I hesitated to write this week's newsletter letter.

I don't intend for this platform to chase trends or report on everything that wellness influencers say. But this recent study is relevant to energy, mood, stress, health, and the fact that Bryan Johnson posted about it means that it's making the rounds.

There seems to be some misinterpretations about the study itself. So let’s demystify some of the underlying foundations and mechanisms that drive the fairly old, but recently popular, phenomenon that is the microbiota–gut–brain axis.

What we call it makes it sound horribly boring, but let's just pause to reflect on how utterly amazing and outrageous it is that bacteria influence our emotions and behavior. Can I let that sit?

If you feel a little weirded out, I would say that's also a normal reaction.

Maybe. Maybe it’s an oversimplification. But at the core of the thing, I’d argue, it’s what we’re finding.

What we mean when we say it’s bacteria is really that these bacteria produce molecules in interaction with its environment. Remember that bacteria are living things, so when they interact with their environment, they are processing these things in some way and they produce what to them might be waste, but to us could be antibiotics or bioplastics or insulin analogues.

In the case of our bodies, its environment is our gut, which means anything we ingest — so our diet — and whatever those bacteria came in on — so their host compounds.

When these bacteria live in our gut, the molecules produced are then released into that space and then systematically into our blood, nerves, immune system, and hormonal systems to influence mood, cognition, and neural inflammation.

And these tiny little molecules have been linked to depression, bipolar disorder, neurodegeneration, Alzheimer's disease, among other things.

Now that that foundational background is taken care of, let's dive in to this study at hand.

This study tracked 62 healthy adults across periods of habitual coffee drinking, abstinence, and the reintroduction of caffeinated or decaffeinated coffee. Their main finding: drinking coffee changes the specific types of bacteria living in your gut.

And the gut bacteria react to the coffee itself, not the caffeine. This means that you will get the health benefits of drinking coffee, regardless of whether you drink caffeinated or decaf.

Impulsivity and emotional reactivity go down. Blood pressure comes down. Inflammatory markers (CRP and TNF-α) go up.

Reduced depression, impulsivity, and perceived stress. Overall, coffee drinkers showed a lower baseline of inflammation.

It didn’t matter whether it was regular or decaf. Both helped.

There is a small nuance in the inflammatory response to decaf coffee that has caused confusion. When drinking decaf, the resting levels of some inflammatory markers (CRP and TNF-α) increased. However, when researchers tested their immune cells against an active bacterial threat, their inflammatory reaction was significantly blunted compared to non-coffee drinkers. This suggests that decaf drinkers are still well-protected against severe inflammation.

The answer: it depends what you're looking for.

Basically, whether drinking coffee regularly is “good” for you depends on your personal health goals.

Ultimately, whether you have a coffee habit or not reshapes the "chemical factory" in your digestive system. It dictates how well you digest food, how you manage stress, how well you sleep, and probably even how you process emotions.

This study was funded in part by the Institute for Scientific Information on Coffee, a coffee-industry-affiliated body. It doesn’t invalidate the findings. The methodology is refreshingly rigorous for a coffee study, but it’s good to have the context in any case.

While rigorous, it’s small at 62 people. That’s often the required trade-off. It’s primarily powered for the microbiome outcomes, not necessarily as much the behavioral ones.

Here are some practical takeaways for your energy this week:

☕ Match your coffee to what you need. Caffeinated for anxiety reduction and attention. Decaf for memory, sleep, and recovery. Both feed your gut microbes.

☕️ Don't underestimate decaf. If you've moved away from caffeine for cycle, sleep, anxiety, or pregnancy reasons, you're not missing the benefits.

🌱 If you're cutting coffee, replace the polyphenols. Cocoa, berries, green tea, and extra virgin olive oil all deliver polyphenols through the same gut-microbe pathway, affecting inflammation.