Q2 Science Newsletter
This digest is for educational purposes only. It is not medical advice and is not intended to diagnose, treat, cure, or prevent any disease. Research cited reflects findings at the time of publication. Individual responses to coffee vary. Consult a qualified health professional before making changes to your diet or health routine.
This edition of our newsletter covers seven papers published over the past few months: two cohort studies on coffee and liver disease, a third cohort study on coffee and diabetes, a randomized trial that revisits the long-standing advice to give up coffee with an irregular heartbeat, a precision-nutrition analysis of blood pressure and genetics, a food-science look at what different milks do to the cup, and a wide-ranging review of how coffee's compounds move through the body. None of these settle the science on their own. Read together, though, they add to the big picture puzzle that is coffee, and that is the part I find genuinely useful. Here is what I found.
Your brewing method may matter for liver health, not just how much you drink
One question I keep returning to is whether how we brew matters as much as how much we drink. A cohort study from southern Italy offers a partial answer. Among 1,079 adults in the Nutrihep cohort, higher intake of Italian-style coffee, meaning espresso or moka, was associated with progressively lower odds of MASLD (metabolic dysfunction-associated steatotic liver disease), now the most prevalent chronic liver disease in the world. The odds were lowest among those drinking four to six cups a day. The authors point to unfiltered brewing, which retains more diterpenes and chlorogenic acids than paper-filtered coffee, as a plausible reason. I want to be clear about what this is, though: an observational study. It can show an association, not cause and effect, and people who drink more espresso may differ in other ways the researchers could not fully account for.
| Daily cups | Odds ratio vs <1 cup | Lower odds vs <1 cup |
| 1 cup | 0.479 | ~52% |
| 2 cups | 0.468 | ~53% |
| 3 cups | 0.449 | ~55% |
| 4 to 6 cups | 0.407 | ~59% |
In plain terms, every level of daily coffee intake was tied to roughly half the odds of MASLD compared with drinking less than a cup, with the benefit largest at four to six cups. Because this was a single snapshot in time, it points to a pattern worth noticing, and another piece of the coffee puzzle, rather than a firm conclusion.
Siani M, Bonfiglio C, Bonfrate L, Donghia R, Pastore MN. Italian style coffee consumption and metabolically dysfunctional-associated steatotic liver disease (MASLD): a cohort population study in Southern Italy. Front Nutr. 2026;13:1797230. doi:10.3389/fnut.2026.1797230
What you stir into the cup may matter as much as how much you drink
This one speaks to a question I hear often: does it matter if I sweeten my coffee? In a UK Biobank cohort of 185,437 adults followed for a median of about ten and a half years, unsweetened coffee was associated with a meaningfully lower risk of MASLD, while sugar-sweetened and artificially sweetened coffee were not. The strongest signal was for unsweetened, caffeinated coffee: more than 2.5 servings a day was linked to a 31% lower adjusted risk compared with non-drinkers [HR 0.69; 95% CI 0.58 to 0.82, which shows a hazard ratio of 0.69, thus 31% lower risk than non-drinkers, and because the confidence interval (0.58 to 0.82) stays fully below 1, the reduction is statistically reliable rather than chance]. What I find most notable is that the association held regardless of each person's genetic predisposition to liver disease or their gut-microbe profile, which the researchers accounted for using genetic risk scores. The study cannot tell us that any single component is doing the work, but the pattern points toward the unsweetened, caffeinated cup.
Liu W, Xu X, Chang Q, et al. Different types of sweetened coffee consumption, genetic predictor of gut microbe, and the risk of metabolic dysfunction-associated steatotic liver disease. Nutr J. 2026;25(1):31. doi:10.1186/s12937-026-01289-8
Caffeinated coffee and lower odds of diabetes, with the benefit concentrated in some groups
Staying with metabolic health, a third cohort study looked at coffee and diabetes. Drawing on United States national survey data (NHANES, 2007 to 2018), researchers examined 6,311 women with a pregnancy history, of whom 1,313 had diabetes and 574 had gestational diabetes. Higher caffeinated coffee intake was associated with lower odds of diabetes, and the more caffeine people took in, the lower the odds tended to be, a dose-response pattern. The association was strongest in women with a body mass index of 30 or above and in those who were less physically active. Decaffeinated coffee showed no significant effect here, and there was no link between coffee and gestational diabetes at all. I will flag the limits plainly, as the authors do: this is cross-sectional, so it captures a snapshot rather than tracking people over time and cannot establish cause; coffee intake was self-reported; the sample was women only; and the gestational-diabetes group was small. It is worth noticing that this caffeine-forward signal sits alongside the unsweetened, caffeinated pattern from the liver study above, while the other liver study in this digest found protection holding regardless of caffeine. The honest reading is that the bioactive picture is still being worked out, and no single study settles which component matters most.
Su X, Hu D, Tan J. Association of coffee consumption with diabetes mellitus and gestational diabetes mellitus. Int J Cardiol Cardiovasc Risk Prev. 2026;29:200626. doi:10.1016/j.ijcrp.2026.200626
A randomized trial revisits the old advice to avoid coffee with atrial fibrillation
For years the standard guidance has been that people with atrial fibrillation (AF) should cut out caffeine. The DECAF trial, published in JAMA, tested that assumption directly, which is rare for this question. After cardioversion to restore normal rhythm, 200 adults were randomized to drink at least one cup of caffeinated coffee a day or to abstain from coffee and caffeine entirely for six months, across five hospitals in the United States, Canada, and Australia. Recurrence of AF or atrial flutter was lower in the coffee group than in the abstinence group, with no meaningful difference in adverse events between them. The authors suggest coffee may reasonably be allowed for many patients with AF. I would add the usual cautions: this was a single open-label trial of about one cup a day in people who already drank coffee, and it does not speak to higher doses or other caffeine sources. Even so, it is a real shift, and a welcome example of testing conventional wisdom rather than repeating it.
|
47%
recurrence, coffee group
|
64%
recurrence, abstinence group
|
HR 0.61 (95% CI 0.42 to 0.89) · P = .01
In plain terms: over the six months, about 47% of the coffee drinkers had their atrial fibrillation return, compared with about 64% of those who avoided coffee entirely. The hazard ratio of 0.61 means the coffee group's risk of recurrence was roughly 39% lower, and because the confidence interval (0.42 to 0.89) stays below 1 and the P value is .01, the difference is unlikely to be due to chance.
Wong CX, Cheung CC, Montenegro G, et al. Caffeinated coffee consumption or abstinence to reduce atrial fibrillation: the DECAF randomized clinical trial. JAMA. 2026;335(4):317-325. doi:10.1001/jama.2025.21056
Coffee and blood pressure: your genetics may shape the benefit
If coffee seems to help some people's blood pressure more than others, genetics may be part of the story. Researchers ran genome-wide analyses in two large groups, the Korean KoGES cohort (n=53,114) and the UK Biobank (n=466,925), and built a genetic risk score for hypertension from common variants. Higher coffee and tea intake was associated with lower hypertension risk, but only in people with a lower genetic risk score. In those carrying a higher genetic burden, the association was not significant. This is a gene-diet interaction study, so it is generating hypotheses about personalized nutrition rather than proving that coffee lowers anyone's blood pressure. This may be an early sign that coffee's cardiovascular benefits are greatest for people who do not already have a genetic predisposition to high blood pressure. It is also a reminder that nutrition rarely works the same way for everyone.
Hur HJ, Yang HJ, Kim MJ, Jang HJ, Kim MS, Park S. Precision nutrition for hypertension: tea, coffee, antioxidant vitamins interactions with polygenic risk in multi-ethnic populations. Eur J Clin Nutr. 2026;80(3):307-321. doi:10.1038/s41430-025-01699-7
What different milks do to the compounds in your cup
Here is a practical, in-the-cup question with a food-science answer. Researchers compared whole milk against soy, almond, and coconut, each blended with coffee at three ratios (70:30, 50:50, and 30:70, coffee to milk). Across every milk type, the measured chlorogenic acid and caffeine content dropped as the proportion of milk rose, so the most coffee-forward blends retained the most of these compounds. Beyond that, each milk had its own character, summarized below. Two honest caveats: this study measured what is in the cup, not what those compounds do once they reach the body, and more in the cup does not automatically mean more absorbed.
| Milk type | Standout finding |
| Whole milk | Highest soluble solids (°Brix) and the brightest, whitest cup; most pronounced at coffee-dominant ratios. |
| Almond | Highest total phenolics and antioxidant capacity among the plant-based options, peaking in the 50:50 blend. |
| Soy | Highest viscosity of the group, with solid sensory scores at coffee-dominant ratios. |
| Coconut | Highest overall consumer acceptance among the blends tested, strongest at the coconut-forward 30:70 ratio. |
A reminder worth adding here, since this question comes up so often, is that what happens in the cup is not the whole story, because milk does not only dilute coffee's compounds, it interacts with them. About fifteen years ago, Duarte and Farah looked at this directly in people: when subjects drank coffee with whole milk, they recovered noticeably less chlorogenic acid and its metabolites in the hours afterward than when they drank the same coffee in water, roughly 40 percent of the dose with milk against 68 percent without. That points to milk proteins binding these compounds and lowering how much the body takes up. A later laboratory study by Tagliazucchi and colleagues can look at first like a contradiction: in a simulated digestion, adding milk increased the amount of chlorogenic acid left available, and the more fat the milk contained, the more remained.
The two results are easier to reconcile than they seem, because they measure different things. The laboratory study captures how much is released and stays soluble during digestion, while the human study captures how much a person absorbs and excretes. For the question most of us care about, what reaches the body, the human evidence is the better guide, and there the milk cup came out lower. So the takeaway is not that you should skip the milk, but that "more in the cup" and "more absorbed" are two different questions, and on the evidence we have, adding milk appears to trim the chlorogenic acids your body ends up with.
Oblitas-Delgado R, Meléndez-Mori JB, Mori-Vigo S, et al. Comparative effects of dairy and plant-based milk addition on physicochemical, functional, and sensory properties of coffee beverage. Applied Food Research. 2026;6(1):101926. doi:10.1016/j.afres.2026.101926
The Farah human study: Duarte GS, Farah A. Effect of simultaneous consumption of milk and coffee on chlorogenic acids' bioavailability in humans. J Agric Food Chem. 2011;59(14):7925-7931. doi:10.1021/jf201906p
The more recent in vitro study: Tagliazucchi D, Helal A, Verzelloni E, Conte A. The type and concentration of milk increase the in vitro bioaccessibility of coffee chlorogenic acids. J Agric Food Chem. 2012;60(44):11056-11064. doi:10.1021/jf302694a
A review of what happens to coffee's compounds between the roaster and your body
I appreciate literature reviews, because they help consolidate information with fresh eyes. Writing in Molecules, the authors map the metabolism, bioavailability, and health effects of coffee's major bioactive compounds: chlorogenic acids and their lactone derivatives, melanoidins, trigonelline, caffeine, diterpenes, and N-methylpyridinium. One thread is worth highlighting because it answers a question I get a lot, which is why more antioxidants in the cup does not simply translate to more in your bloodstream. A good share of chlorogenic acids are not absorbed in the small intestine; they travel to the colon, where gut bacteria transform them into other active metabolites. That makes your individual microbiome a real co-factor in how coffee affects you. Because this is a review rather than new trial data, its value is in clarifying the landscape, not in delivering a single new finding.
Finta H, Pál S, Solymár M, et al. Bioactive compounds in coffee: metabolism, bioavailability and health effects. A review. Molecules. 2026;31(9):1404. doi:10.3390/molecules31091404
