Three coffees a day may have health benefits
Drinking three to four cups of coffee a day may lower the risk of death and developing heart disease as compared to non-drinkers, researchers claim in a review of over 200 studies.
Coffee drinking is also associated with lower risk of some cancers, diabetes, liver disease and dementia, researchers said.
The review published in The BMJ today journal found that coffee is "more likely to benefit health than harm it."
"Drinking three to four cups of coffee a day is associated with a lower risk of death and getting heart disease compared with drinking no coffee," researchers said.
However, they said that drinking coffee in pregnancy may be associated with harms, and may be linked to a very small increased risk of fracture in women.
The included studies used mainly observational data, providing lower quality evidence, so no firm conclusions can be drawn about cause and effect, but their findings back up other recent reviews and studies of coffee intake.
They said that excluding pregnancy and women at risk of fracture, "coffee drinking appears safe within usual patterns of consumption," suggesting that coffee could be safely tested in randomised trials.
To better understand the effects of coffee consumption on health, a team led by Robin Poole, from the University of Southampton in the UK, carried out an umbrella review of 201 studies that had aggregated data from observational research and 17 studies that had aggregated data from clinical trials across all countries and all settings.
Drinking coffee was consistently associated with a lower risk of death from all causes and from heart disease, with the largest reduction in relative risk of death at three cups a day, compared with non-coffee drinkers, researchers said.
Increasing consumption to above three cups a day was not associated with harm, but the beneficial effect was less pronounced, they said.
Coffee was also associated with a lower risk of several cancers, including prostate, endometrial, skin and liver cancer, as well as type 2 diabetes, gallstones and gout.
The greatest benefit was seen for liver conditions, such as cirrhosis of the liver.
There seem to be beneficial associations between coffee consumption and Parkinson's disease, depression and Alzheimer's disease, researchers said.
There was less evidence for the effects of drinking decaffeinated coffee but it had similar benefits for a number of outcomes, they said.
The researchers concluded that coffee drinking "seems safe within usual patterns of consumption, except during pregnancy and in women at increased risk of fracture."
They call for robust randomised controlled trials "to understand whether the key observed associations are causal.