands get cold because of blood vessel contraction, especially since there is no adenosine to open them.
Excessive caffeine intake (say, 10 cups of coffee per day) results in difficulty sleeping, jitteriness, and anxiety. If you keep drinking coffee, bodily adrenaline levels remain high. This means your body is in a constant state of alert.
On the other hand, caffeine can be beneficial for some health problems. For example, headache medicines contain caffeine because it will close blood vessels and relieve the headache.
Caffeine also increases the levels of dopamine in your brain. Dopamine is a neurotransmitter that stimulates the part of the brain that controls pleasure; it enhances your mood and state of well-being. Amphetamines, such as heroin and cocaine, also control dopamine levels by slowing down the rate of dopamine recycling.
The effects of caffeine are much less significant than those of amphetamines, but they are similar.
Caffeine causes dehydration because it inhibits the antidiuretic hormone (ADH). ADH is involved in fluid storage in the body; it causes the kidneys to reabsorb water. When ADH is not present, there is decreased water reabsorption in the kidneys, which, in turn, increases the need to urinate.
Sustained, daily caffeine intake increases the body?s tolerance. Conversely, without caffeine, the body becomes oversensitive to adenosine. This causes blood pressure to drop, resulting in headaches and dizziness. Other withdrawal symptoms include irritability, restlessness, and difficulty concentrating.
Caffeine has long-term negative effects on sleep. Continuous adenosine blocking from the brain?s adenosine receptors will prevent the body from entering the deepest part of sleep.
The short-term effects of caffeine are advantageous if you want to stay awake. It takes effect in as little as 15 minutes and will stay in the body for about six hours. Caffeine blocks adenosine reception so you don?t get sleepy. It also gives the body an adrenaline boost and increases dopamine levels, which makes you feel good.
Caffeine does have some positive effects, but keep in mind that the long-term effects can be damaging.