As we have mentioned on previous occasions, caffeine is one of the supplements with stronger
scientific support regarding its effectiveness. Among other mechanisms, caffeine can
improve performance by increasing the activation of the nervous system, increasing the
production of catecholamines and endorphins, thus increasing muscle activation. 1 On the other
hand, caffeine could decrease the sensation of “pain” or suffering caused by high-intensity
exercise, thus improving tolerance to it. These and other processes mean that
caffeine has been shown to be beneficial in very different sports, improving performance by an average
of 3-4% in both endurance tests 2 and tests of strength or muscular
power. 3,4
However, despite its overall effectiveness, until relatively recently it was unknown whether it could
benefit all people equally, or even have negative effects in certain cases. In
this regard, a systematic review concluded that there is great variability in the effects of
caffeine among subjects, which ranged between 0 and 17% improvement. 5
Various factors have been proposed as possible mediators of responses to caffeine.
One of these factors is how accustomed we are to its consumption, because people who
habitually consume caffeine may experience smaller effects than those who are not
accustomed to it. However, a recent study showed that the consumption of 6 mg/kg of caffeine
improved performance in a time trial even in those who usually consumed
high doses (the equivalent of 3 coffees daily). 6
On the other hand, it has also been suggested that certain people could have a weaker biological
response to caffeine consumption, being considered 'non-responders' (for example,
people who consume caffeine and do not experience a sharp rise in blood pressure or do not increase the
release of epinephrine, something that does normally occur in the so-called 'responders').
In this regard, a study divided football players into 'responders' or 'non-responders'
based on their biological response to the consumption of 6 mg/kg of caffeine, and
then performed a series of physical tests including running and jumping. 7 The results
showed that caffeine improved performance practically in the same way in
players classified as 'responders' and 'non-responders'.
As in any field, another factor that could condition the individual response to
caffeine is genetics. Thus, by looking at the genes (specifically the CYP1A gene) we can
distinguish what we would call fast or slow metabolizers, the latter being those in whom
caffeine remains longer in the body and who are more likely to develop
adverse effects after the intake of large doses of caffeine. 8 In this regard, a recent study
observed that the intake of 3 mg/kg of caffeine produced the same benefits across several
strength and power tests in fast and slow metabolizers. 9 Also, another gene
that has been proposed as a determinant of being a “non-responder” to caffeine is ADORA2A,
although a recent study shows that at least 84% of people who would be
considered 'non-responders' according to this gene obtain performance benefits
after the intake of 3 mg/kg of caffeine. 10
Finally, it has been suggested that some people might not have benefit from
caffeine on some occasions but benefit on others. This could explain the high variability
in the responses to caffeine, although under this hypothesis, everyone would eventually be a
'responder' on some occasion. To answer this question, a study evaluated the effect of
taking 3 mg/kg of caffeine on 8 different occasions in the same participants, and the
results showed that all participants improved their performance (1-9% depending
on the test) in at least 3 of the 8 visits compared to the intake of a placebo. 11 Thus, these
results show that even people who at a given moment may be considered “non-
responders” could benefit from caffeine intake on the following occasions.
Conclusions
Caffeine is one of the supplements with the most evidence regarding its benefits in
performance, and as we show in this article, it is beneficial for practically every
world almost independently of genetics or how accustomed we are to it
consumption. In fact, even people who at some point do not gain benefits from their
consumption, they could obtain them on following occasions.
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