Happy Tuesday!
First, to everyone who responded to my email yesterday about finding an HRT doc, thank you! (click this link to read it in case you missed it)
I have been inundated with hundreds of responses. If you haven’t heard back from me, please be patient. I promise to respond personally to each of you!
Next, I just dropped a new video on Spotify where I go in depth on a topic I’ve been thinking about, testing, and using for years, but haven’t discussed publicly.
It’s on the difference between caffeine, theacrine (TeaCrine®), and paraxanthine.
Most people think the energy conversation begins and ends with coffee. And for a long time, that was true for me too. I love coffee. I still drink it. Usually one cup, sometimes two.
But as I’ve gotten deeper into performance, cognition, longevity, sleep quality, and stress regulation, it became obvious that caffeine isn’t always the best tool for every situation.
There are now cleaner, more precise molecules that let us harness the benefits of caffeine without paying for it later in the form of crashes, anxiety, or poor sleep.
In this email, I’m going to break down:
How caffeine actually works (and why it sometimes backfires)
Why theacrine is one of the most underrated “clean energy” compounds available
Why paraxanthine is essentially caffeine 2.0
How I personally use all three
A clear comparison chart with dosing, pros, and cons
And links to the research if you want to go deeper
Let’s start with the molecule everyone already knows.
Caffeine
Caffeine works primarily by blocking adenosine receptors in the brain. Adenosine is the chemical signal that builds up the longer you’re awake and tells your brain it’s time to rest. Block that signal, and you feel alert.
It also increases dopamine (motivation and reward) and epinephrine/adrenaline (energy and drive). That’s why caffeine feels so effective, and why it can sometimes feel like too much.
The upside is obvious:
Rapid increase in alertness
Improved reaction time and endurance
Increased fat oxidation during exercise
Reliable, inexpensive, and widely studied
The downside shows up when dose, timing, or frequency get out of control:
Jitters and anxiety
Heart rate racing
GI discomfort
Sleep disruption
Tolerance buildup
And the classic spike → crash cycle
About 80% of caffeine’s benefits actually come from its primary metabolite, paraxanthine. The remaining metabolites (theobromine and theophylline) contribute more to side effects than performance.
Caffeine is best used intentionally, not reflexively.
And that’s where alternatives come in.
Theacrine (TeaCrine®)
Theacrine is structurally similar to caffeine and is found naturally in kucha tea, but its effects differ significantly.
This is one of my favorite compounds for people who say:
“I want energy and focus, but I don’t want to feel wired.”
or
“I want something I can use without building tolerance.”
Mechanistically, theacrine:
Antagonizes adenosine receptors
Directly modulates dopamine signaling
Has minimal effect on cortisol and adrenaline
Does not significantly increase heart rate or blood pressure
The subjective effect is what most people notice first.
Instead of a sharp spike, theacrine feels like clean, steady mental energy. Focus improves. Mood improves. Motivation improves. But there’s no jitter, no urgency, no crash.
What really sets theacrine apart is tolerance, or lack thereof.
Human studies show that, even after weeks of daily use, theacrine remains effective at the same dose.
Its long half-life is why a single dose can provide 8–10 hours of sustained energy. Yet interestingly, studies show it does not significantly disrupt sleep, even when taken later in the day.
This makes it incredibly useful for:
Long workdays
Creative or cognitive work
People quitting caffeine
Evening productivity without wrecking sleep
If caffeine is a hammer, theacrine is a dimmer switch.
Paraxanthine
Paraxanthine is caffeine’s primary active metabolite. When you drink coffee, your liver converts most of that caffeine into paraxanthine.
The obvious question is, “Why not take the compound that actually delivers the benefits without the baggage?”
Paraxanthine:
Blocks adenosine efficiently
Enhances dopamine and norepinephrine
Increases fat oxidation
Improves reaction time and cognitive performance
Has a shorter half-life (~3 hours)
Produces less anxiety, less jitter, and less sleep disruption
In head-to-head studies, paraxanthine has:
Improved reaction time more than caffeine
Reduced cognitive errors post-exercise
Lowered perceived exertion during training
Produced cleaner stimulation with fewer side effects
Paraxanthine also bypasses genetic variability in caffeine metabolism. Some people are slow caffeine metabolizers and get hammered by side effects. Paraxanthine removes that variable.
Subjectively, you feel awake, focused, and motivated, yet calm.
No spike.
No crash.
No anxious edge.
This is why I call it caffeine 2.0.
Comparison
Compound | Pros | Cons | Typical Dose |
|---|---|---|---|
Caffeine | Fast onset, strong alertness, fat oxidation, well-studied | Jitters, anxiety, tolerance, sleep disruption, crash | 50–200 mg |
Theacrine | Smooth energy, no tolerance, minimal stress response, sleep-friendly | Slower onset, subtle for stimulant seekers | 100–400 mg |
Paraxanthine | Clean focus, less anxiety, faster clearance, strong performance | Still a stimulant, newer compound | 100–300 mg |
How I personally use them:
Coffee in the morning
Paraxanthine in the afternoon if needed
Theacrine for long days, late work, or caffeine breaks
Final Thoughts
Caffeine works. It always has.
However, Theacrine and paraxanthine represent a shift toward stimulants that:
Support energy without overclocking stress
Preserve sleep
Reduce dependency
And work with your biology instead of against it
If your goal is:
Better focus
Better energy
Better sleep
And better long-term outcomes
Knowing when and how to use these tools can be the edge you need.
If you want the full breakdown, the Spotify video is live now, and I walk through it visually with slides and real-world context.
As always, thank you for supporting my work!
Best,
Hunter Williams
P.S.
Here are my favorite sources of each:
Paraxanthine: https://www.unmatchedsupps.com/products/paraxanthine?sca_ref=8677061.S6mh8SOsogBzjOO (code hunterw for 10% off)
Teacrine: https://a.co/d/03HxUYZ5
Caffeine: https://www.blackwhiteroasters.com/
Further Reading
Caffeine
Adenosine and caffeine mechanisms
Caffeine and circadian rhythm disruption
Theacrine (TeaCrine®)
Theacrine adenosine + dopamine mechanisms (animal model)
8-week human safety + non-habituation (TeaCrine® up to 300 mg/day)
Theacrine + caffeine on performance outcomes (human study)
Paraxanthine
Paraxanthine safety/toxicology comparison vs caffeine (Frontiers in Toxicology)
Paraxanthine vs caffeine after a 10-km run (cognitive function improvement)