Is coffee really bad for you?

4 min read

"Coffee is bad for your stomach." "Too much is bad for you." And yet you also hear that "coffee drinkers live longer."

Which is true? Putting together a summary of the research with official guidance, the answer is "it depends on how much, and when."

Pooling the research, risk was lowest around 3–4 cups

There's a study (an umbrella review) that gathered and organized more than 200 meta-analyses on coffee and health [1]. It looked at how the amount of coffee people drink relates to 67 health outcomes.

Its conclusion: at usual amounts, coffee is generally safe and more likely to benefit health than harm it. Across various outcomes, including death and cardiovascular disease, risk was lowest at around 3–4 cups a day.

But this is "association," not "effect"

Most of the studies in this summary are observational studies that followed coffee drinkers and non-drinkers. People who drink coffee may have been healthier to begin with, or have different lifestyles.

So we can't say "drink coffee and you'll live longer." What we can say goes only as far as: "among people drinking usual amounts of coffee, results showing higher health risks were rarely seen."

Some people should be careful

The same study also found results that call for caution. High intake during pregnancy was associated with low birth weight, preterm birth, and miscarriage. And among women, an association with fracture risk was seen (not among men) [1].

If you're pregnant or breastfeeding, take medication for a chronic condition, or tend to get palpitations or insomnia from caffeine, it's better to cut back or talk to a doctor.

The caffeine guideline: up to 400 mg a day

The European Food Safety Authority (EFSA) says that for healthy adults, caffeine up to 400 mg a day and up to 200 mg at a time raises no safety concerns. During pregnancy and breastfeeding, the guide is up to 200 mg a day [2]. Japan has no official caffeine intake standard, but Japan's Food Safety Commission also cites overseas guidance like this [3].

Drip coffee contains about 60 mg of caffeine per 100 mL [3]. Taking a cup as 150 mL, that's about 90 mg.

Energy drinks, green tea, black tea, and chocolate contain caffeine too. Think in terms of the total, not just coffee.

Easy to overlook: the effect on sleep

In an experiment with 12 healthy people who took 400 mg of caffeine right before bed, 3 hours before, or 6 hours before, even taking it 6 hours before bed shortened measured sleep by more than an hour. And the participants themselves barely noticed that their sleep had been disrupted [4].

But this was a small experiment with 12 people, and 400 mg is a large amount, about four cups of coffee. We can't say the same happens with one cup. Still, if you don't sleep well at night, it seems worth cutting back on late-afternoon coffee.

Summary

• Pooling the research, usual amounts of coffee are considered generally safe. Risk was lowest around 3–4 cups a day (observational studies)
• For healthy adults, the guide is up to 400 mg of caffeine a day and 200 mg at a time; up to 200 mg a day during pregnancy and breastfeeding
• Go easy if you're pregnant, a woman worried about fractures, or sensitive to caffeine
• If your sleep feels shallow, rethink coffee late in the afternoon

Coffee isn't something to write off as bad for you, nor something to drink for your health. I think it's something to enjoy, with set amounts and times.

How to choose beans, filters, and decaf is in a separate article, how to choose and brew coffee.