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What Are the Negative Effects of Caffeine?

A cup of coffee contains about 100 mg of caffeine. Having 300 mg or more of caffeine a day can lead to negative effects.
Excess caffeine may cause heart palpitations.
Caffeine may cause stomach discomfort.
For some, caffeine can be part of a cycle of exhaustion and caffeine boosts.
Drinking a cup of coffee every day may lead to physical dependence on caffeine.
Caffeine may make it difficult to fall asleep.
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  • Written By: Tricia Ellis-Christensen
  • Edited By: O. Wallace
  • Last Modified Date: 04 December 2014
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The negative effects of caffeine are well documented, but not all research agrees on the results of caffeine. Some is specifically caffeine negative, citing numerous bad effects. Other studies take a more positive approach and cite both benefits and possible problems with caffeine consumption. Most studies correlate the negative effects with high caffeine intake, and with certain physical conditions or groups of people who tend to have more problems with caffeine.

A small amount of caffeine intake by a completely healthy person may have minimal effect. Caffeine is a stimulant and it will elevate heart rate, increase blood flow, and raise body temperature. It increases blood sugar levels and act as a diuretic, meaning you urinate more frequently and reduce water intake. Caffeine makes most users more alert, and some studies have suggested that it may reduce the risk of diseases like Parkinson's. People with certain conditions, or who consume large amounts of caffeine, may suffer more negative effects, however.

One of the negative effects of caffeine is that small amounts taken daily can create a physical dependence. If a regular coffee drinker, for example, fails to drink his daily dose of caffeine, he can end up with headaches, excessive sleepiness, a feeling like he cannot function. Withdrawal from caffeine can take anywhere from a few days to a few weeks depending upon how much caffeine a person customarily consumes.

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When caffeine intake is above 300 milligrams a day, about three cups of coffee or three to four sodas, the caffeine may at first make a person feel energized. Yet one of the negative effects of caffeine is its ability to disrupt sleep cycles, causing less deep sleep, particularly when the person drinks caffeinated beverages within a few hours of bedtime. So while a person may be using coffee or other caffeine laced beverages to "get started" in the morning, one reason he might need this extra boost because he is getting inadequate sleep.

In 2006, studies on night shift workers found that those who consume caffeine at night are most prone to this effect. Since night shift work already disrupts normal sleeping patterns, caffeine intake may create more serious issues. Those who drink caffeinated beverages and work the night shift have a far greater likelihood of getting insufficient deep sleep during the day. This can result in a continued cycle of exhaustion and caffeine boosts, a greater dependence on caffeine, and more caffeine consumed, which only exacerbates the problem.

Certain people are also particularly caffeine sensitive and more likely to experience negative effects of caffeine. For example, some people will feel "buzzed" or hyped up from one cup of coffee. Lower body weight tends to translate to higher likelihood of experiencing the negative side effects.

People with panic disorder or generalized anxiety disorder are much more prone to reacting badly from increased heart rate. Caffeine, even in small doses, can create panic attacks and interfere with medications taken to calm the system. Caffeine is a adenosine-receptor antagonist, meaning that it blocks the receptors in the brain that bind with the neuromodulator adenosine, which slows neural activity. It also promotes the release of adrenaline and dopamine.

For people with high blood pressure or high blood sugar levels, the negative effects of caffeine should be understood. Caffeine can raise both these levels. Any type of heart problem can be affected by caffeine. The negative effect of caffeine in increasing heart rate can create problems for people with heart conditions, and in high doses, caffeine can induce irregular heartbeats in healthy people.

People with stomach conditions like irritable bowel syndrome, Crohn's disease, ulcers, and gastro-intestinal reflux, may all suffer from consuming caffeine. Caffeine increases acidic response in the stomach which may lead to excessive bowel movements and is associated with stomach discomfort.

Negative effects of caffeine can be broken down into moderate and serious side effects:

Moderate effects include:

Severe effects include:

Though there are some positive effects of caffeine, the negative should be understood. Anyone in a high-risk group should be aware of the severe negative effects. People with mood disorders, high blood pressure, diabetes, heart disease, kidney disease, chronic intestinal issues, work the night shift or who are pregnant should minimize caffeine intake.

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Discuss this Article

anon927356
Post 38

I gave up caffeine and I don't remember having any headaches or anything else. Still, I don't eat or drink much caffeine at all. (Well, other than chocolate.)

anon321570
Post 37

I stopped drinking caffeine two years ago. I no longer feel tired in the morning after the first few minutes. I have so much more energy without this horrible stimulant.

I also don't need to pee as much.

anon315959
Post 35

It increases body temperature because it increases metabolic functions within the body. A product of these functions is heat.

anon293739
Post 33

I love caffeine, and have never had any associated negative health risks or side effects. Of course, I use in complete moderation so that could be why. Recently I've started using Energy Shots. A little different from coffee, but hey it works.

anon279883
Post 32

Does anyone know why stimulants increase body temperature? It says here they do, and I just need to know how for research I am doing.

anon278752
Post 31

I'm happy for all of you who have quit or are really trying to. Keep it up and stay strong! I've definitely learned some stuff about caffeine I didn't know. I don't drink copious amounts of coffee -- a cup a day at most, or maybe two. A bit strong I guess, but not really strong.

I do get headaches sometimes, and feel kind of depressed at times, and I usually look forward to drinking coffee. I knew it was possible to be addicted to caffeine, but I didn't know it could be making me depressed and giving me headaches. I went through and read all of the posts under the article. They have opened up my eyes.

anon232837
Post 28

My mom's British so we are big tea drinkers, but I unfortunately can't anymore due to anxiety issues.

anon188400
Post 26

No-one has mentioned caffeine and menopause. I get hot flushes, but these do decrease if I cut back on the coffee. I only have one cup per day, fairly weak, and weak black tea, (no milk). I am fructose free, having out out most products sweetened with whole sugar and artificial sweeteners. Anyone else having these results? Trying hard to give up. Will try the camomile tea. --Silver Angel

anon180398
Post 25

@number 21: First of all, do you think we have an unlimited supply of dopamine? no, it is produced at quite a steady rate and our reserves do not get higher than a certain point naturally.

So while it may increase the amount of dopamine being released it does not increase the amount being created resulting in a lack of dopamine. a good analogy would be going on a spending spree spending more money than you earn, then repeating it every day. constant caffeine abuse will leave you lacking dopamine and depressed.

anon174852
Post 23

I have given up coffee, along with all processed sugar. If you really want to sleep better amongst other benefits, engage in meditation. Find a teacher, meditate 20 minutes twice per day, and feel the calmness. Over a period of time, you will benefit physically, mentally, emotionally, and yes, even spiritually.

anon154273
Post 22

I've been drinking coffee off and on for over forty years and have realized how difficult it is to quit only over the last 15 or so years. When I first started drinking it I could quit for about five years at a time and not have it bother me. Then when I would have a cup I would be energized for hours. That's when I realized how strong it was and how much I liked it.

I also noticed, however, how irritable I get when having to deal with certain people, how talkative I become, and how rushed I am to get things done. By the end of the day I look wired and tired. It caused me to have rosacea, and the more I drink it, the more severe I get it.

When I became diabetic at about 48 years old I noticed over the years that it really increases my blood sugar levels a lot.

Even after realizing all these negative things it causes for me, I keep finding reasons to drink it. I get off of it for maybe a week, and though I feel great, I trick myself into having a cup. Hopefully some day I'll be able to let it go completely. --Russ

anon145446
Post 21

This article states something that is factually incorrect, which jeopardizes the credibility of the entire article and should be corrected.

It states, "Caffeine does reduce dopamine,...", when the opposite is true. Caffeine increases dopamine levels in the brain. Do your own research on the internet; the facts speak for themselves. I tried to offer web addresses for sources of this information, but it would not allow me to post these website addresses. There are many.

You will need to do your own research to verify. Just type "caffeine increases dopamine" into a search engine and you will get lots of articles.

anon135938
Post 19

For all you trying to kick the caffeine habit, try drinking Camomile Tea in place of coffee. You will be very surprised with the results.

anon131136
Post 18

To those who are smart enough to recognize a problem.

Three months ago, I successfully quit drinking coffee. It was wonderful. After a few days of withdrawal, I felt at peace. My nirvana lasted for a little more than two months.

However, I missed the smell, the taste, and the way the coffee made me want to call my friends and family and talk, talk, talk. So, I went back.

I tried one cup. I thought I was strong enough to enjoy one cup here and there and then continue to be free of caffeine. Curiosity killed the cat.

Now, I don’t drink as much as I used to, but, for some reason, I just can’t cope without going down to the local coffee shop and buying a cup.

For a few hours I feel great, but then, in the early afternoon, the anxiety kicks in, my stomach aches, my head hurts and I’m in a very bad mood. This is no good for my nine year old. I get very angry at him very easily. He was the reason I quit three months ago. I feel like this isn’t the person I am.

I am going to stop again. And the flu like symptoms? Spot on. Good luck to you soon to be ex-coffee drinkers. You are better people without coffee. I promise. Today is the day my friends. --Sincerely, Joseph

anon125269
Post 17

This is day five of me not drinking coffee. After reading some of these posts I realized that I wasn't much of an addict but I sure needed that cup or two of coffee, not to function properly, but to feel "happy" for some reason or another. I felt like coffee made me a nicer, more energized, happier person and when I didn't have it I felt irritable, annoyed, and angry.

I definitely feel like it took a toll on my body because I gained weight as I was drinking coffee for breakfast or lunch and even when I was being intimate, it would take so much longer (up to an hour) to feel anything! I also became severely sensitive to dairy and I was chugging at least a gallon of water daily because I was always thirsty.

A cup a day may be helpful but don't increase it and don't under any circumstance abuse it! School and work may be tough but you'll get through it if you try hard enough! I plan to stay coffee free for 25 more days and hopefully forever. I quit drinking soda two years ago and quit eating fast food a year and a half ago. I can do this!

anon122445
Post 16

I have just finished my first week of no caffeine (cold turkey) as i am on a 'candida diet'. I have had really bad restless leg syndrome (i haven't experienced that since being pregnant) for the second and third nights - it was like torture!

But it has subsided now and i am feeling great and sleeping like the dead! The smell of coffee is so appealing but i will be strong and know i am going to be loads healthier without caffeine!

anon100605
Post 14

I have been drinking from 100 to 180oz/day of Code Red Mt. Dew/regular dew for at least 20 years for the caffeine fix to prevent headaches. I tried to quit several times before i realized that the headaches (in my opinion) are not actually caused by the lack of caffeine, but are due to the lack of fluid intake.

When i would try to quit Mt. Dew, I noticed that I was not replacing it with other fluids. I gave up my Mt. Dew about three days ago and increased my water consumption. So far, no headaches and i have actually began dreaming again. It is great! Hope this helps someone in the future!

anon91959
Post 13

How to stop your coffee intake? I was addicted to coffee for 40 years and drank 12 or more cups per day.

Do it over a couple of months. Substitute one coffee every day for decaf and after a week substitute two of your coffees for decaf and so on. You will not have any of the withdrawal side effects if you do it this way. i am now completely off coffee and don't crave it at all.

Decaf is not something you will crave like coffee so i am now drinking milo, drinking chocolate, decaf and anything else that does not have a lot of caffeine in it. Cheers, Gail

anon84363
Post 12

these days children are more addicted to caffeinated drinks. The effects of these on kids, especially those below five years old need to be highlighted.

Secondly, should the manufacturers on these drinks be not made to indicate the quantity of caffeine present in each pack?

anon84223
Post 11

I love caffeine! It is like my life source! I can"t live without it. I can usually drink a whole pot in the morning before school and another pot after i get home from school. Am i addicted?

anon78907
Post 10

I gave up first coca-cola as it made me nauseous, then some years later I gave up coffee because by the end of the day I was feeling sick and had a headache.

Then maybe ten years later I noticed tea gave me a numb lip and a headache. I can tell if i am given normal tea as this happens almost immediately. I now only drink decaf.

anon76423
Post 9

I find that when I tried to didn't drink coffee I would get headaches, however, the times when I was trying to quit smoking and quit cigarettes and coffee at the same time, I did not get the headaches.

After trying to quit many times. A friend recommended a book called The Easy Way to Stop Smoking by Allen Carr. He told me something like 90 percent of the people who read the book quit smoking.

For some reason I wasn't skeptical at all and was actually excited. At the time I had been on the patch three days. Halfway through the book I ripped the patch off and then I continued to read the book. That was in January.

The first three weeks were the most difficult, but it was smooth sailing after that. I highly recommend the book. There is nothing to lose. Now I save $3,000 a year on cigarettes!

anon71342
Post 8

I've have been drinking coffee for at least 45 years, and i mean drinking coffee. i would sit down at my favorite coffee house before I started driving, and having three or four cups was normal. then something or someone and i would started talking about something hot, and well we just enjoyed ourselves, and drank even more. now it's normal for me to make a 12 cup pot and take with me on my run. I'm waking up on weekends like i now am reading with a headache, and have been for years. Thanks for the insight. now all i have to do is find out just how to stop.

anon70840
Post 7

I think this is why it says that it decreases Dopamine levels in the brain:

Caffeine will affect the neurons in such a way that dopamine acts longer in the synapse and causes a bigger response on the postsynaptic neuron (not sure if it's because caffeine blocks reuptake of dopamine or blocks its degradation). So in the short run the effect of dopamine is greater.

However, after a while your brain will start to notice that there is just too much dopamine stimulation on the postsynaptic neurons.

To protect itself from this overstimulation it will decrease the amount of dopamine receptors on these postsynaptic neurons (receptors is where dopamine binds to cause its effect on the postsynaptic neuron), giving dopamine less receptors to "work their effect on". Therefore, the effect of the dopamine release becomes less.

Since dopamine has been termed the "pleasure molecule" in the brain, its lessened effect due to long-term use of caffeine might make you feel more depressed.

So my guess is that caffeine increases DA in short run, and decreases it in long term.

anon67555
Post 6

I'm pretty sure caffeine increases dopamine in the brain. please correct me if i am wrong but several other internet sources seem to say the same thing. is there something i don't know about?

anon66914
Post 5

I totally had the same issue.. I would get a headache/migraine on the weekend and nothing through weekdays. -NA

anon63283
Post 4

I've been drinking coffee for about two decades. I've battled with insomnia and depression when a doctor suggested that I stop drinking coffee that it may be causing these effects. I couldn't imagine it then. Now I know I must let it go.

I experience great mood swings even fogginess in my thinking and a total blackout occurred. I hope I don't get extreme withdrawal. I have to overcome this. It's disturbing my mindset. I smoke cigarettes and drink coffee excessively. I'm trying decaf but I feel a difference. I will fight this battle.

anon12497
Post 2

Why is it that caffeine is actually a mental stimulant?

jennifers
Post 1

Another problem that is becoming more and more common is that people tend to drink coffee or other caffeinated beverages regularly on weekdays but on weekends they either sleep in or skip the coffee for other reasons and their body goes through withdrawal every weekend. This can manifest in migraines, anxiety, sleep problems, and many other ways.

I know one person who couldn't figure out why he was having an anxiety attack every weekend - it turns out that he just wasn't drinking three cups of coffee on Saturdays and Sundays like he did Monday through Friday.

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