Do you have to avoid coffee and caffeine after a concussion (mild traumatic brain injury)?
Quick Summary: The research on caffeine in concussion/mTBI needs to be more extensive. That said, avoiding caffeine in the first minutes to hours after a concussion is best. After the acute period of 24-72hrs, however, so long as caffeine is consumed in "normal doses" (100-300mg/day) before 12pm ("noon"), it likely will not impact recovery for better or worse. It's important to note that caffeine withdrawal symptoms closely match some concussion symptoms (e.g., headache, drowsiness, and difficulty concentrating). On the flip side, caffeine can improve visual processing speed, reaction time, and memory, and we do not know if the effect is strong enough to create premature clearance decisions for return to sport.
Other common questions:
How long after a concussion can you drink alcohol?
Can you take Ibuprofen for a concussion?
How long should you stay awake after a mild traumatic brain injury/concussion?
Let's break this down a bit.
Caffeine is arguably the world's most popular drug, with roughly 87% of American adults consuming caffeine (mostly from coffee and tea). Interestingly, 36-56% of North American children consume caffeine. According to the data from the US military, caffeine is a stimulant that will cause beneficial cognitive and physical endurance effects in nearly everyone at doses between 100-600mg. While "caffeine addiction" is not an official substance use disorder, folks can develop tolerance and withdrawal symptoms (e.g., headaches, drowsiness, and difficulty concentrating). Note that those withdrawal symptoms can look a lot like concussion symptoms.
The stimulating benefits and addictive nature are why many folks ritually reach for their cup of coffee every morning - and wonder if they can continue to do so after a concussion.
Theoretical drawbacks of caffeine after concussion/mTBI.
The punchline is that the acute ingestion of caffeine may worsen the glutamate and calcium excitotoxicity of concussion. We don't like that.
Caffeine works by blocking adenosine receptors (e.g., A1 and A2 receptors). A simple and practical example of why this matters is when we consider sleep. As the molecule adenosine builds up throughout the day, it binds adenosine receptors and makes us feel sleepy (i.e., "sleep drive"). So, when we drink coffee with caffeine, it blocks adenosine from binding to its receptors, stimulating us and keeping us from feeling sleepy.
This random image is from “Why We Sleep” by Dr. Matthew Walker
In the context of concussion... Adenosine binds to its A1 receptors, which helps lower glutamate and inflammatory cytokine release. We know that part of the excitotoxicity in concussion is due to an excessive release of glutamate, so adenosine lowering this release could lessen this excitotoxic damage. But, the acute ingestion of caffeine may block these adenosine receptors and dampen the beneficial effects.
Additionally, part of the problem during the excitatory phase of a concussion is the indiscriminate flow of calcium. Calcium ends up "flooding" our mitochondria and dramatically impairing our brain's ability to produce energy (ATP). Caffeine can activate cell messenger systems that increase calcium inside the cell through fancy secondary messenger mechanisms.
Caffeine and return-to-play (RTP) after a sports-related concussion.
Caffeine supplementation (e.g., caffeine pills or coffee consumption) has repeated and known cognitive performance benefits. When looking at concussions specifically, we see improvements in ImPACT scores. The ImPACT test is a computerized neurocognitive test used in baseline testing and by many organizations when making RTP decisions.
While the improvements in reaction time, visual processing, and memory are minor, this may falsely make a player look back to baseline or be ready to play when they are not.
A quick note on chronic consumption of caffeine.
My coffee drinkers may be worried, "But I drink caffeine every day; is that a problem? Would that make a future concussion worse?"
On the contrary, that might be a good thing. Coffee may have legitimate health benefits in average doses of 1-2 cups per day (100-300mg caffeine daily). And from a TBI perspective, we see that chronic caffeine consumption increases your number of adenosine receptors. So, when adenosine is released in a TBI, there are more places to bind and regulate glutamate and calcium release. But, this adenosine release has different effects depending on TBI severity.
Don't confuse severe TBI and mild TBI (concussion).
Research or articles may suggest caffeine's acute benefit in traumatic brain injuries (TBIs). This acute benefit is only seen in severe TBI. In severe TBI, we find benefits from caffeine binding up adenosine receptors. That's because, in severe TBI, so much adenosine can is released, binding so many receptors that it actually slows down your breathing to a lethally slow rate. In these instances, caffeine preventing adenosine from binding its receptor can save your life by preserving your breathing ability. However, severe TBI is significantly different from mild TBI (i.e., concussion).
Quick summary and recap:
We cannot recommend caffeine for concussion recovery, as the evidence doesn't exist, and it may provide falsely good RTP scores. That said, it likely won’t harm your recovery when consumed after the acute period of 24-72 hours.
Caffeine is a stimulant that works by binding/blocking adenosine receptors, and roughly 87% of Americans consume caffeine.
When consumed acutely (minutes to hours) after an mTBI/concussion, it might promote excitotoxicity (bad thing).
When consumed chronically (i.e., regular coffee drinkers), there may be benefits from increased adenosine receptors (good thing) - and we don’t want to block these acutely by consuming caffeine.
The benefits of acute caffeine ingestion seen in severe TBI do not translate to mild TBI (i.e., concussion).
References:
Abalo, R. (2021). Coffee and caffeine consumption for human health. Nutrients, 13(9), 2918.
Lusardi, T. A., Lytle, N. K., Szybala, C., & Boison, D. (2012). Caffeine prevents acute mortality after TBI in rats without increased morbidity. Experimental neurology, 234(1), 161-168.
Lusardi, T. A., Lytle, N. K., Gebril, H. M., & Boison, D. (2020). Effects of Preinjury and Postinjury Exposure to Caffeine in a Rat Model of Traumatic Brain Injury. Journal of Caffeine and Adenosine Research, 10(1), 12-24.
National Research Council. (2001). Caffeine for the sustainment of mental task performance: Formulations for military operations. Washington, DC: National Academy Press, 6, 104-168.
Powers, M. E. (2015). Acute stimulant ingestion and neurocognitive performance in healthy participants. Journal of athletic training, 50(5), 453-459.
Trojian, T. H., Wang, D. H., & Leddy, J. J. (2017). Nutritional supplements for the treatment and prevention of sports-related concussion—evidence still lacking. Current sports medicine reports, 16(4), 247-255.
Website/Database: https://examine.com/supplements/caffeine/