I’ve started listening to the BBM podcast recently and I’ve been really enjoying it, lots of good information. I just listened to the BBM podcast on caffeine (episode 197) and something was bugging me about some of the studies cited.
I did a little searching and I found a paper by James & Rogers (2005), “Effects of caffeine on performance and mood: withdrawal reversal is the most plausible explanation”, which talks more about the thing that was bugging me, which they call the “withdrawal reversal hypothesis”. The idea is that a standard RCT design that gives caffeine to habitual users can’t tell if the ergogenic benefit is a “true” benefit or if it’s only happening because taking caffeine reverses caffeine withdrawal symptoms. They claim that the research mostly supports the hypothesis that caffeine only reverses withdrawal symptoms.
I haven’t read most of the studies they cited and this is very far from my area of expertise so I want to know what you think about it. Do you think it’s likely that the benefits of caffeine only or mostly come from reversing withdrawal? Which studies do you think provide the best evidence for/against the withdrawal reversal hypothesis?
Yes, I’m familiar with this paper and so are others, which is why the good studies either use caffeine naive individuals when studying ergogenic benefits or assess performance over a longer period of time such that withdrawal effects do not predominate.
I do not think that the ergogenic benefits of caffeine shown in the literature are solely due to withdrawal reversal, though some study designs certainly have an element of that.
I am fine with the research we cited in that podcast.
I did some searching and found two longer-term studies, Beaumont et al. (2016) and Lara et al. (2019), which administer caffeine for 20+ days to see the effect of habituation. They agree with what you said on the podcast that the ergogenic benefits of caffeine decrease over time but stay above placebo. Do you know of any other longer-term studies like those?
(I briefly looked through the citations on the caffeine BBM podcast and it looks like they’re all either meta-analyses or not relevant (eg studies on cardiovascular health). I didn’t fully read the meta-analyses but it looks like Grgic et al. (2018) focuses on point-in-time performance, not performance over time, and Grgic et al. (2019) says it didn’t look at the effects of caffeine habituation (under the section “Suggestions for future research”).)
The RCTs included in the metas definitely have a few that fit your requirements re: habituation vs naive users as mentioned above. Also some short-term performance over time trials in there as well as I recall.
Yes, I do know of a few longer term studies on caffeine usage and physical performance in a few different populations. While I’d prefer more data of course, we see the same trend and I am less interested in pursuing the topic further. While the effects of habituation are important, I do not think they eliminate or explain the noted ergogenic benefits in whole or large part. Grgic also links some additional commentary on this as well. I’m okay with you spending some more time doing some digging here if you’re interested. Again, I feel very comfortable with what was said on the podcast and research cited.