search
Health Insiders
Caffeine – The Unbiased Scientific Truth, Evidence-Based Health Benefits, How to Take, & Side Effects

Caffeine – The Unbiased Scientific Truth, Evidence-Based Health Benefits, How to Take, & Side Effects

Learn more about Caffeine's possible side effects, dosage, potential benefits including research and other important information here!

caffeine

Caffeine is a psychoactive substance that occurs naturally in coffee. (Photo by Burst from Pexels)

 

What is Caffeine?

Did you know that caffeine is considered a psychoactive drug?[1]

Caffeine is a powerful stimulant found naturally in plants such as coffee beans, tea leaves, and cocoa beans.

Humans around the world have been drinking coffee and tea for thousands of years. Currently, coffee is the most frequently consumed beverage all over the world (asides from water). The average American consumes about 2 cups of coffee a day[1].

It can also be found in other forms, like in energy drinks, soft drinks, and supplements.

 

How Does Caffeine Work to Affect Wakefulness?

It is common knowledge that caffeine can give us a boost of energy when we are feeling fatigued or didn’t have a good night’s sleep. But what exactly is caffeine doing in our bodies?

Caffeine suppresses adenosine from acting in the brain. Adenosine is a neurotransmitter responsible for sleepiness and relaxation.

Throughout the day, your levels of adenosine rise. Adenosine and caffeine molecules look very similar. When you ingest caffeine, it competes with adenosine for adenosine receptors.

Once caffeine binds to these receptors, it won’t activate the adenosine receptors since caffeine isn’t identical to adenosine. But this action prevents adenosine from activating the receptors.

So instead of feeling tired as the day progresses, it can increase alertness and combat fatigue.

In addition, neurons begin to fire rapidly which directs the pituitary gland to release hormones. This hormonal release signals the adrenal glands to produce adrenaline.

Adrenaline has several effects on the body which are meant to protect us when in danger. This response is commonly known as our “fight, flight, or freeze” response.

Part of this bodily response includes blood vessel constriction, decreased ability to feel pain, an increase in strength, and heightened awareness. Evolutionary speaking, these responses used to come in handy when our lives were at risk.

However, when you are sipping a latte in a local cafe on your coffee break, you aren’t generally under physical attack. Therefore, you may experience other effects such as light-headedness, restlessness, nervousness, insomnia, and, over time, even heart damage.

Caffeine also increases dopamine which is the “feel-good” neurotransmitter[2]. Dopamine is key to managing several mood disorders such as depression. Caffeine dependence may be related to this increase of dopamine.

 

What Are The Evidence-Based Health Benefits of Caffeine?

Caffeine consumption has been associated with a lower risk of developing:

  • Dementia[3]
  • Alzheimer’s disease[3]
  • Parkinson’s disease[4]
  • Cirrhosis of the liver[5]
  • Liver cancer[6]
  • Colon cancer[7]
  • Erectile dysfunction[8]

 

Can Caffeine Support Weight Loss?

Some evidence shows it can act as a thermogenic (increases heat production) which could aid weight loss. In addition, when taken before exercise, caffeine may help release stored fat[9].

However, relying on caffeine alone to achieve your weight loss goals is not advisable.

There are much safer and more sustainable ways to lose weight. This can look like eating a whole food plant-based diet, regular physical activity, stress management and reduction, and quality sleep.

 

Does Caffeine Improve Cognitive Performance?

Caffeine may enhance long-term memory. One study that was conducted by researchers at Johns Hopkins University found that caffeine could enhance memory for 24 hours after consumption. The reasons for this improvement in memory are still to be determined[10].

 

Can Caffeine Improve Physical Performance?

Caffeine is commonly added to energy drinks and pre-workout supplements. The reason for this is caffeine may provide increased anaerobic and aerobic capacity possibly due to its ability to combat fatigue.

Endurance athletes, such as cyclists, may perform better when using high doses of caffeine than even carbohydrates or water[11]. Although, the combination of carbohydrates and caffeine may have an even greater effect[12].

Other research supports its use in weightlifting as caffeine appears to increase power output.

However, the impact on athletic performance may change based on your level of athletics. It seems that the beneficial effects of caffeine generally only occur in highly trained individuals but not as much in untrained individuals[13].

 

How Does Caffeine Affect Stress?

In times of high stress, like with a work deadline approaching, you may be tempted to chug a cup of coffee to complete the task. However, caffeine consumption triggers the release of cortisol and adrenocorticotropin (which regulates cortisol).

Cortisol, also known as the stress hormone, is responsible for maintaining energy balance throughout the day. Increased levels of cortisol have been associated with a host of health issues including unintentional weight gain, diabetes, and heart disease.

So, perhaps an alternative with less caffeine, like tea, maybe smarter during times of high stress for your long-term health.

 

Will Caffeine Affect My Sleep?

Since caffeine increases wakefulness, it makes sense that it would have an impact on your ability to fall asleep. You should keep in mind that the half-life of caffeine is about 5-6 hours. This means it will take 5-6 hours to eliminate just half of the caffeine you ingested.

Other considerations to account for which will affect caffeine’s half-life include your age, body weight, what medications you’re using, whether you are pregnant, and the health of your detoxification organs.

Therefore, a late afternoon cup of coffee may affect you still when it is time to go to sleep.

Caffeine may also negatively impact your quality of sleep.

It is advisable to avoid caffeine in the afternoon or evening in order to get a full night’s rest.

 

How Much Caffeine Should You Take?

An 8-ounce cup of coffee contains about 80-100 mg of caffeine while a cup of black, white, or green tea contains between 14-61 mg (FDA)[14]. However, the amount of caffeine can vary depending on the type of coffee, how it is brewed, and how long it is brewed.

Your individual dose is also going to be based on your body weight and what the intended purpose is. For most people, a typical dose is between 200-400 mg.

Supplements are available as well which are generally at higher doses. However, you may miss out on the antioxidants in a cup of coffee if taking the isolated caffeine anhydrous instead.

Energy drinks are popular, especially among youth. They contain very high doses of both caffeine and sugar. Therefore, energy drinks have been associated with harmful side-effects, including cardiovascular risks[15].

 

Possible Side Effects and What to Be Aware Of

Over time, you will become tolerant to the effects of caffeine. The benefits of caffeine also become reduced. Therefore, people often find they need to increase caffeine intake to have the same desired effect as previously. This can lead to caffeine dependence.

You may even experience withdrawal symptoms like headaches, irritability, and sleepiness when you don’t consume caffeine.

Since caffeine is a stimulant, consumption may be dangerous for those with high blood pressure or other cardiovascular health concerns.

Caffeine causes vasoconstriction, which is where your blood vessels narrow, and blood flow is restricted. It can also increase heart rate, particularly in high doses and for those with low tolerance.

For people with diabetes or pre-diabetes, the effect of caffeine is unclear. Caffeine doesn’t appear to affect fasting insulin levels (either positively or negatively), however, blood sugar levels can rise after caffeine consumption[16].

In addition, it may decrease insulin sensitivity, particularly when ingested with carbohydrates.

Some medications can enhance the effect of caffeine. For example, the oral contraceptive pill can double the half-life of caffeine[1][17]. This means that the morning cup of joy may hit you harder and longer if you are on the birth control pill.

During pregnancy, the half-life of caffeine is also extended. The caffeine can transfer to the fetus potentially affecting development which is why caffeine during pregnancy is cautioned. The exact amount advised during pregnancy is a good conversation to have with your medical provider.

Likewise, children should avoid caffeine as the effects on development are still unknown.

Some people notice increased anxiety after ingesting caffeine. Therefore, caffeine may not be a good idea if you have experienced panic attacks or anxiety disorders.

Research shows that genetic variants may be responsible for the link between anxiety prompted by caffeine consumption and experiencing panic attacks[18]. This would explain why some people don’t experience increased anxiety with caffeine, while others witness a notable effect.

 

Conclusion

Caffeine consumption, in low to moderate doses, seems to be safe for most individuals. It may even be beneficial in preventing long-term diseases related to cognitive decline, and even various cancers.

Before exercise may be the most beneficial time to reap extra benefits physically. However, the time of day matters.

You may want to experiment with the timing of your tea and coffee consumption. If you have trouble falling asleep, it can help to take note of how late you are consuming coffee, tea, or chocolate. Setting a cut-off time can be helpful in managing caffeine consumption and sleep.

There are cautions to be made for certain groups, as outlined previously. In addition, developing a dependency is common and should be avoided.

Feedback:

References

Health Insiders uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial policy to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

1. Temple JL, Bernard C, Lipshultz SE, Czachor JD, Westphal JA, Mestre MA. The Safety of Ingested Caffeine: A Comprehensive Review. Front Psychiatry. 2017;8:80. Published 2017 May 26. doi:10.3389/fpsyt.2017.00080
2. Volkow, N. D., et al. "Caffeine increases striatal dopamine D 2/D 3 receptor availability in the human brain." Translational psychiatry 5.4 (2015): e549-e549.
3. Eskelinen, Marjo H., and Miia Kivipelto. "Caffeine as a protective factor in dementia and Alzheimer's disease." Journal of Alzheimer's Disease 20.s1 (2010): S167-S174.
4. Ross, G. Webster, et al. "Association of coffee and caffeine intake with the risk of Parkinson disease." Jama 283.20 (2000): 2674-2679.
5. Corrao, Giovanni, et al. "Coffee, caffeine, and the risk of liver cirrhosis." Annals of epidemiology 11.7 (2001): 458-465.
6. Tamura, Takashi, Asahi Hishida, and Kenji Wakai. "Coffee consumption and liver cancer risk in Japan: a meta-analysis of six prospective cohort studies." Nagoya journal of medical science 81.1 (2019): 143.
7. Schmit, Stephanie L., et al. "Coffee consumption and the risk of colorectal cancer." Cancer Epidemiology and Prevention Biomarkers 25.4 (2016): 634-639.
8. Lopez, David S., et al. "Role of caffeine intake on erectile dysfunction in US men: results from NHANES 2001-2004." PloS one 10.4 (2015).
9. Spriet, L. L., et al. "Caffeine ingestion and muscle metabolism during prolonged exercise in humans." American Journal of Physiology-Endocrinology And Metabolism 262.6 (1992): E891-E898.
10. Borota, Daniel, et al. "Post-study caffeine administration enhances memory consolidation in humans." Nature neuroscience 17.2 (2014): 201.
11. Ivy, J. L., et al. "Influence of caffeine and carbohydrate feedings on endurance performance." Pulse 1620.16.18 (1979): 1693.
12. Hulston, Carl J., and Asker E. Jeukendrup. "Substrate metabolism and exercise performance with caffeine and carbohydrate intake." Medicine & Science in Sports & Exercise 40.12 (2008): 2096-2104.
13. Collomp, K., et al. "Benefits of caffeine ingestion on sprint performance in trained and untrained swimmers." European journal of applied physiology and occupational physiology 64.4 (1992): 377-380.
14. Chin JM, Merves ML, Goldberger BA, Sampson-Cone A, Cone EJ (October 2008). "Caffeine content of brewed teas". Journal of Analytical Toxicology. 32 (8): 702–4.
15. Chrysant, S. G., and G. S. Chrysant. "Cardiovascular complications from consumption of high energy drinks: recent evidence." Journal of human hypertension 29.2 (2015): 71-76.
16. Pasman, Wilrike J., and Petra Verhoef. "Effects of coffee consumption on fasting blood glucose and insulin concentrations." Diabetes care 27.12 (2004).
17. Abernethy DR, Todd EL. Impairment of caffeine clearance by chronic use of low-dose oestrogen-containing oral contraceptives. Eur J Clin Pharmacol (1985) 28:425–8. doi:10.1007/BF00544361
18. Banks, N.F., Tomko, P.M., Colquhoun, R.J. et al. Genetic Polymorphisms in ADORA2A and CYP1A2 Influence Caffeine’s Effect on Postprandial Glycaemia. Sci Rep 9, 10532 (2019). https://doi.org/10.1038/s41598-019-46931-0
Author
Facebook pinterest Twitter instagram instagram

Dr. Dylan Cutler, PhD

Dr. Dylan Cutler is a PCOS Wellness Consultant, holistic health content creator, fitness enthusiast, feminist, and vegan. She obtained ...

Advertisement

immune defenceimmune defence

More Posts

View All
X

How helpful was it?

icon This article changed my life! icon This article was informative. icon I have a medical question.
X

How helpful was it?

icon This article changed my life! Change
Your Rating
Note: Health Insiders isn't a healthcare provider. We can't respond to health questions or give you medical advice.
Your Privacy is important to us.
X

How helpful was it?

icon This article was informative. Change
Your Rating
Note: Health Insiders isn't a healthcare provider. We can't respond to health questions or give you medical advice.
Your Privacy is important to us.
X
icon I have a medical question. Change

We’re unable to offer personal health advice, but we’ve partnered with JustAnswer who offers on-demand doctors to answer your medical questions 24/7. Talk online now with a doctor and get fast 1-on-1 answers from the comfort of your couch.

just answer logo
ASK A DOCTOR NOW

If you’re facing a medical emergency, call your local emergency services immediately, or visit the nearest emergency room or urgent care center.

X

How can we improve it?

icon This article contains incorrect information. icon This article doesn’t have the information I’m looking for. icon I have a medical question.
X

How can we improve it?

icon This article contains incorrect information. Change
Your Rating
Note: Health Insiders isn't a healthcare provider. We can't respond to health questions or give you medical advice.
Your Privacy is important to us.
X

How can we improve it?

icon This article doesn’t have the information I’m looking for. Change
Your Rating
Note: Health Insiders isn't a healthcare provider. We can't respond to health questions or give you medical advice.
Your Privacy is important to us.
X
icon I have a medical question. Change

We’re unable to offer personal health advice, but we’ve partnered with JustAnswer who offers on-demand doctors to answer your medical questions 24/7. Talk online now with a doctor and get fast 1-on-1 answers from the comfort of your couch.

just answer logo
ASK A DOCTOR NOW

If you’re facing a medical emergency, call your local emergency services immediately, or visit the nearest emergency room or urgent care center.

X

Healthinsiders.com is intended to be used for educational and information purposes only. All Health Insiders content is medically reviewed and fact-checked by a board of medical experts to ensure accuracy.

In keeping with our strict quality guidelines, we only cite academic research institutions, medical authorities, or peer-reviewed studies in our content. You will be able to find links to these sources by clicking the numbers in parentheses (1, 2, etc.) that appear throughout our content.

Medical Disclaimer: This product/supplement review is not intended to provide diagnosis, treatment, or medical advice. Please consult with a physician or other healthcare professional regarding any medical or health-related diagnosis or treatment options.

Health Insiders does not assume liability for any actions undertaken after visiting these pages and does not assume liability if one misuses supplements. Healthinsiders.com and its Editors do not ensure that unforeseen side effects will not occur even at the proper dosages, and thereby does not assume liability for any side effects from supplements or practices hosted under the domain of Healthinsiders.com.

We invite you to contact us regarding any inaccuracies, information that is out of date, or any otherwise dubious content that you find on our sites via our feedback form.