​​We all know that sleepy feeling, whether it's from an early morning trip to the airport, a late-night work session or that midday slump. For many of us, one thing will pull us through—a jolt of caffeine. Taken as coffee, tea or an energy drink, a dose of caffeine can wake you up and get you moving.

After those first few sips, you feel more awake and alert. But have you ever stopped to think about what caffeine is and how it affects your body? There's a lot to consider before you pour your next morning cup of joe or settle into your nightly post-dinner tea.

Benjamin P. Smith, MD, a family medicine physician with The Christ Hospital Physicians, shares the good and bad about your daily liquid pick-me-up.

What is caffeine?

Caffeine is a naturally occurring stimulant commonly found in coffee beans, tea leaves and cocoa beans. It boosts your brain and nervous system activity by blocking adenosine, a neurochemical that promotes sleepiness.

Roughly the same size and shape, caffeine molecules can easily impersonate adenosine. Dr. Smith says it fills in your adenosine receptors—proteins on your cells that respond to adenosine's signal. But caffeine doesn't activate those receptors.

“When adenosine connects with its receptors, it makes us feel tired. Adenosine is constantly working in our bodies at some level, so we always feel a little bit tired," Dr. Smith says. “By drinking caffeine, we can block adenosine from hitting those receptors. So, we feel more energetic and have more focus."

When caffeine occupies your adenosine receptors, the neurotransmitters dopamine and glutamate—your brain's natural stimulants—can more easily trigger your energy burst.

Caffeine's impact: The good and bad

Nearly all American adults drink caffeinated beverages with 85% consuming 135 milligrams (mg) of caffeine daily. That's about 12 ounces of coffee. If you're a daily drinker, you should know how the caffeine affects your body. Dr. Smith says moderate caffeine consumption (roughly four cups of coffee per day) is enough to impact you in a variety of ways.

Positive benefits

Regular caffeine consumption can offer several positive effects, including:

• Better cognitive function
  
• Greater alertness
• Greater focus
• Headache relief (caffeine constricts your blood vessels, relieving pain and pressure)
• Improved mood
• Increased mental and physical endurance

Negative impacts

But drinking caffeinated beverages can also trigger unwanted side effects:

• Acid reflux
  
• Anxiety and jitteriness
• Caffeine dependence and withdrawal
• Disrupted sleep and insomnia
• Frequent urination
• Heart palpitations and increased heart rate
• High blood pressure
• Upset stomach

A personalized response

Caffeine affects everyone differently, so you need to pay attention to how your body responds.

“Several factors contribute to how much caffeine we're able to enjoy," Dr. Smith says. “Everyone has an individual response to caffeine. Keep track of how much you're consuming and when you're drinking it."

Your genetics play a big role in your caffeine sensitivity and dependence. For example, a genetic variation of a liver enzyme can slow down how quickly you process caffeine. As a result, you'll feel more jittery and get less sleep. These changes can also increase high blood pressure and heart attack risk. In addition, researchers have identified two other genes directly linked to how much you crave caffeine.

What the research says

There's no shortage of research about the health effects of caffeine. Some studies indicate caffeine protects against Alzheimer's disease and Parkinson's disease. Other studies show caffeine can reduce your risk for coronary heart disease, stroke, diabetes and kidney disease.

These results are encouraging. But Dr. Smith says there's more to the story.

“Many of these studies are based on consuming copious amounts of caffeine. Sometimes, it's up to 10 cups of coffee a day. Almost no one is consuming that much," he said. “The risk improvement is also frequently very small—sometimes only a percentage or two. So, you must decide for yourself if it makes sense to consume more caffeine for the modest health benefit."

Dr. Smith pointed out that many health benefits associated with caffeine could also come from the antioxidants in coffee and tea that destroy disease-causing free radicals in your body. Consequently, we need more research to better understand caffeine's long-term impacts.

How to use caffeine in a healthy way

Even though caffeine can produce unwanted side effects, healthcare providers still consider it safe. But Dr. Smith recommends only adding caffeine to your daily life in safe, healthy ways.

• Monitor your intake: Limit yourself to 400 mg of caffeine a day. That's about four cups of coffee. If you're pregnant, cap your daily intake at 200 mg.​ Kids under 18 should consume less than 100 mg of caffeine or avoid it altogether.

• Consume small amounts throughout the day: Sip coffee or tea throughout the day rather than consuming one large amount in the morning. This way, you'll have a steady, low-level energy bump over several hours.

• Cut yourself off: Stop drinking caffeine after a specific time, especially if you have trouble sleeping. Test out different quit times to determine which is best for your body.

• Choose healthy caffeine sources: Black coffee, tea (green, matcha or Earl Grey), yerba mate, kombucha and dark chocolate are healthy caffeine options.

• Avoid sugary caffeinated drinks: Sodas, lattes, energy drinks or other flavored coffee-based drinks contain more fat and lots of empty calories from sugar. These beverages can increase your risk of diabetes and lead to weight gain.

• Talk with your doctor: Caffeine impacts your heart and digestive system. If you have any chronic conditions, talk with your doctor about whether caffeine is safe.

Overall, Dr. Smith says, it's important to remember that caffeine has both positive and negative effects. Paying attention to how it impacts you is the best way to protect your health. Figuring out the right amount of caffeine for you can help you experience an enjoyable caffeine buzz. Just keep in mind that caffeine isn't a substitute for sleep.

“Caffeine can give you a great boost, but it's not free energy," he says. “That cup of coffee or tea won't eliminate your fatigue—it just pushes it off to another time. Eventually, you're still going to need the proper amount of sleep and rest."

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Looking for a primary care provider to help you feel your best? Call The Christ Hospital Physicians - Primary Care at 513-585-3000 to find a doctor near you!