Coffee, heart rhythms, steps, sleep and blood sugar in 100 adults
What it found
Drinking caffeinated coffee did not change one type of extra heartbeat but was linked to more of another type, more daily steps and less sleep.
Blood sugar stayed about the same on coffee days and non-coffee days in 100 adults.
What they found
Studies in people
Extra upper heartbeats
On coffee days, people averaged 58 premature atrial contractions per day compared with 53 on days without caffeine. The authors found no meaningful difference between these numbers.
Extra lower heartbeats
People averaged 154 premature ventricular contractions per day when drinking coffee and 102 when avoiding caffeine. This increase was mainly seen in those who drank more than one cup a day.
Daily steps
Participants took an average of 10,646 steps on coffee days and 9665 steps on days they avoided caffeine. That is roughly 1000 more steps per day when assigned to drink coffee.
Nightly sleep
People slept an average of 397 minutes on coffee nights compared with 432 minutes on nights after avoiding caffeine. Drinking more coffee was linked to less sleep.
Blood sugar levels
Average daily blood sugar was 95 mg per deciliter on coffee days and 96 mg per deciliter on days without caffeine. The authors found no link between coffee and blood sugar changes.
What the authors conclude
- They found that drinking caffeinated coffee did not increase the number of premature atrial contractions in healthy adults.
- Their secondary results suggest coffee may be linked to more premature ventricular contractions, more physical activity and less sleep, though these findings need further study.
- They advise that doctors and patients could use this information to tailor coffee habits to individual health goals.
How it was done
People are often told to avoid coffee because it might cause irregular heartbeats, but the evidence for that warning is mixed. The authors wanted to test what happens when healthy adults drink or skip coffee in their everyday lives.
The researchers followed 100 healthy adults for 14 days. Each person wore a heart monitor, a step counter and a continuous blood sugar sensor. Daily text messages randomly told them whether to drink caffeinated coffee or avoid caffeine that day.
What it can’t tell you
- The trial lasted only 14 days, so it cannot show the long-term effects of coffee on the heart or overall health.
- The participants were relatively young and healthy, so the results may not apply to older adults or people with existing heart conditions.
- Because the trial was not blinded, other habits that changed alongside coffee drinking might explain some of the results.
Who paid
- Funding
- Funded by NIBIB NIH HHS; NHLBI NIH HHS; University of California, San Francisco (from the PubMed record).
- Authors work at
- University of California, Irvine (C.F.); and the University of California, T.J.
The paper
- Title
- Acute Effects of Coffee Consumption on Health among Ambulatory Adults
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Marcus GM, Rosenthal DG, Nah G, et al (2023). Acute Effects of Coffee Consumption on Health among Ambulatory Adults. The New England journal of medicine. doi:10.1056/NEJMoa2204737Free full textPubMed 36947466DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error