90% of adults around the world use caffeine on a daily basis [1, 2]. Up to a point, caffeine is not a bad thing. In fact, moderate caffeine intake has been shown to enhance cognition and performance and reduce the risk of certain health conditions like liver disease, Parkinson’s, Type 2 Diabetes, and more [3, 4]. That said, there is also such a thing as too much.
How Caffeine Works
Caffeine works by stimulating the central nervous system via adenosine receptors . This results in an increase of stimulatory neurotransmitters like adrenaline, glutamate, dopamine, and cortisol along with an accompanying increase in blood pressure and heart rate.
Caffeine and Stress
What does all of that mean? The answer: It depends on stress. The mechanism by which caffeine stimulates the nervous system helps the average person feel focused and concentrated and can even improve workout performance. But for the stressed individual, it’s a different story .
When stressed, loading up on caffeine may not yield the same positive results for focus and performance. In fact, research shows it may backfire. In a randomized control trial, individuals under stress who consumed caffeine had increased cortisol and adrenaline production, elevated blood pressure, and an increase in perceived stress [7, 8]. Bottom line. Caffeine may exacerbate a stressed-out body and mind!
The Devil is in the Dose
Not only is the impact of caffeine impacted by stress, but it is also impacted by the dose - or how much coffee you are consuming. We are all familiar with that racing heart, sweaty palms feeling that hits when you’ve had too much coffee on an empty stomach or been pounding caffeinated tea all day.
In the U.S., adults consume an average of 135 mg of caffeine daily. This is typically the amount in 1.5 cups, or 12 ounces, of coffee9. The FDA’s recommended daily limit for caffeine intake is 400mg/day for healthy adults, which is equivalent to 4-5 cups of coffee10. Keep in mind this upper limit may be far too much if you are stressed.
In general, we should all limit caffeine intake - especially after noon - but that is especially true if you are experiencing stress. A good rule of thumb is to limit caffeinated drinks to 1-2 per day, though knowing how your body responds to stress by testing your cortisol can help you better identify your unique tolerance level.
The Bottom Line
Caffeine can increase your stress response and worsen symptoms of anxiety, nervousness, headaches and poor sleep. Your ability to metabolize caffeine is unique and finding a moderate dose of caffeine that you tolerate is a great goal.
Remember that abrupt withdrawal of caffeine can cause withdrawal symptoms, so reduce your dose slowly, and keep track of how you feel as you go. Your caffeine sweet spot will be unique to you, and it may change as your stress levels do.
- Celine Marie Reyes and Marilyn C. Cornelis. Caffeine in the Diet: Country-Level Consumption and Guidelines. Nutrients. 2018 Nov; 10(11): 1772. doi: 10.3390/nu10111772
- Diane Mitchell, Carol Knight, et al. Beverage caffeine intakes in the U.S. Food and Chemical Toxicology. Volume 63, January 2014, Pages 136-142. https://doi.org/10.1016/j.fct.2013.10.042
- M J Jarvis. Does caffeine intake enhance absolute levels of cognitive performance Psychopharmacology (Berl). 1993;110(1-2):45-52. doi: 10.1007/BF02246949
- Donald Hensrud, M.D. Does Coffee Offer Other Benefits. Mayo Clinic. Healthy Lifestyle. Nutrition and Healthy Eating.
- Brian Fiani, Lawrence Zhu, Brian L Musch, et al. The Neurophysiology of Caffeine as a Central Nervous System Stimulant and the Resultant Effects on Cognitive Function. Cureus. 2021 May; 13(5): e15032. doi: 10.7759/cureus.15032
- Santosh Kumar, Prajapati Durgesh, Singh Dangi Sairam Krishnamurthy. Repeated caffeine administration aggravates post-traumatic stress disorder-like symptoms in rats. Physiology & Behavior Volume 211, 1 November 2019, 112666. https://doi.org/10.1016/j.physbeh.2019.112666
- The Effect of Coffee and Caffeine on Mood, Sleep, and Health-Related Quality of Life. March 2017 • Journal of Caffeine Research DOI:10.1089/jcr.2016.0023
- Land JD, Adcock RA, Williams RB, Kuhn CM. Caffeine effects on cardiovascular and neuroendocrine responses to acute psychosocial stress and their relationship to level of habitual caffeine consumption. Psychosom Med. 1990 May-Jun;52(3):320-36. • DOI: 10.1097/00006842-199005000-00006
- Drewnowski A, Rehm CD. Sources of caffeine in diets of US children and adults: trends by beverage type and purchase location. Nutrients. 2016 Mar;8(3):154
- Food and Drug Administration. How Much Caffeine is Too Much Caffeine? December 2018