Caffeine: What It Is and What It Does

Ever wonder why it feels like you can’t get through the day without your morning cup of coffee? Or why you turn to that mug of tea or piece of chocolate for an afternoon pick-me-up? Each time you enjoy your favorite caffeinated treats, you’re ingesting one of the most commonly used stimulants in the world.

What exactly is caffeine, and what are its possible benefits and risks? Registered dietitian Beth Czerwony, RD, LD, delves into the science.

What is caffeine?

Caffeine is a type of drug called a stimulant, meaning it increases chemicals in your brain called neurotransmitters. This excites or motivates your central nervous system, the processing center that regulates everything your body does.

A little bit of caffeine can help you feel more alert, awake and focused. But too much of it can cause side effects, from jitteriness and stomach issues to heart palpitations and beyond.

Caffeine occurs naturally in certain plants:

• Coffee beans
• Cacao beans (what chocolate is made from)
• Tea leaves
• Kola nuts
• Yerba mate
• Guarana berries

It’s also added to various products, like soda, energy drinks, pre-workout powder and more.

Uses and benefits

A low to moderate amount of caffeine — 37.5 to 400 milligrams (mg) per day — can boost your mood, raise your energy levels, and improve your physical and mental performance.

• Alertness. Caffeine helps you feel more awake by blocking the effects of adenosine, a neurotransmitter that makes you feel tired. Even in people with partial sleep deprivation, 300 mg of caffeine has been found to significantly improve daytime alertness.
• Mood. It’s not in your head: That latte really does perk you up. Blocking adenosine can cause an increase in dopamine and norepinephrine activity, two neurotransmitters that are associated with better mood.
• Focus. Dopamine and norepinephrine are also associated with better focus and attention. Studies have explored how caffeine may help adults with attention-deficit/hyperactivity disorder (ADHD) improve their concentration and attention, especially when it comes to doing repetitive tasks.
• Physical performance. There’s a reason your pre-workout powder contains caffeine: In moderate doses, it’s shown to help improve athletic endurance.
• Headache relief. Some pain relievers contain caffeine, which can speed up the rate at which your body absorbs the medication and help you feel better faster.

Some studies propose other health benefits of caffeine, too. It continues to be studied for possible positive effects on inflammation, Type 2 diabetes and the lining of the heart and blood vessels.

In fact, some research suggests that caffeine might help you live longer! Various studies have shown that coffee drinkers in particular have lower rates of cancer and chronic diseases than people who don’t drink coffee. Long-term caffeine consumption has also been associated with preventing or lowering the risk of:

• Alzheimer’s disease
• General cognitive decline
• Stroke
• Parkinson’s disease

Risks and side effects of caffeine

Even though you may not think of your cozy daily cuppa as anything sinister, caffeine is still a drug. Consuming as little as 300 mg of caffeine (or roughly four cups of coffee) can increase your risk of unpleasant side effects like:

• Anxiety
• Digestive issues, like upset stomach or diarrhea
• Dizziness
• Heart palpitations
• Heartburn
• An increase in blood pressure
• Irritability and agitation
• Jitteriness
• Nausea
• Trouble sleeping

Consuming too much can lead to caffeine overdose, a serious condition that brings more severe neurological (brain) and cardiac (heart) effects. It can cause arrhythmias (heart rhythm disturbances), seizures and even death.

“Because caffeine is a stimulant, it’s important to understand your sensitivity to it and consider your overall health so that you can recognize your limits,” Czerwony says.

Is caffeine good or bad for you?

Caffeine is generally considered safe and is typically OK to include in your daily diet. But as is so often the case, too much of a good thing can quickly become a bad thing — especially if you’re extra sensitive to its effects.

“If caffeine gives you the jitters or you find you’re becoming too dependent on it, you should consider cutting back,” Czerwony advises. “And if you experience symptoms other than the occasional jitters, it’s best to seek medical care.”

If high-caffeine options like coffee don’t seem to agree with you, look for decaf or “low-caf” options, like tea, mushroom coffee or other coffee alternatives.

Caffeine also isn’t safe for everyone, including kids under 12. Ask your healthcare provider about whether there’s a safe amount for you if you:

• Take anti-anxiety medications
• Are pregnant or breastfeeding
• Have heart disease or high blood pressure

But if you’re otherwise healthy, caffeine is safe in moderation. Healthy adults shouldn’t consume more than 400 mg of caffeine per day, and teens should stick to less than 100 mg per day. And Czerwony shares an important reminder: Caffeine is found in more than just coffee!

“When we talk about caffeine, most people’s minds turn to coffee,” she says, “but keep in mind that other items have caffeine in them, too, and it has a cumulative effect. If you have two cups of coffee in the morning, an energy drink in the afternoon and a cup of tea with a piece of chocolate after dinner, it all adds up!”