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Does CRAVE Improve Our Understanding of the Health Effects of Drinking Coffee?

In 2019 (on National Coffee Day!) the skeptical cardiologist revealed that he was a coffee snob and addict. Despite my love of coffee, as a scientist, I try to approach the health benefits or harms of coffee drinking from a neutral perspective.

A new study on coffee has stirred up the media, the Twitterverse, and possibly Mr. and Mrs. John Public. Is there anything to be learned from it?

My perspective in 2019 was that “although numerous studies have established that coffee consumption is safe (assuming you are not adding titanium dioxide to your cup), the belief that it is bad for you persists in the majority of patients that I see.

While it is possible to adulterate coffee into an unhealthy concoction (see my post on “How Starbucks Is Making Heart-Healthy Coffee Into a Stealth Dessert”) overall coffee is heart-healthy.

Has this new study or any new information since 2019 changed my conclusions?

The coffee and real-time atrial and ventricular ectopy trial: 48 hours on and 48 hours off coffee

The recently published Coffee and Real-time Atrial and Ventricular Ectopy (CRAVE) trial was designed to “assess the acute effects of coffee consumption on cardiac ectopy, physical activity, sleep, and glucose levels by using continuously recording, wearable sensors to assess healthy participants who were randomly assigned to alternate between consuming and avoiding caffeinated coffee.”

Participants were randomly assigned over a 2 weeks period to either drink coffee or abstain for 48 hours. They received text messages with their instructions.

Participants were tricked out to the max with gadgets to measure various things including continuous ECG (Zio patch), their geolocation (?near coffee shops), an accelerometer (Fitbit, for step counts and sleep duration) and a Dexcom G6 for continuous glucose monitoring.

Before reviewing any of the outcomes of this trial I see so many limitations as to render the results meaningless.

First, this is a highly select group of participants who were willing and eager to subject themselves to this protocol. One-third were Asian. Whether this applies to the general population or any individual is unclear Second, there is no direct measurement of coffee or caffeine consumption. The authors, aware of this limitation, employed four (weak) methods for assessing compliance. Third, the accuracy of Fitbit wrist devices for sleep duration is questionable. Fourth, participants were unblinded to coffee or no coffee. Fifth, people don’t consume coffee for two days on, then two days off. The experiment is not mimicking the real-world use of coffee. External validity is extremely limited.

What was found: More Steps and Less sleep

The author’s summary of their conclusions:

Among 100 healthy adults, “the consumption of caffeinated coffee did not result in more daily premature atrial contractions than the avoidance of caffeine. Our results further suggest that both assignments to daily coffee consumption and greater-than-normal coffee consumption were associated with more recorded daily steps taken, fewer minutes of sleep per night, and potentially more daily premature ventricular contrac- tions among persons who consumed more than one coffee drink per day.”

Given the limitations I have cited, all of these conclusions must be taken with a grain of Kosher salt.

But let’s assume that these volunteers were able to follow the text message instructions and not give in to the intense discomfort of caffeine withdrawal. It does not surprise me at all that upon resuming coffee consumption after 2 days of abstention that one would be more active. Personally, I am stimulated to walk/run/exercise when I get overcaffeinated. This would be exacerbated after withdrawal.

The variation in sleep duration could occur in a cycle of on caffeine and off caffeine, especially if the caffeine consumption was late in the day but again, this is not a real-world scenario.

Palpitations and Caffeine: Individual Level Findings

As to variations in PACs and PVCs, I don’t think this changes or informs the science in this area or my conclusions from 2019 due to the marked limitations of the study.

For more information on palpitations, PVCs, and the value of self-monitoring see my post describing in detail how one patient demonstrated very clearly the influence of caffeine on his heart rhythm.

Despite the absence of a demonstrable relationship between the frequency of extra-systoles and habitual caffeine consumption in the general population, I am convinced that PVCs in certain individuals (including myself) are triggered by higher levels of caffeine. Such a relationship is revealed by the type of self-experimentation performed by my reader.


In contrast to what the public believes, the scientific evidence very consistently suggests that drinking coffee is associated with living longer and having fewer heart attacks and strokes. Multiple publications in major cardiology journals in the last few years have confirmed this.
You can read the details here and here. The bottom line is that higher levels of coffee consumption (>1 cup per day in the US and >2 cups per day in Europe) are NOT associated with:

Higher levels of coffee consumption compared to no or lower levels ARE  associated with:

Idiosyncratically Yours,


N.B. All the studies showing the benefits of coffee consumption cited above are observational studies and come with the known limitations of these trials.

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