A cup of coffee in the early morning — most people only care whether it can dispel drowsiness.
But we rarely realize that coffee may influence our mood throughout the day.
Recently, a team from the APC Microbiome Ireland Institute published a study in Nature Communications, “Habitual coffee consumption is linked to differences in gut microbiota and gut physiology,” revealing a hidden pathway between coffee and the human body: the microbiota–gut–brain axis.
Once coffee enters the body, it directionally regulates specific gut bacteria and metabolites, linking mood, cognitive ability, and immune status along the way.
Interestingly, caffeinated and decaffeinated coffee act on different targets.
This study did not limit itself to caffeine as a single component.
Comparing samples from people who drink regular coffee versus decaf over the long term, the team found that coffee’s shaping of the gut microbiota does not come entirely from caffeine.
Both types of coffee can alter gut flora composition and regulate gut physiology, but their respective advantages diverge.
Caffeinated coffee leans more toward rapid neural and immune regulation.
Caffeine itself can stimulate gut microbes to synthesize specific metabolites that send signals via the gut–brain axis, participating in the regulation of neural excitability — the familiar “pick-me-up” effect — while mildly modulating the body’s immune response.
Decaffeinated coffee, by contrast, relies more on non-caffeine active compounds such as polyphenols and dietary fiber.
These components continuously nourish specific beneficial bacteria and stabilize the gut barrier, producing a more long-acting effect that stands out in metabolic homeostasis and the maintenance of the gut micro-ecology, persistently reshaping the gut environment without depending on caffeine.

In short, coffee is not simply “stimulating the brain” — it first acts as a fine-tuner of the gut.
The gut microbiota receive the various active compounds in coffee, generate metabolic signals, and then transmit them upward along the gut–brain axis to the central nervous system, ultimately reflected in our mood swings and changes in focus.
This also explains why some people, after drinking coffee, feel not only alert but also emotionally uplifted, while others easily become anxious and sensitive.
Individual differences in gut microbiota are an important reason.

Of course, the study only proves an association between habitual coffee intake and the gut microbiota and gut physiology — it does not mean drinking coffee can directly treat mood or immune diseases.
Changes in the microbiota are a complex chain reaction; everyone’s gut baseline differs, so responses to coffee vary widely.
References:
https://www.sciencedirect.com/science/article/pii/S3051172026000149
Reprint Notice & Disclaimer
- This article is edited and compiled by coffeeyo.com and reprinted from the original source. The original copyright belongs to the original author. This reprint is for coffee-industry information sharing only and does not represent the site’s position; all data and views are subject to the original. We thank the original author for their work and sharing.
- Original: Original source
- If you have questions regarding authorization, attribution, copyright, or any other matter, please contact us promptly and we will verify and cooperate. We also welcome coffee companies and industry media to exchange story leads with us.
- Contact coffeeyo.com: Tel 400-0000-641 (+86-18288016826) | Email 405854472@qq.com | Address: Jinghong City, Xishuangbanna, Yunnan Province



