Coffee and your health: what the research says

The short answer

For most healthy adults, up to 400 mg of caffeine a day isn't linked to harmful effects. The FDA puts that at about two to three 12 oz cups of coffee. 1 2
Pregnant or breastfeeding? EFSA's level is 200 mg a day. Ask your doctor too. 2
In a big 2017 review, three to four cups a day went with a lower risk of several diseases. Those studies can't prove coffee is the cause. 4

How much caffeine is in your day?

Add the drinks you have on a normal day. Amounts are typical values from the Mayo Clinic; your cup can differ with the beans, the brew and the size. 3

The good

A 2017 BMJ umbrella review looked at more than 200 meta-analyses. Coffee came out more likely to benefit health than to harm it. 4

Linked with a longer life

Coffee drinkers had a lower risk of dying from any cause, with the biggest drop at three to four cups a day. 4

Lower risk of heart disease

The same review linked coffee with less cardiovascular disease and fewer deaths from it. 4

Kinder to the liver

Coffee went with a lower risk of liver conditions, including liver cancer. 4

Not shown to cause cancer

In 2016 the WHO's cancer agency, IARC, found no conclusive evidence that drinking coffee causes cancer, and lists it as "not classifiable". 6

These come from observational studies, so they show links, not causes. The BMJ authors say they can't recommend starting coffee for your health. 4

The not so good

None of this means coffee is bad for you. It means there are limits worth knowing.

It can cost you sleep

In a 2013 study, 400 mg of caffeine taken six hours before bed cut sleep by more than an hour, and people didn't notice. The AASM, which published it, says caffeine should generally be avoided after 5 p.m. 7

Unfiltered coffee and cholesterol

French press and Turkish coffee keep compounds called diterpenes, about 30 times more than filtered coffee. They can raise cholesterol. 5

Pregnancy needs a lower limit

High intake in pregnancy is linked with low birth weight, preterm birth and pregnancy loss. EFSA's level is 200 mg a day; check with your doctor. 4 2

Bones in women

The BMJ review found a higher fracture risk in women, though not in men. 4

Too much, too fast

Signs include jitters, anxiety, a fast heart rate and poor sleep. Toxic effects such as seizures can come from about 1,200 mg taken quickly: less than half a teaspoon of pure caffeine. 1

Very hot drinks

IARC classes drinks hotter than 65 °C as probably carcinogenic. Give your cup a minute. 6

The research is about coffee itself, not the sugar, syrups and pastries that often come with it. 4

Your filter matters

How you brew changes what ends up in the cup. Harvard Health suggests saving unfiltered coffee for rare occasions and keeping to fewer than five cups a day on average. 5

Filtered

Pour-over and drip

A filtered cup has about a thirtieth of the diterpenes of an unfiltered one. 5

Unfiltered

French press and Turkish

About 30 times more diterpenes than filtered coffee. 5

Who should be careful

Pregnant, trying or breastfeeding: the FDA says to ask your provider whether to limit caffeine; EFSA's level is 200 mg a day. 1 2
Children and teens: EFSA suggests 3 mg per kg of body weight a day as a safe level. 2
People who feel caffeine strongly: how sensitive people are, and how fast they clear caffeine, varies widely. If you cut back, go gradually: withdrawal isn't dangerous, but it can be unpleasant. 1
Women at risk of fractures or with osteoporosis: the BMJ authors suggest keeping coffee to a minimum. 4

Myth or fact?

Open a card to check.

"Decaf has no caffeine."

Myth. US rules require at least 97% of the caffeine to be removed, so a little is left. 8

"A shot of espresso has more caffeine than a mug of coffee."

Myth. A 1 oz shot has about 63 mg; an 8 oz cup of brewed coffee about 96 mg. Espresso is stronger per sip, not per serving. 3

"Coffee is on the list of things that cause cancer."

Myth. IARC's 2016 review found no conclusive evidence and lists coffee as "not classifiable". Drinks hotter than 65 °C are a separate warning. 6

"Up to 400 mg a day is fine for most healthy adults."

Fact. That's the level the FDA and EFSA use. Pregnancy has a lower one: 200 mg a day. 1 2

Sources

This guide is general information, not medical advice. If you have a health condition, take medication or are pregnant, talk to your doctor about caffeine.