Can Caffeine Increase Testosterone? We Take a Look at the Research
For some, a cup of strong coffee or pre-workout on the way to the gym is as essential as remembering their headphones. The benefits of caffeine for training performance have long been researched and proven effective, but could caffeine also boost testosterone?
A particular piece of research on the topic has been circulating on social media, sparking debate about whether caffeine could positively or negatively affect testosterone levels. The study, although now quite old, explores whether caffeine can help athletes train harder, especially when they haven't had enough sleep.
The study, published in Human Kinetics, gathered 16 professional rugby players who took either a placebo or a caffeine dose of 4 mg per kg of body weight, one hour before exercising. The athletes were categorised as either:
Well rested (8 hours of sleep or more)
Sleep deprived (6 hours sleep or less)
The training included four sets of bench press, squats, and bent-over rows, using 85% of their max weight for one rep. They aimed to complete as many reps as possible without failing.
Saliva samples were collected before taking the placebo or caffeine, and again before and directly after the workout to measure testosterone and cortisol levels.
The study found that sleep deprivation led to a significant decrease in the total amount of weight lifted. In well-rested athletes, caffeine intake caused a moderate increase in the total weight lifted, while the increase was even greater in sleep-deprived athletes, bringing their performance close to that of the well-rested group who took the placebo. Among the athletes, eight were identified as "caffeine responders," showing a notable performance boost from caffeine. Well-rested athletes had higher baseline testosterone levels and slightly lower cortisol levels.
Changes in hormone levels from before taking the dose to just before exercise were linked to how each athlete responded to caffeine. The testosterone response during exercise was higher with caffeine compared to the placebo, and cortisol levels also increased.
The researchers concluded that caffeine can enhance the voluntary workload of athletes, especially when they are tired from lack of sleep. This suggests that caffeine may be beneficial for athletes looking to improve performance under fatigue, particularly for those who respond well to it.
The Verdict
Looking at the effects of caffeine on testosterone, it's difficult to draw solid conclusions from this study for several reasons. Firstly, the primary focus of the study was to examine the effect of caffeine on the lifting performance of athletes during sleep deprivation. Testosterone and cortisol levels were measured, but the primary outcome was not the hormonal response – it was the workload performance. Additionally, the sample size was fairly small to draw robust conclusions from, with only 16 participants, 8 of whom were identified as "caffeine responders."
Multiple studies support that testosterone naturally increases in response to resistance exercise. The rise in testosterone seen in this study could be due to a combined effect of caffeine and exercise, making it difficult to isolate the specific impact of caffeine on testosterone. Caffeine has been proven to be an ergogenic aid for exercise, so the boost in performance could indirectly influence testosterone levels as well.
The study has too many limitations to draw solid conclusions regarding caffeine's effect on testosterone. New research shows that caffeine can even affect our sleep quality up to 12 hours after consumption. While the effects of caffeine can vary among individuals, it could potentially have a knock-on effect on our training performance if we are fatigued from reduced sleep quality, leading to a need for more caffeine in subsequent days. However, this doesn't mean the original study is useless – it could pave the way for future large-scale research and provide insights into caffeine's effects on sleep-deprived training.
What's important to understand from the widespread use of this study on social media is that not all studies are reliable or created equal, and they can be used in ways they weren't originally intended. It's common for social media users to cherry-pick studies to suit their biases. Confirmation bias (when we find research that supports our beliefs) can feel validating, but it's essential to approach all research with an open mind.
A more recent 2022 study published in Nutrition Journal examined the long-term effects of caffeine on testosterone. It found that caffeine intake may contribute to lower testosterone levels, though the relationship is complex. The findings suggest that caffeine could play a role in low testosterone and reproductive health issues, but like the older study, more research is needed.
Until more research is conducted, we can safely conclude that caffeine is a reliable ergogenic aid and will boost resistance training performance at the correct doses, which could potentially have a positive knock-on effect on testosterone production. However, it's important to note that individual responses to caffeine may vary, and we should consume it in appropriate amounts, with a significant gap before bedtime, to avoid its negative effects on sleep quality.
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