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When To Take Caffeine During A Marathon

Updated: Mar 29, 2019

90% of us can benefit from using caffeine when we race and plenty of us already do. In a 5 or 10k race it's hard to go to wrong, as the optimal dose is 3-6mg per kilo of body weight and the effects of caffeine should last long enough to see you through the entire race. With recovery so quick, you can race most weeks and afford to experiment as it doesn't matter if your race goes slightly wrong.

However with marathons the stakes are much higher. Requiring months of training and a month of recovery, most of us only race a marathon once or possibly twice a year and some only once ever. Racing for so long the permutations of when you can take caffeine during are vast, so it's crucial that you get your caffeine strategy right to ensure that you don't have a caffeine crash mid-race or hit the wall with a pocketful of caffeine yet to be used. Which leads us to ask:


What Is The Best Caffeine Strategy For A Marathon?


In our blog we have always made a point of starting with scientific studies for our research rather than relying on our own experience or creating a narrative that helps the brand, but for marathons the research is unfortunately limited. It's incredibly hard to properly test significant numbers of athletes and with so many factors involved in a marathon, replicating all conditions across a control group would be far too difficult. Instead we have tried to assess comparable studies and extrapolate, but there are still some unanswered questions.

Does Caffeine Work In Longer Races?


Few caffeine studies have examined the impact of caffeine over periods longer than an hour. A 2016 study[1] gave cyclists caffeine 80 minutes into a 120 minute cycle, before then performing a time trial approx 30 minutes long. 100mg caffeine lead to a 3.8% reduction in time and 200mg a 7.8% reduction, which suggests that taking caffeine towards the end of a race offers the same benefits as in shorter races, which we probably all instinctively knew already. This study doesn't show though whether you can gain the benefit of caffeine throughout a longer race or whether it is possible to dose multiple times and if so which strategy is optimal.


Should You Take Caffeine In The First Half of a Marathon?


One study[2] examined the timing of doses of caffeine in cycling, giving 300mg caffeine to control groups 135, 75 and 20 minutes before a 30 minute time trial and found that only the group who received caffeine 20 minutes before improved verses the placebo group. Caffeine can stay at high levels in the blood for up to four hours, but this suggests that it does not benefit us in performance once it's peaked in our bloodstream, approx after one hour. So taking even a large dose of caffeine before or early on in a marathon may not aid you past the first half.


The main benefits of caffeine during a marathon are that it:

  1. Reduces the perception of pain and fatigue

  2. Releases fat into the bloodstream, reducing glycogen depletion

  3. Increased alertness

So given that during the first half of a marathon you should not experience pain or fatigue, if you are pacing properly, the first benefit of caffeine is of limited use. It is also likely that the increase in alertness and heart rate will cause you to start too quickly.

Reducing glycogen depletion would be beneficial throughout the marathon, preserving energy and potentially helping us to avoid hitting the wall, so if a lower dose of caffeine can achieve that without the huge caffeine rush then we should consider it.


However a study[3] of 98 runners given 30mg caffeine at 4.5, 9 and 13.5km into an 18km run saw no benefit from the caffeine even though the total caffeine in the bloodstream would have accumulated and suggests that glycogen depletion is not significantly reduced in lower doses even if regularly taken or that if it is, it does not lead to better performance.


So it appears there is no real benefit in taking any caffeine early in a marathon.


When to take caffeine during a marathon?


There are frustratingly few studies that examine alternative or repeat dosing strategies for caffeine as it would be extremely useful to understand:

  • Whether repeat dosing of high levels of caffeine can sustain the benefits of caffeine at an optimal level for an extended period without diminishing returns? (Given the recommended daily limit of caffeine is 400mg we don't recommend you try).

  • How long the benefits of caffeine last with different levels of caffeine and how quickly the benefits fade?

  • Whether a gradual increase in doses leading to an accumulation of caffeine in our system can extend the time period for which caffeine is beneficial and build up to an optimal dose accumulated?

We are therefore left basing the following on our industry experience and have observed that:

  • Caffeine takes 5-20 minutes to have an effect and lasts for 40 minutes to an hour

  • Taking a second dose is not as impactful as the first unless taken relatively soon after or unless you increase the initial dose.

Given all of the above we recommend a flexible approach which you can adapt depending on how your race is panning out, as you may start to tire 16 miles in or might hold out past 20. Considering the difference we therefore recommend having the option of a one or two dose strategy:


If you start to tire before 20 miles - take a mid-sized dose of 80-120mg caffeine which will have an impact, but will also allow you to have a second larger dose of 120-200mg when the effects start to fade.


If you start to tire after 20 miles - you are close enough to the finish for one strong dose to see you home, so take your optimal dose[4] of 3-6mg per kilo and know that you can run flat our until the line.

How Quickly Does Caffeine Effect You?


Something to bear in mind when taking caffeine is that the response time is determined by how you consume it. A 2002 study[5] found that if chewed caffeine was absorbed through the mouth and entered the bloodstream in as little as five minutes, whereas caffeine swallowed can take up to 20 minutes. That could be a 1-3 mile difference during the marathon, which is a considerable amount of time to be running tired, so unless you are chewing your caffeine, you may want to use the two dose strategy before you start to tire.


Good luck with your marathon, you can find free marathon training plans here and if you use Caffeine Bullet during your race, tag us on Instagram to be in with a chance of winning some special prizes!


As with all of our articles we always recommend trialing your nutrition in advance of race day and be aware that caffeine effects everyone differently and does not help everyone (as explained in our blog 'Should YOU use caffeine in sport').



About Caffeine Bullet

Caffeine Bullet is a mint chew with 100mg caffeine and 4 types of electrolytes, formulated for athletic performance, to be taken before and during exercise to improve endurance, increase alertness and reduce the perception of pain. Far more convenient and concentrated than a gel, the caffeine is absorbed through your gums, to give you a more pronounced effect up to 4 times faster so that you can train harder and perform better.

[1] https://www.ncbi.nlm.nih.gov/pubmed/27426699

[2] https://www.ncbi.nlm.nih.gov/pubmed/22476164

[3] https://www.ncbi.nlm.nih.gov/pubmed/15795812

[4] https://www.ncbi.nlm.nih.gov/pubmed/9688750/

[5] https://www.ncbi.nlm.nih.gov/pubmed/11839447

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