Many of us know the feeling: that first cup of the morning gets things moving. Coffee clearly does something to digestion. And because so many people drink it every day, researchers have also asked what it might mean for the brain over the long term.
This article covers both ends: what studies found about coffee and the digestive system, and what they found about coffee and the brain, including mood. We'll be clear about which findings are solid, which are early, and which are mixed.
As always, these are mostly observational findings about coffee drinking in general. They aren't proof of cause, they aren't claims about Edge Coffee, and they aren't a substitute for medical care.
Part 1: Coffee and the digestive system
What coffee does along the gut
A 2022 narrative review pulled together research on coffee's effects throughout the gastrointestinal tract. The author concluded that some effects seem fairly clear: coffee stimulates gastric acid secretion, stimulates bile and pancreatic secretion, stimulates colon motility, and is linked to changes in gut microbiota composition (Nehlig, Nutrients 2022).
Other questions are still debated, including whether coffee affects reflux, peptic ulcers, or inflammatory bowel conditions (Nehlig, 2022). So if coffee bothers your stomach, that's real for you, even if the population research isn't settled.
One transparency note: the review's author disclosed she is a scientific consultant to a coffee-industry research institute, which commissioned the review but, per the disclosure, had no role in preparing it.
Gallstones: a consistent dose-response pattern
One of the clearer digestive findings involves gallstones. A dose-response meta-analysis found that drinking 2, 4, and 6 cups a day was associated with about 11%, 19%, and 25% lower risk of gallstone disease, respectively (Zhang et al., Aliment Pharmacol Ther 2015). The 2022 review also listed reduced gallstone risk among coffee's clearer digestive associations (Nehlig, 2022), though the underlying studies are observational.
Coffee polyphenols and your gut microbes
Coffee contains chlorogenic acids, a family of polyphenols. Research shows they're only partly absorbed. Much of the rest reaches the colon, where gut microbes convert it into other phenolic metabolites. In lab studies, some of those metabolites showed anti-inflammatory activity (Del Rio et al., Nutrients 2010).
That's early, mostly mechanistic science, and lab results don't automatically translate to people. But it's a fascinating example of how coffee interacts with the gut, and one possible reason decaf shares some associations with regular coffee.
Sidebar: kidneys
A meta-analysis of 4 cohort studies with about 25,800 people found that coffee drinkers had about 13% lower risk of developing chronic kidney disease (Srithongkul & Ungprasert, Eur J Intern Med 2020). With only four studies, this is a modest evidence base, so consider it interesting rather than settled.
Part 2: Coffee and the brain
Stroke and dementia
In the UK Biobank, researchers followed about 365,000 adults. Drinking coffee and tea, alone or in combination, was associated with lower risk of stroke and dementia. Drinking 3–6 combined cups a day was associated with lower risk of dementia after a stroke (Zhang et al., PLoS Med 2021).
The broader evidence on dementia, though, is mixed. One meta-analysis found no overall link between coffee and dementia or cognitive decline (Liu et al., Nutrition 2016), while another reported fewer cognitive disorders among moderate coffee drinkers (Wu et al., Clin Nutr 2017).
Where more coffee was linked to worse brain findings
Here's an important counterpoint. A separate UK Biobank analysis found that drinking more than 6 cups a day was associated with 53% higher odds of dementia compared with 1–2 cups a day, along with smaller brain volumes (Pham et al., Nutr Neurosci 2022). For the brain, moderate looks better than heavy.
Mood
Some research has linked regular coffee drinking with lower depression risk (Wang et al., Aust N Z J Psychiatry 2016). That meta-analysis included cross-sectional studies, so it can't show which came first.
A 2025 systematic review and meta-analysis of 17 studies looked at an even more serious outcome. Coffee intake was associated with lower odds of suicidal thoughts and attempts, while energy drink consumption was associated with higher odds (Low et al., Nutrients 2025). The authors stressed that more research is needed to understand the psychosocial factors and whether any of this is causal.
To be completely clear: coffee is not a substitute for mental health care, and none of these findings suggest otherwise. If you're struggling, please reach out to a mental health professional or someone you trust. In the US, you can call or text 988 to reach the Suicide & Crisis Lifeline.
⚠️ Caution box: pregnancy and high caffeine intake
- Pregnancy. In a dose-response meta-analysis of prospective studies, each additional 100 mg of caffeine a day during pregnancy (around one cup of coffee) was associated with a 13% higher risk of low birth weight (Chen et al., BMC Med 2014). A second meta-analysis linked each additional 100 mg a day with about 7% higher risk of pregnancy loss; the authors called the evidence inconclusive but said avoiding high caffeine intake in pregnancy "appears prudent" (Chen et al., Public Health Nutr 2016). One review goes further and argues for avoiding caffeine in pregnancy, a position that remains debated (James, BMJ Evid Based Med 2021). If you're pregnant or trying to conceive, talk with your clinician about caffeine.
- Very high intake. In a UK Biobank analysis, drinking more than 6 cups a day was associated with 53% higher odds of dementia compared with 1–2 cups a day, along with smaller brain volumes (Pham et al., Nutr Neurosci 2022). More is not automatically better.
- Caffeine affects people differently. If you're sensitive, take medication, or have a health condition, check with your clinician. Want the ritual with much less caffeine? Try All Day Decaf.
Practical takeaways
- If coffee gets your gut moving, that fits what research describes (Nehlig, 2022). If it upsets your stomach, try a smaller cup, and talk with your clinician if it persists.
- For gallstones and the brain, the associations favor moderate intake. Very high intake (6+ cups) was linked to worse brain findings (Zhang et al., 2015; Pham et al., 2022).
- Coffee and energy drinks aren't interchangeable in the mood research (Low et al., 2025).
- Quality is your call. If you drink coffee daily, choose beans you trust.
Our approach at Edge
We roast specialty-grade, USDA Certified Organic, shade-grown beans from Peru's highlands and use third-party lab testing for mold and mycotoxins, because a daily ritual deserves a clean cup. See how we test and read about our coffee.
Shop Pure Health Coffee, All Day Decaf, or the full collection.
FAQ
Why does coffee make me need the bathroom? Research describes coffee as stimulating colon motility along with bile and pancreatic secretion (Nehlig, 2022).
Is coffee linked to gallstones? Studies associate coffee drinking with lower gallstone disease risk, about 19% lower at 4 cups a day (Zhang et al., 2015).
Is coffee good for brain health? The evidence is mixed. Moderate coffee and tea drinking was associated with lower stroke and dementia risk in one large study (Zhang et al., 2021), but more than 6 cups a day was linked to higher dementia odds in another (Pham et al., 2022).
Does coffee affect the gut microbiome? Coffee is linked to changes in gut microbiota composition, and microbes convert coffee's chlorogenic acids into other compounds (Nehlig, 2022; Del Rio et al., 2010). This research is still early.
General information about coffee research. Not medical advice. These findings describe coffee drinking in general and are not claims about Edge Coffee.
Sources
- Nehlig A. Nutrients. 2022. https://pubmed.ncbi.nlm.nih.gov/35057580/ (doi:10.3390/nu14020399)
- Zhang YP et al. Aliment Pharmacol Ther. 2015. https://pubmed.ncbi.nlm.nih.gov/26198295/ (doi:10.1111/apt.13328)
- Del Rio D et al. Nutrients. 2010. https://pubmed.ncbi.nlm.nih.gov/22254058/ (doi:10.3390/nu2080820)
- Srithongkul T & Ungprasert P. Eur J Intern Med. 2020. https://pubmed.ncbi.nlm.nih.gov/32317238/ (doi:10.1016/j.ejim.2020.04.018)
- Zhang Y et al. PLoS Med. 2021. https://pubmed.ncbi.nlm.nih.gov/34784347/ (doi:10.1371/journal.pmed.1003830)
- Liu QP et al. Nutrition. 2016. https://pubmed.ncbi.nlm.nih.gov/26944757/
- Wu L et al. Clin Nutr. 2017. https://pubmed.ncbi.nlm.nih.gov/27288328/
- Pham K et al. Nutr Neurosci. 2022. https://pubmed.ncbi.nlm.nih.gov/34165394/ (doi:10.1080/1028415X.2021.1945858)
- Wang L et al. Aust N Z J Psychiatry. 2016. https://pubmed.ncbi.nlm.nih.gov/26339067/
- Low CE et al. Nutrients. 2025. https://pubmed.ncbi.nlm.nih.gov/40507181/ (doi:10.3390/nu17111911)
- Chen LW et al. BMC Med. 2014. https://pubmed.ncbi.nlm.nih.gov/25238871/
- Chen LW et al. Public Health Nutr. 2016. https://pubmed.ncbi.nlm.nih.gov/26329421/
- James JE. BMJ Evid Based Med. 2021. https://pubmed.ncbi.nlm.nih.gov/32843532/