By Jen Hatz MS, RD, CSSD, LDN, CSCS
Caffeine is easily one of the most popular substances in the world. With its popularity though, there’s also a wide array of information, as well as misinformation, that can seem confusing or even conflicting. Let’s break down some of the in’s and out’s of caffeine consumption to break up that confusion.
First, what exactly is caffeine?
Caffeine is a naturally-occurring compound found in up to 60 different plant species, most commonly in coffee, tea, kola, and cocoa to name a few. It acts as a central nervous system stimulant, where it’s shown to impact alertness, mood, reaction time, decision making, and can even affect muscle contraction and perceived effort during physical activity. (1, 2) Caffeine is therefore considered an ergogenic aid where the physical and cognitive effects can help prolong output of high powered or long duration activity. (1,2) There’s also growing research to show potential benefits of caffeine for cognitive health where, for instance, chronic caffeine intake was reportedly linked with a lower risk of neurodegenerative diseases like Alzheimer’s disease.(1, 3) It’s also utilized in many headache and migraine treatments, possibly due to it’s vasoconstrictive properties. (1, 4)
In addition to physical and cognitive effects, caffeine can also help mobilize fatty acids from storage, a process known as lipolysis, which may be noteworthy in efforts to access and manage body fat stores. (1) It’s important to note that caffeine is not “burning” or metabolizing, or oxidizing fatty acids but rather helping to liberate fatty acids from storage. (1) The only thing that can actually oxidize a fatty acid is oxygen, so if the conditions aren’t appropriate to sufficiently utilize oxygen, like during lower intensity cardio exercise for instance, then those fatty acids can go back into storage for future use.
Unsurprisingly caffeine is therefore found in a wide variety of supplements and commonly sought-after beverages ranging from sports performance supplements like pre-workout powders and drinks, to products marketed as weight-loss or “fat-burning” supplements, to the wide variety of energy drinks and endlessly available coffee shops on every corner. While the appeal for caffeine is strong, and the effects can serve a benefit, there are some important things to keep in mind.
Coffee is Not a Meal
Caffeine, despite enhancing our alertness, is not energy and does not provide energy. It does not provide calories or nutritional value. We might feel more awake from the stimulatory effect, but in reality energy for human beings is measured in calories, and the only source of calories that a human being can take in is in food. Food provides you with the energy and the nutritional content that you need to actually function, build, repair, and thrive. Substances like caffeine then can be utilized as a supplement to your overall diet to help you in areas specific to its effects. (So coffee alone is not a meal!)
When can it be helpful? Once nutrition, hydration, and sleep are dialed in and accounted for, the addition of caffeine can help provide effects at potentially crucial times for physical or mental effort or activity, like when high demands for concentration are paramount. If physical activity requires a high power output or long duration, the strategic use of caffeine can help to mitigate the effects of fatigue to help prolong work output.
When can it be harmful? Caffeine can be harmful if used inappropriately like in replacement of food calories, hydration, and sleep where the absence or inconsistency of these cannot be made up with the stimulatory effects of caffeine. Abnormalities with nutritional status and sleep will continue to worsen and potentially lead to drastic negative effects in work performance or even injury if they continue to go unaddressed. A dependence on caffeine could therefore be masking an underlying deficiency elsewhere across other lifestyle factors that may need to be addressed.
The dose really does matter!
Too little or too much will leave you feeling less than thrilled so there’s a dose range that has been shown to have the greatest positive effects. Caffeine intake between 100-400mg, or 3-5mg/kg body weight, has been shown to be an ideal range for achieving the physical and cognitive effects, or ergogenic benefits. (1) Caffeine can be harmful though if taken in too high of a dose, seen with increased heart rate, blood pressure, anxiety, agitation, GI disturbances, insomnia, and tremors, and can even be toxic at extremely high doses or if co-ingested with other substances like drugs, alcohol, or nicotine. (1)
What does a dose look like? Caffeine concentrations can range widely depending on the product or drink. As a general rule of thumb, one cup of coffee may have 100-120mg, one cup of tea may have 60-80mg, one standard energy drink may have between 80-300+mg, depending on the type and size. Beverages like coffee and tea may differ drastically in the actual caffeine concentration due to differences in the brewing method or conditions. For example, the caffeine content of a cup of drip coffee differs from a cold-brewed coffee and from a nitro cold-brewed coffee. Even the same coffee drink that is made in the same coffee shop can differ each day in the actual caffeine content from slight changes in daily brewing conditions. Other products that contain caffeine include sodas, with Mountain Dew containing about 55mg, and even over-the-counter medications like excedrin containing 200mg.
Supplements or manufactured products may appear to have more standardization of the caffeine dose by following procedures like listing the caffeine content on the label, but there’s an important distinction to keep in mind. Supplements that are not third-party tested do not need to meet any standards for labeling, safety, and efficacy, and beverages or products like energy drinks are not always considered supplements. This means a product on the shelf may not have any standards to abide by when it comes to disclosing what it contains, the actual doses, and that the product itself does what it claims it will do. Keep an eye out for products that don’t contain a third-party testing verification, and products that list a proprietary blend, as there’s a lot of unknown factors at play.
Not everyone experiences the same effects!
Due to differences in individual genetics, the rate of absorption, uptake, and metabolism can differ widely. Caffeine is metabolized in the liver and very quickly distributed throughout the body where peak plasma concentrations typically occur within 30-60 mins of ingestion, but can range between individuals as much as 15-120 minutes. (1) The half-life of caffeine, or the amount of time it takes for half of the circulating concentration to be metabolized or used or lowered, can actually range between 2-12 hours, but with 5-6 hours most common. (1) This means it might take on average 5-6 hours for half of the dose you ingested to be used and no longer circulating. So even though it was only one cup of coffee in the afternoon, half of that caffeine dose is still circulating by the evening!
These individual differences mean some individuals may be extremely sensitive or have a low tolerance, whereas others may have a much higher tolerance. (1) Some individuals may even seem to still fall asleep easily after ingesting caffeine, however the large majority of us may experience disrupted sleep patterns from caffeine’s lingering stimulatory effects. It’s suggested to refrain from caffeine at least 5-6 hours prior to bedtime at a minimum, and to monitor for overall caffeine intake. Insufficient sleep coupled with high caffeine intake could be perpetuating the cycle.
If tolerance increases to the point that more frequent or larger doses are regularly consumed, then temporary changes in daily consumption may be needed in order to lower your tolerance, or increase your sensitivity, so that you are not establishing a dependence or potentially risky co-ingestion of items. The good news is, this tolerance can reportedly be “reset” where some findings suggest that habitual caffeine users can increase their ability to uptake caffeine similar to non-habitual users after 4-8 weeks of abstinence. (1) You might want to slowly lower your intake over a few days instead of going cold-turkey, or have a few days of the week with purposefully lower caffeine doses compared to others to provide some variety in intake.
It’s important to track how much is being ingested at once, especially if coming from multiple sources. The greatest indicators for potential issues stem from individual differences in absorption and metabolism, pre-existing conditions, and interactions with other substances, whereas the majority of caffeine users exhibit mild to no undesirable side effects. (1)
Is there a benefit in one source of caffeine over the other?
Naturally derived caffeine in coffee and tea will largely be readily available anywhere in the world but may have varying amounts of caffeine, which is largely unknown at the time of consumption. Caffeine-containing products and drinks like energy drinks, pre-workout supplements, and other forms of manufactured products may be less readily available if traveling, and may likely contain other substances or ingredients that may or may not be useful, safe, or well-tolerated. Depending on the product and its testing or verification, there may be more standardization with what you are actually taking in and the dose, or the complete opposite with an unknown and undisclosed “proprietary blend” of ingredients and doses.
The big differences though may come down to ease of access, the transparency of what you are taking in, the standardization of the dose if available, and the reason for taking in caffeine or the purpose it is serving for you at the time. Knowing your own individual tolerance is key, as well as continually checking in with your needs.
When you’re about to reach for more caffeine, ask yourself these questions first:
Is your nutrition, hydration, and sleep all in solid standing? (When did you last eat; what’s your water intake for the day; what did sleep look like last night?)
What exactly is the goal or the situation you’re looking at, and what are the effects you’re hoping to get from the caffeine?
How much have you already had today and how long ago? (If you’re taking in more than usual, you may need to lower your intake for a bit to “reset” your tolerance)
How much time is left for the day before bedtime?
Is this a typical dose for you, higher, or lower than what you’re used to?
Have you had any other substances, or will you in the near-future? (If you’re heading out to happy hour in a bit, mixing caffeine with alcohol may not be the best decision.)
Stay on top of your daily habits and how you respond so you can decide what works best for you!
Cappelletti S, Piacentino D, Sani G, Aromatario M. Caffeine: cognitive and physical performance enhancer or psychoactive drug? [published correction appears in Curr Neuropharmacol. 2015;13(4):554. Daria, Piacentino [corrected to Piacentino, Daria]]. Curr Neuropharmacol. 2015;13(1):71-88. doi:10.2174/1570159X13666141210215655
Mielgo-Ayuso J, Marques-Jiménez D, Refoyo I, Del Coso J, León-Guereño P, Calleja-González J. Effect of Caffeine Supplementation on Sports Performance Based on Differences Between Sexes: A Systematic Review. Nutrients. 2019;11(10):2313. Published 2019 Sep 30. doi:10.3390/nu11102313
Londzin P, Zamora M, Kąkol B, Taborek A, Folwarczna J. Potential of Caffeine in Alzheimer’s Disease-A Review of Experimental Studies. Nutrients. 2021;13(2):537. Published 2021 Feb 6. doi:10.3390/nu13020537
Lipton RB, Diener HC, Robbins MS, Garas SY, Patel K. Caffeine in the management of patients with headache. J Headache Pain. 2017;18(1):107. Published 2017 Oct 24. doi:10.1186/s10194-017-0806-2