Caffeine as a Testosterone Booster? 70% Increase in the Big T Without Concomitant Performance Benefits, Though

I am curious if caffeine gum producers will start marketing them as testosterone boosters, now. People's willingness to waste money on temporary increases of a figure on their labwork is amazing, after all.
It has been a while that I've dissected a "testosterone booster"; for a good reason, that is. After all, there's no convincing evidence that a 40% increase in natural testosterone levels will have any effect on the way you look or perform. So, even if you happen to find a product that will actually work, your chances that you will get a return on that investment are... well, more jacked than that T-booster is going to get you ;-)

With that being said, I will, obviously, make an exception from the "ignore the monthly T-booster study"-rule and intend to cover the results of a recent study by scientists from the Leeds Trinity University. Why is that? Well, it's about a testosterone booster most of you are already using, anyway.
You can learn more about coffee and caffeine at the SuppVersity

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Coffee Brewing 101 (Optimal Health)

Quantifying the Benefits of Caffeine on Ex.
As a SuppVersity reader, you will remember that the study at hand, in which Reynolds et al. tested the effects of chewing caffeine gum (CAF: 400 mg; 4.1 ± 0.5 mg/kg) or a placebo gum for five minutes on the performance and hormonal response to exercise, is by no means the first study to suggest that the 'right' dosage of caffeine can promote the exercise-induced increase in testosterone.
Figure 1: We do have good evidence that high dose caffeine can be too much of a good thing... at least if you measure "good thing" via the testosterone to cortisol ratio which will decrease after 800 mg by 14%; ± 21% (Beaven. 2008).
I fact, caffeine increases testosterone dose-dependently, albeit with a concomitantly augmented increase in cortisol of which broscience indicates that it would counter the additional increase in "T" Beaven et al. observed with 800mg vs. 400mg of caffeine.

I am not sure if Reynolds et al. were aware of Beaven's previously discussed paper (see Figure 1), but with 400mg per gum, the UK-based scientists nailed what's probably the optimal dosage.

In their study, the scientists aimed at investigating the use of caffeinated gums during half-time in team on sports physiological (blood lactate, salivary hormone concentrations) and performance (repeated sprints, cognitive function) parameters.
Yes, I do suggest that it may be beneficial to drink these two and another two cups of coffee w/ lots of sugar after your workout - if you are an athlete, at least | more.
Another new study confirms: Caffeine is a nutrient muscle-specific repartitioner. While caffeine has gotten a bad rep for promoting insulin resistance, it obviously doesn't do that in muscle. You will remember that several studies have shown that a post-workout coffee can speed up glycogen recovery and, most recently, scientists from the High Point University came one step closer to explain the mechanism. In their study, they bathed myotubes in physiological levels of caffeine and found significant increases in GLUT4 (that's the glucose transporter) expression, glucose uptake and overall cell metabolism through mechanisms partially dependent on PPAR╬▓/╬┤ (Schnuck 2017).
To this ends, Reynolds et al. recruited players from the professional academy rugby union (n=14) for a double-blind, randomized, counterbalanced study.
" Following pre-exercise measurements , players chewed a placebo (PL) gum for five min before a standardized warm-up and completing repeated sprint testing (RSSA1). Thereafter, during a 15 min simulated half-time period, players chewed either caffeine (CAF: 400 mg; 4.1 ± 0.5 mg·kg-1) or PL gum for five min before completing a second repeated sprint test (RSSA2)" (Reynolds 2017).
Much to their own surprise, the authors did not record significant effects on either reaction time or exercise performance (40m sprint times).
Figure 2: Mean ± SD salivary testosterone (large panel) concentrations throughout the caffeine (CAF; dashed line, black markers) and placebo (PLA; solid line, hollow markers) gum trials and individual half-time responses to the CAF trial (dashed line represents mean response). Shaded region = timing of gum intake (Reynolds 2017).
The salivary testosterone levels, on the other hand, went through the roof... for the short period of time between the first and the second sprint test, that is and - as previously pointed out - alongside significant, albeit non-caffeine dependent increases in cortisol levels.
Hypothetical serum testosterone levels in the course of the first seven days after the injection of endogenous testosterone (blue) compared to the regular diurnal rhythm (green) and the levels in response to a pretty potent (+70%) natural testosterone booster (red; all data has illustrative value, only)
Putting things into perspective: The transient nature of the T-elevation is yet not the only reason to doubt why "practitioners [would even seek] enhancing testosterone concentrations" (Reynolds 2017) in this way. Even with "[f]urther research" of which the authors say that it "is required to optimize the use of caffeinated gums (e.g., dose, timing etc.) during the half-time period. It is unlikely that the concomitant increase in testosterone - as pronounced as it may be - has any relevant physiological effects. The effect on bioavailable T is, after all, fundamentally different from what you'd see with the injection of gear... but I've discussed that in enough detail in my article series on building muscle; so I'll simply refer you to the corresponding article | Comment!
  • Beaven, C. Martyn, et al. "Dose effect of caffeine on testosterone and cortisol responses to resistance exercise." International journal of sport nutrition and exercise metabolism 18.2 (2008): 131.
  • Russell, M., et al. "The Physiological and Performance Effects of Caffeine Gum Consumed During A Simulated Half-Time By Professional Academy Rugby Union Players." The Journal of Strength & Conditioning Research (2017).
  • Schnuck, J.K., Gould, L.M., Parry, H.A. et al. "Metabolic effects of physiological levels of caffeine in myotubes." J Physiol Biochem (2017).
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