Caffeine: Friend or Foe For Your Next Personal Best?
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Caffeine: Friend or Foe For Your Next Personal Best?


Caffeine is the most widely consumed psychoactive substance globally, with three-quarters of athletes using the substance in the Olympics. 

There are many different options for athletes when it comes to caffeine that range from coffee, tea, energy drinks, pre-workout supplements to exercise gels and even caffeinated chewing gum. 

Caffeine ingestion is thought to sustain exercise intensity during heavy and intense endurance training, keep athletes mentally focused and lower pain.

But is that the case for everybody? Read on to find out..

Caffeine is not a consistent performance enhancer for all athletes

There is a very wide variation in results from almost all trials investigating caffeine.

One meta analysis (a type of review that pools together all the results of several research studies) using data from 56 different time trials found the percentage time difference on performance was up to 15.9% (1). A pretty significant finding by most athletes' standards, it is fair to say.

So this begs the question: despite three-quarters of elite athletes taking caffeine (2) and large variations in performance, is caffeine an effective performance enhancer for everyone?

It’s in your genes

One gene alone is responsible for about 95% of caffeine metabolism (2). 

The name of this gene is CYP1A2, which encodes an enzyme in the liver that metabolises caffeine. Variants in this gene affect how quickly the body breaks down and clears away caffeine. 

Unfortunately, about 59% of us have a variant in the CYP1A2 gene that leads to the slow metabolism of caffeine.

Want to find out if you have this genetic variant? 



What does this mean?

Fast caffeine metabolisers take between 4-6 hours to lower caffeine levels by half (ie. its half-life). Slow caffeine metabolisers take between 8-10 hours to drop caffeine levels by half (ie. it stays active in their bodies for longer).

Even a small amount of caffeine can keep slow metabolisers up all night and give them unwanted side effects. It’s recommended that slow metabolisers restrict their caffeine intake to no more than 200 milligrams per day, equivalent to about two cups of coffee (although be aware that caffeine content for coffee can range between zero to over 500mg). 

It is also worth noting that the half-life of caffeine in the body can not simply be measured by how stimulated you feel, and may not deliver any real performance benefits for recreational athletes despite ‘feeling’ the effects of caffeine. 

How to personalise your caffeine performance plan

If you’re a fast metaboliser, then you break down caffeine more quickly, so the effects of caffeine should last for a shorter time – which sounds negative, but it may well be that the molecules caffeine is broken down into also improve performance, which means being a fast metaboliser could be beneficial.

Based on current research on caffeine, genes and performance, these are the recommendations (3):

  • AA: "Fast metaboliser", breaks down caffeine quicker, caffeine has less effect on the body. Consume 3-6mg/kg.
  • AC: "Slow metaboliser", breaks down caffeine slower, caffeine has more effect on the body. Consume no more than 200mg/day.
  • CC: "Slow metaboliser", breaks down caffeine slower, caffeine has more effect on the body. Consume no more than 200mg/day.

Differences in our environment also contribute to the inter-individual response to caffeine use. These include smoking, vegetable intake, menstrual cycle stage and training status. 

Differences in how the caffeine is consumed, such as dose, timing, source, all impact how much caffeine improves our performance too.

Interestingly, those that believe caffeine will enhance their performance see a greater performance enhancing effect during exercise than those who don’t (4)!

What does this mean for you?

A lot of it comes down to self-experimentation. If you use caffeine to improve your performance, experiment with different dosages and different timings.

Constant self-experimentation and self-assessment carried out in training enables you to select the caffeine strategy best suited to you, as opposed to the current one-size-fits-all recommendations aimed at the average person; and, as we all know, you’re not average.

So the answer to the question, “Is coffee good for me?” is: “It depends” and “you should probably take a DNA test”.




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