Overview
- A 63‑person, blinded reintroduction trial published in late September found that after a two‑week coffee washout and 21 days of resumed drinking, participants reported lower perceived stress, depression and impulsivity.
- Both caffeinated and decaffeinated coffee were associated with measurable shifts in specific gut bacteria and urine or stool metabolites rather than a broad rise in overall microbial diversity.
- The two coffee types showed different behavioral links: caffeinated coffee correlated with reduced anxiety and better attention, while decaf was tied to gains in learning, episodic memory, sleep quality and physical activity.
- Researchers identified changes in microbes such as Eggerthella species, Cryptobacterium curtum and members of the Firmicutes group, and noted some metabolites appeared to come from coffee compounds processed by gut bacteria.
- The study is short and small, relies partly on self‑reported measures, and was sponsored by the Institute for Scientific Information on Coffee, so independent, longer trials are needed before claiming health benefits or causation.