Coffee: what the research shows about 3 to 4 cups a day

Coffee is one of the most thoroughly studied foods there is. A 2017 review in the BMJ gathered every meta-analysis available: 201 analyses of observational studies covering 67 health outcomes, plus 17 analyses of intervention studies. The result: coffee was linked to benefit more often than to harm.¹

What the studies show

The link was strongest at 3 to 4 cups a day, compared with people who drink no coffee:¹

Heavy coffee drinkers were also 18% less likely to develop cancer than light drinkers. The researchers also found lower risks for several specific cancers and for liver, metabolic and neurological conditions.¹

The relationship is not linear. More coffee does not always mean more benefit; the largest risk reduction came at 3 to 4 cups.¹

Why this is not a free pass

Almost all of these figures come from observational studies. Smoking shows how much other factors matter: most harmful associations disappeared once studies properly accounted for smoking. The authors therefore call for randomized trials to establish whether coffee itself is the cause.¹

Two exceptions remained. In pregnancy, high coffee intake was linked to lower birth weight, more preterm births and more pregnancy loss. And women who drank a lot of coffee had more fractures; men did not.¹

How much caffeine is safe

In 2015, the European Food Safety Authority assessed which amounts are safe for healthy people:²

• Adults: up to 400 mg of caffeine a day, spread over the day, and up to 200 mg at once.
• Pregnant and breastfeeding women: up to 200 mg a day.
• Children and adolescents: up to 3 mg per kilogram of body weight a day.

By EFSA’s figures, a cup of filter coffee (200 ml) contains about 90 mg of caffeine and an espresso (60 ml) about 80 mg.⁵ So 400 mg is a little over 4 cups of filter coffee or 5 espressos. Caffeine from tea, cola, chocolate and energy drinks counts too.

Coffee and sleep

In a small study, 12 healthy sleepers took 400 mg of caffeine, by EFSA’s figures a little over 4 cups of filter coffee at once. They took it at bedtime, 3 hours before or 6 hours before. In all three cases they slept measurably worse than with a placebo; even 6 hours before, their sleep was cut by more than an hour. The researchers therefore advise avoiding substantial amounts of caffeine for at least 6 hours before bed.³ If you go to sleep at 10:30 pm, larger amounts of caffeine should come by 4:30 pm, and earlier is better.

Caffeine calculator

On a normal day

Filter coffeecup, 200 ml, 90 mg−

2

+

Espresso60 ml, 80 mg−

1

+

Black teacup, 220 ml, 50 mg−

0

+

Colacan, 355 ml, 40 mg−

0

+

Energy drinkcan, 250 ml, 80 mg−

0

+

Plain chocolate50 g, 25 mg−

0

+

Milk chocolate50 g, 10 mg−

0

+

For whom

AdultsPregnant or breastfeedingUnder 18

You go to bed at

Caffeine per day260 mgabout 3 cups of filter coffee

Limit: 400 mg65%

✓Below the 400 mg a day that EFSA considers safe for healthy adults.

• At most 200 mg at once, about 2 cups of filter coffee.
• Larger amounts no later than 16:30, 6 hours before bed. Even 100 mg close to bedtime can disturb sleep.

EFSA reference values per portion. The actual content varies widely with the bean and the brewing method.

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Filtered or unfiltered

A meta-analysis of 12 randomized trials with 1,017 participants found that drinking coffee for about 45 days raised total cholesterol by 8.1 mg/dl (about 0.21 mmol/l) and LDL cholesterol by 5.4 mg/dl (about 0.14 mmol/l) on average. The rise was larger with unfiltered coffee, and people with high blood lipids reacted more strongly.⁴ If you need to watch your cholesterol, filter coffee is the better choice.