A study that is currently in the news claims that people who drink two to three cups of coffee a day live longer than people who do not drink coffee. Should we all be drinking two to three cups? Not necessarily. Let’s take a look at where these numbers come from.
The Science of Why Coffee is Good for You
This recent study is based in the UK Biobank, where the average age is 58, just over half of the participants are women, and about 95% are white. On average, the researchers were able to follow participants for 12 years after they answered a question about how much coffee they drink.
When looking at all-cause mortality, people who drank two to three cups of coffee a day had the lowest risk, regardless of whether they drank ground, instant, or decaf. For cardiovascular disease, those who drank one cup a day had the lowest risk, but for arrhythmia (irregular heartbeat), the sweet spot seemed to be four to five cups. In the arrhythmia results, decaf coffee was not associated with a reduction in risk.
However, the study has many limitations if you're trying to use it to determine how much coffee you should drink. This group of middle-aged Brits may not be representative of the rest of the world; and it's not as if people randomly decide how much coffee to drink. Income, social class, and perceived health risks can all contribute to that choice, to name a few (Britons also tend to drink a lot of instant coffee and espresso, it turns out). The researchers also took people's self-reported data at face value and assumed they drank the same amount of coffee over time, rather than continually reassessing.
