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  • Caffeine 101: Tea, Coffee, and the Human Body
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Caffeine 101: Tea, Coffee, and the Human Body

Caffeine 101: Tea, Coffee, and the Human Body

Caffeine is the most unregulated stimulant in the world. The United States is one of caffeine’s heaviest users: 83% of adults in the United States drink coffee, and the average amount of coffee consumed by those drinkers is 3-4 cups a day. Without even taking into account the amount of soda the average American drinks, it’s obvious we’ve developed quite the reliance on caffeine in our day to day lives.

Not many of us are used to thinking of caffeine as a drug, but that’s what it is. Perfectly safe in moderation, but excessive consumption risks caffeine overload. While the side effects of too much caffeine probably won’t send you to the hospital, it can have some serious impact on your physical and mental health that shouldn’t be so easily dismissed.

You may be looking for a way to cut back on your caffeine intake, or for a way to better manage the side effects of too much caffeine. You might have even tried to cut back in the past unsuccessfully. You may be weary of going cold turkey and facing the possibility of caffeine withdrawl.  If you happen to be one of these average coffee drinkers, you are very much in luck. There is a way to get the caffeine you need to function without any of the negative side effects that might be bothering you: tea.

whole leaf teas release caffeine more slowly than ground coffee beans

You may have rolled your eyes at this advice before. How could a cup of tea possibly satisfy someone so used to drinking coffee for their energy boost? Read on. And maybe put off that 3rd or 4th cup of coffee until after you’ve read this, just to be safe.

Effects of Caffeine

Caffeine behaves in a unique way that affects you both physically and mentally.

Caffeine primarily functions by blocking the receptors that produce drowsiness. The chemical structure classifies it as being a xanthine (pronounced “zan-theen”). In addition, caffeine also causes energy to spike in the body, so it is also classified as a stimulant.

The modulator that produces the feeling of drowsiness (called adenosine) resides in the brain. But it also exists in other parts of the body, including the heart, lungs, liver, kidneys, and even in fat cells. This means that caffeine affects your entire body, perhaps in ways you haven’t realized. Have you ever noticed that the more coffee you drink the more you tend to breathe, or that your heart is pumping much faster than it normally is?

System by system, here is what caffeine does in the body:

  • The Heart: A single cup of coffee in the morning might not result in a faster heartbeat for everyone. But for people with high sensitivity, the heart is beating a full 10-20 beats faster per minute after 4 cups of coffee. That may sound like a lot, but keep in mind that the national average is 3 cups per day. High levels of caffeine can result in an irregular heartbeat and elevated blood pressure. For this reason, people with high blood pressure are usually told to avoid high amounts of caffeine.
  • The Kidneys: Caffeine blocks the adenosine receptors in your kidneys that are in charge of regulating waste, meaning you might find yourself visiting the bathroom far more frequently when you drink coffee rather than water.
  • The Digestive System: Along with the caffeine found in coffee, the acids and oils can work together to irritate the stomach lining and cause uncomfortable bloating. Even decaffeinated coffee has been known to irritate the stomach. For some, the combination of the caffeine and the acids it produces in the stomach can damage the protective lining of the stomach.
  • The Lungs: Xanthines, like caffeine, stimulate the rate of breathing, and some are actually prescribed as asthma medication. For coffee drinkers that are prone to panic attacks (or stress, as covered below) this can possibility contribute to the intensity of the attacks.

At a limit of just one cup of coffee per day, you’re not likely to experience these effects unless you happen to be sensitive to caffeine. But If you’re a heavy user, you’ve likely experienced all of these side effects at one time or another. And if you do consume high amounts of caffeine on a daily basis, I can guarantee you’ve struggled with perhaps the most serious side-effect of them all: Stress.

Caffeine and Stress

Caffeine directly affects your stress level.

Caffeine directly raises your blood pressure, and can contribute towards your stress level as well. From the PhD team that wrote Buzzed: The Straight Facts About the Most Used and Abused Drugs:

“ seems that caffeine users who find themselves under stress (or who use caffeine even more during stressful periods to work more effectively) may experience more of the effects that stress can produce.  Adrenaline release increases blood pressure during stress, and the caffeine-induced rise adds to this.  Thus, caffeine and stress together lead to greater bodily stress responses than either does alone.”

Caffeine has also been linked to an increase of panic attacks in those who already experience them. Very high doses can even increase the chances of panic attacks in people who have never experienced them. This means that relying on coffee or other high-caffeine beverages to manage your stress is actually only creating more stress!

But before you swear off all caffeine forever, let’s establish how much caffeine it really takes for these side effects to become a problem. Just like any drug, caffeine can be benign or even beneficial in moderation. It is our tendency to take in too much that results in negative side effects. For most people, avoiding those side effects can be a simple matter of consuming less caffeine.

If you happen to be asking, “But I’m used to the amount of caffeine I get now. How can I function on less?”

And the answer is: pretty easily. Because while I’m betting a lot of coffee drinkers might know some of these side effects of caffeine that I mentioned, I’m willing to bet that not many people realize how long caffeine lasts in the system.

How Long Does Caffeine Last?

Your body processes all the caffeine you consume, and it probably takes much longer than you think.

Your body absorbs caffeine quickly, but processes it very slowly. One study measured the half life of caffeine in the human body to be about 5.7 hours. This means that half of the caffeine from your first cup is likely still in your system nearly six hours later. Even after you’ve had your 2nd or 3rd cup for that midday slump, you’re still processing the morning’s brew. If you do consume more than one cup of coffee, you are amassing a store of caffeine that your body is still processing by the end of the day.  This is one reason why lots of caffeine can be detrimental to your sleeping patterns.

milligrams of caffeine in beverages

Take a look at the chart above.  These days, the average calorie content of your beverage is displayed on the menu board, but did you realize how much caffeine those drinks contain? Each extra shot in your latte is another 90 milligrams, more than double the amount in a cup of whole leaf tea.

Once you know the caffeine you take in builds up faster than your body can process it, does standing in line for coffee three times a day seem worth the effort? Now that you know you don’t actually need as much caffeine as you think you might, is there a better option to get the caffeine you need without the side effects?

Yes, there absolutely is.

Caffeine in Tea

Tea contains caffeine, as well as other compounds that can help relax and focus the mind

By drinking tea instead of coffee or energy drinks, you get all the caffeine you need, plus a natural way to relieve stress.

In fact, a dry tea leaf contains more caffeine than a coffee bean, but brewed tea is usually much more dilute than coffee. A whole leaf also offers less surface area than ground beans, slowing the extraction process. The result is a less caffeinated cup, but tea also has two very unique qualities that coffee does not have. Tea leaves contain built-in relaxants and antioxidants that work in harmony with caffeine to give you energy, as well as provide relaxing effects that benefit health.

While tea has been celebrated throughout Chinese history for its health properties, it’s health benefits have recently been recognized and marketed in the West, as well. Today, there are a range of health claims from a wide variety of sources, and it can be difficult to know what is actually true.

For that reason, all of the scientific studies cited here will be listed at the bottom of the page should you like to investigate for yourself after you finish reading. There’s lots of other fascinating aspects to tea and health we’re going to be discussing in the future, but today we’re going to be focusing on the two most studied compounds that cause relaxation: EGCG and L-Theanine.


EGCG is a natural antioxidant present in tea

Let’s start with EGCG, a powerful relaxant and antioxidant found naturally in tea leaves.  Antioxidants are polyphenols, which means they are chemicals naturally produced in plants that benefit human health. There are many types and they’re found in myriad vegetables and fruits. If you can list any of the popular “superfoods” marketed in the past few years, then you’ve heard about antioxidants.

In a nutshell, antioxidants combat cell damage caused by oxidants, which you can absorb through your environment, or through smoking and alcohol. Oxidants are also produced naturally in your own body. They can cause serious harm in high quantities. Antioxidants help to balance your system and promote cellular health.

Tea has a number of antioxidants, but EGCG has been studied very thoroughly and the results are quite promising for those who crave relaxation.

First, EGCG relieves both physical and mental stress. Research indicates that taking EGCG actually can improve your stress responses over time, meaning the effects apply to your health even when EGCG isn’t in your system.

It has also been linked to improving cognitive function and memory, especially in lifelong tea drinkers. This study examined the stress responses and memory of Chinese tea drinkers in China who had consumed tea for decades, and found significantly higher scores in memory and stress management than the group without tea drinking habits.

The best thing about EGCG is that while it relaxes you and soothes stress, it does so without causing drowsiness or limiting your attention capacity.


Tea is one of only a few plants that naturally contain L-Theanine

Similar to EGCG is L-Theanine, an amino acid that also soothes stress and induces relaxation in the brain by increasing the production of serotonin and dopamine. These neurotransmitters cause feelings of happiness and well-being. Like EGCG, L-Theanine does this without inducing drowsiness, and even seems to coordinate with the caffeine present in tea to produce a particularly potent form of mental energy.

L-Theanine is especially interesting to study, as it seems to naturally counteract every negative side effect too much caffeine can cause.  Lack of sleep? L-Theanine has not only been linked to better sleep as a natural sleeping aid, but also has no addictive tendencies (unlike many artificial sleep aids). Stress? L-Theanine decreases stress levels and even helps anxious people perform in stressful situations. High blood pressure? L-Theanine prevents the increase of blood pressure levels through it’s amazing stress-lowering capacity, and can even lower the blood pressure of the most stress-prone individuals. L-Theanine is even prescribed in heavier doses in some cases to help asthmatics manage their breathing.

This is why the natural state of tea is truly incredible. Tea combines two powerful and seemingly opposite elements together in a way that elevates both without detriment to the other: the stimulating effects of caffeine along with the soothing relaxants of EGCG and L-Theanine. Drinking tea allows you to harness the energy of caffeine without the intense stressful side effects of too much coffee, and provides all the mental energy you require.

So if you are someone who relies on caffeine to get through your morning, as you reach for your 2nd (or even your 3rd) cup of coffee, try to remember that you already might have all the caffeine you can handle. Instead, imagine brewing yourself a nice mug of tea. Chances are this will take less time than waiting on a new pot of coffee to percolate, and it will definitely take less time than standing in line to order a latte at a cafe.

The caffeine-tolerant out there can drink tea in bulk for the energy it brings, without the risk of a crash.The caffeine sensitive can easily manage their caffeine at a much more controlled rate. Best of all, anyone can enjoy the relaxing benefits of tea: less stress, better sleep, and sharper focus.


Buzzed: The Straight Facts About the Most Used and Abused Drugs from Alcohol to Ecstasy, 2008.

Statland BE, Demas TJ. Serum caffeine half-lives. Healthy subjects vs. patients having alcoholic hepatic disease. Am J Clin Pathol. 1980;73(3):390-3.

Gomez-pinilla F, Nguyen TT. Natural mood foods: the actions of polyphenols against psychiatric and cognitive disorders. Nutr Neurosci. 2012;15(3):127-33.

Adachi N, Tomonaga S, Tachibana T, Denbow DM, Furuse M. (-)-Epigallocatechin gallate attenuates acute stress responses through GABAergic system in the brain. Eur J Pharmacol. 2006;531(1-3):171-5.

Kuriyama S, Hozawa A, Ohmori K, et al. Green tea consumption and cognitive function: a cross-sectional study from the Tsurugaya Project 1. Am J Clin Nutr. 2006;83(2):355-61.

Unno K, Tanida N, Ishii N, et al. Anti-stress effect of theanine on students during pharmacy practice: positive correlation among salivary α-amylase activity, trait anxiety and subjective stress. Pharmacol Biochem Behav. 2013;111:128-35.

Camfield DA, Stough C, Farrimond J, Scholey AB. Acute effects of tea constituents L-theanine, caffeine, and epigallocatechin gallate on cognitive function and mood: a systematic review and meta-analysis. Nutr Rev. 2014;72(8):507-22.

Alramadhan E, Hanna MS, Hanna MS, Goldstein TA, Avila SM, Weeks BS. Dietary and botanical anxiolytics. Med Sci Monit. 2012;18(4):RA40-8.

Dulloo, A G et al. "Green Tea And Thermogenesis: Interactions Between Catechin-Polyphenols, Caffeine And Sympathetic Activity". N.p., 2000. Print.

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Higashiyama, Akiko et al. "Effects Of L-Theanine On Attention And Reaction Time Response". N.p., 2011. Web. 31 May 2017.

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Comments on this post (1)

  • Jun 01, 2020

    Free Caffeine 101: Tea, Coffee and the Human Body Course.
    What valuable information. Thank you Alice for providing this. I only have a small decaf latte 3 or 4 times a year because even though I enjoy the taste, I have to have a lot of milk with the one shot of coffee so that it doesn’t upset my stomach. Milk doesn’t upset me. I have never enjoyed a dinner time coffee with cream so I would pass on it while others would have two cups! With your permission I would like to forward your article on to a couple of my friends here in Canada. If you would rather I didn’t, it’s OK, I won’t do it.

    I am a senior and have been drinking black tea all my life. I don’t like it strong, a three minute brew is good for me and it has to be really hot. because I take it with milk.. I don’t take sugar because I am diabetic.

    I have known for years that there are very many different types of green tea and that they are all very beneficial but even though I have tried it many times, I cannot stand the taste of it. It actually makes me retch! I was looking on the internet for ways to improve the taste so I could try it again when I found your website. After watching three of your videos I NOW realize the whole subject is far more complex than I ever imagined. I had no idea the process is similar to the wine industry. Goodness only knows what brands of green tea I was trying to drink and yes, they were tea bags!!!

    Thank you for giving this free Caffeine 101: Tea, Coffee and the Human Body Course. I am in awe of your knowledge of the whole extensive process of providing high quality teas teapots and mugs. I look forward to learning more from you.

    Be safe in this stressful time of COVID 19.. Kind regards, Barbara

    — Barbara Till

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