How Does Caffeine Affect the Body?

It is the active ingredient in your daily cup of coffee. It provides the energy boost you get from teas, soda, chocolate, and energy drinks. It is the world’s most popular drug: caffeine.

Caffeine seems like a wonder substance—it’s naturally occurring, easy to consume in many forms, has minimal side effects, and lasts for hours. 

Students, athletes, travelers, and busy people rely on caffeine to fight fatigue. Caffeine is as popular as it is effective – 80% to 90% of American adults report regularly consuming caffeine while 75% of people do so daily.

But boosting energy is not all caffeine does. It also increases nerve activity and stimulates the body in numerous ways. We have the scoop!

Caffeine’s Effects on the Body

When you consume caffeine, it’s rapidly absorbed into your bloodstream affecting multiple systems. And within 15 minutes, you can begin to feel the effects. Caffeine easily passes through the blood-brain barrier, directly stimulating the brain as well as the respiratory, central nervous, renal, and cardiovascular systems. 

The primary way caffeine affects the body is by blocking the action of a chemical called phosphodiesterase (PDE), preventing it from breaking down into cyclic adenosine monophosphate (cAMP). What’s important to know is that cAMP releases epinephrine into your system that triggers a fight or flight response, stimulating the body in the following ways:

• In the central nervous system, caffeine elevates dopamine and norepinephrine neurotransmitters that stimulate the brain. This increases alertness, focus, adrenaline, and cortisol.  

• In the respiratory system, caffeine relaxes the bronchi muscles to make breathing easier.

• In the renal system, caffeine increases blood flow and urination.

• In the cardiovascular system, caffeine constricts blood vessels and elevates blood pressure.

Because caffeine affects your body’s alertness, it has a lingering effect on your system that can last up to six hours. This is because the half-life of caffeine for adults is roughly five hours. For example, if you consume 10 milligrams of caffeine, five hours later you would have five milligrams still in your system. This lingering dose continues to give you sustained energy and alertness.

Medical Uses for Caffeine

While caffeine is commonly used to increase mental focus and physical energy, it’s also used as a medical treatment for:

• Hair Loss: Caffeine is topically applied on the scalp to increase blood circulation, providing nutrients and oxygen to the hair follicles for maximum health.

• Headaches: Caffeine is an active ingredient in over-the-counter headache medicines as it opens blood vessels in the brain to combat migraines caused by constricted vessels (vasodilation).

• Asthma and Apnea: Caffeine injections open the respiratory system to improve airflow and breathing.

The Side Effects of Caffeine

While caffeine’s perks and euphoric boost make it a go-to drug for many people, it does have side effects.

The most innocuous is “caffeine jitters” in which we experience shaky, diminished coordination as caffeine increases nerve activity.

Caffeine can also keep us awake longer than intended due to how long it remains in the body. To prevent this, avoid consuming caffeine at least three hours before bedtime.

In pregnant individuals, caffeine crosses the placenta to the fetus and is slowly metabolized. Therefore, limited caffeine is recommended during pregnancy.

While safe in daily amounts, it’s important to recognize that caffeine is a drug. At high enough doses, it can even be fatal. The Food and Drug Administration (FDA) considers 10,000 to 14,000 milligrams of caffeine to be potentially deadly for an adult (that’s equal to 100 cups of coffee consumed in one sitting).

Harmful effects appear even at a lower 1,200-milligram dose, which could result in:

• An accelerated heart heart
• Ventricular arrhythmia
• Seizures

Keep in mind these estimates are for healthy adults. People who have heart conditions or are pregnant, as well as children, have lower tolerance levels for caffeine. 

The Long-term Effects of Caffeine Use

While it is possible to overdose on caffeine, fortunately, most of us don’t consume enough every day to experience long-term effects. The FDA recommends limiting your caffeine consumption to less than 400 milligrams a day, which is easy since most people consume less than 300 milligrams daily.

If you’re consuming more than 1,000 milligrams a day, you could experience:

• Fertility issues
• Osteoporosis
• Heartburn
• Increased anxiety
• Changes in bowel habits

Concerned about your intake? Refer to this chart of common caffeine sources and amounts to calculate your daily intake.

Caffeine Source	Caffeine in Milligrams (mg)
Coffee 8 oz. serving	95 mg
Espresso shot at Starbucks	75 mg
Tea 8 oz. serving	45 mg
Average energy drink 8 oz. serving	85 mg
5-hour energy shot	200 mg
Dark chocolate 3.5 oz. bar	80 mg
Caffeine pills	100 – 200 mg per dose

Keep in mind that serving sizes have increased over the years. It’s important to multiply these amounts based on your actual consumption.

Caffeine Withdrawals

Caffeine is highly addictive. Therefore, quitting cold turkey can create withdrawal symptoms, including:

• Intense headaches
• Fatigue
• Irritability
• Difficulty concentrating
• Flu-like symptoms (nausea, vomiting, and muscle pain)

These symptoms can last up to a week. It’s recommended to wean yourself off caffeine slowly. First, scale back on the number of caffeinated drinks you consume every day and reduce your intake over time. Second, replace your highly caffeinated drinks with less concentrated ones, such as black or green tea. Third, drink lots of water. Hydrating provides an energy boost to make caffeine unnecessary.

Be mindful that caffeine is included in numerous products that we may not even be aware of, such as:

• Sweetened drinks
• Sweetened coffee and tea
• Carbonated water
• Energy bars
• Chocolate
• Certain medications

A Better Way

Now that we have a clearer understanding of how caffeine affects the body, we can change our relationship with it.

We don’t need as much caffeine as we think. For many people, a 50-milligram dose can be just as effective as higher doses. Moreover, we learned it takes at least 15 minutes to begin to feel the effects of caffeine. So, be sure to slow your consumption and wait to feel the energy boost before drinking more.

Furthermore, due to the way caffeine is metabolized, you’ll experience a sustained boost if you spread your caffeine consumption out during the day rather than taking one hefty dose to jumpstart your day. For instance, instead of drinking a double shot in the morning, have one in the morning and one in the afternoon as your energy wanes. This combined with short 15 to 20-minute power naps increases your alertness.

But caffeine isn’t the only way to boost your energy. Often, drowsiness is the first sign of dehydration, therefore ensuring that you’re well-hydrated is key. Moreover, take vitamin B and taurine every day. Vitamin B converts the nutrients in your food into energy while taurine improves your circulation and physical performance to keep you powered naturally.