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Dr. Gregory Marcus, Associate Chief of Cardiology for Research at UCSF Health

We chat with Dr. Gregory Marcus about the DECAF and CRAVE clinical trials, and the resulting data on how coffee engages with, and impacts, the human body.

Dr. Gregory Marcus, Associate Chief of Cardiology for Research at UCSF Health

Full video posted below, or watch and/or listen to Coffee People on:
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What: Associate Chief of Cardiology for Research & Associate Editor at JAMA
Where: University of California-San Francisco Health
What they order: Cappuccino
Find online: There is along list of clinical trials and publications Dr. Marcus has been involved in recorded on his UCSF profile page. You'll find several that are more specific to coffee curated below. This is the article that led me to this conversation: Acute Effects of Coffee Consumption on Health among Ambulatory Adults.

And a recap of the article in the UCSF news blog: https://www.ucsf.edu/news/2025/11/431036/coffee-safe-for-a-fib⁠

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Dr. Gregory Marcus is the Associate Chief of Cardiology for Research at UCSF Health and an Associate Editor of JAMA. JAMA is an international peer-reviewed general medical journal published online daily and in print weekly. He joined Coffee People when I reached out to him after reading his co-authored paper ⁠Acute Effects of Coffee Consumption on Health among Ambulatory Adults⁠ (2023).

In it, I read the following line:

"CONCLUSIONS: In this randomized trial, the consumption of caffeinated coffee did not result in significantly more daily premature atrial contractions than the avoidance of caffeine."

It felt very relevant to my life (and that of our audience), considering I drink copious amounts of coffee. In this podcast, we chat about how the Doc's later-in-life appreciation for coffee turned into research efforts focused on how beverages like coffee and alcohol engage with and impact the human body.

KEY TAKEAWAYS FROM THE POD

  • Dr. Marcus is a practicing cardiologist, but a lot of his time is spent doing research on how the heart and related body systems engage with popular beverages, like coffee and alcohol.
    • DECAF - Clinical trial studying fibrillation from the upper and lower regions of the heart.
    • CRAVE - Participants were assigned to drink or not drink coffee day-to-day
    • What is a clinical trial? There are observational and interventional clinical studies. Most research falls into the category of observational. A researcher observes and record results. It is useful, easier to do, but prone to "confounding." Essentially, not accounting for all the variables that may be the cause of the result. Statistics can help adjust for the confounders, but it is an imperfect system designed without knowing for certain what the variables are. Alternatively, a randomly assigned study or clinical trial where the variables are introduced intentionally and strategically allows for a more specific result. 
  • It used to be the norm to suggest that patients with heart concerns avoid caffeine and coffee. The CRAVE and DECAF studies resulted in data that countered that advice.
  • Research studies—observational and clinical trials—require Institutional Review Board (IRB) committee approvals. They review study proposals to give the go-ahead under the banner of the supporting institution, like a hospital or university. Without approval, researchers cannot enroll participants. Proposals include drafting and refining consent forms for participants so that they are providing informed consent to participate. 
  • Observational studies need IRB approvals, but less consent because researchers are not imposing a variable on the participant. They are looking backward to see what happens. They are more affordable and easier to launch, but the results are less impactful. Researchers have less control over the variables making it a less valuable methodology. Observational studies are more hypothesis driven efforts. A hypothesis is made and some observations support the hypothesis. A clinical study allows for an X impact to create and/or cause Y result.*
  • Funding can be a challenge for clinical trials. Historically, they can receive support from the National Institutes of Health (NIH) which, theoretically, has no vested interest in the outcome. Industry-provided funding is also available, but can create conflicts of interest. The funders have a result they hope to achieve, which can create bias. There are also funding opportunities from non-profits and private donors.
  • Things are often oversimplified in headlines for the lay audience. The simplifications may skew the results to fit a narrative.
  • Scientists and researchers should welcome being critiqued. Critiques aren't personal attacks. They are value-added details that allow for an expansion (or narrowing) of the theory or hypothesis.
  • It is important to find balance outside of work to be the most efficient and effective version of yourself. 
  • Caffe Central in the UCSF library is his favorite coffee shop.
  • Support clinical research by being a research participant! There is always a need. In my 20's, I participated in a brain-research study at the University of Madison-Wisconsin. I'd like to say it was because of some sort of altruistic reason, but really, I think I was paid $50 and given a printed image of my brain.

    More recently, I participated in a trial studying the brains response to various types of imagery (or at least that's what I think it was). They also paid a small stipend, but more importantly, for a middle-ager like myself, I received another scan of my brain, which could be compared to the first one. So far...so good on brain health!

*I'm not a science guy. This was how I understood it. If there is a more accurate representation of a observation vs clinical trials, please let me know know!

A CURATED LIST OF PUBLICATIONS

From: ⁠https://ucsfhealthcardiology.ucsf.edu/people/gregory-marcus

NATIONAL INSTITUTES OF HEALTH (NIH)

NIH funding has been dramatically cut under the current U.S. Presidential administration. 40% proposed cuts in funding over the past year and an additional proposed cut for 2027.* The cuts are despite widespread public support for the federal funding of medical research, not to mention bipartisan congressional support.

It makes sense. We all have someone in our lives who has been impacted directly by a disease that these funds are used to study and potentially solve. Think cancer, liver diseases, immune deficiencies, etc. The impact is immeasurable, though the institute tries!

NIH-supported research on drug development for eye diseases has saved $28.5 billion in health care costs over 10 years and reduced wet age-related macular degeneration (AMD)-related legal blindness by 50%.
• NIH.gov
Research-related gains in average life expectancy, including those supported by NIH, have an estimated economic impact of approximately $38 trillion per year of extended life.
• NIH.gov

The NIH's stated mission is to "seek fundamental knowledge about the nature and behavior of living systems and the application of that knowledge to enhance health, lengthen life, and reduce illness and disability." It's heady big-picture stuff.

There are currently 403 listed grant opportunities listed on NIH.gov. With cuts as much as 2.7 billion dollars in just the first quarter of 2026, it is likely some (or many) won't be funded. Support for (and from) the NIH is critical in the longterm health of humans. They are the rarely celebrated government agency we would all be worse off without.

*To this point, the Republican-led congress has declined to pass the most aggressive proposed cuts, but have assented to decreases in science budgets for NIH, NSF, and NOAA, while maintaining the status quo for NASA. (Nature.com)

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