Drinking coffee is “more likely to benefit health than to harm it” for a range of health outcomes, according to UK researchers.
They have calculated that three or four cups a day confers greatest benefit, except in pregnancy and for women at risk of fracture.
“The largest reduction in relative risk was associated with the consumption of three cups a day”
They analysed over 200 studies and concluded that drinking three to four cups of coffee a day was associated with a lower risk of death and getting heart disease, compared with drinking none.
Coffee drinking was also associated with lower risk of some cancers, diabetes, liver disease and dementia, found the researchers from the University of Southampton and University of Edinburgh.
However, they cautioned that drinking coffee during pregnancy could be associated with harms, and may also be linked to a very small increased risk of fracture in women.
With the exception of pregnancy and women at risk of fracture, the study authors said that “coffee drinking appears safe within usual patterns of consumption”.
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To better understand the effects of coffee consumption on health, they reviewed 201 studies that had aggregated data from observational research and 17 studies that had aggregated trial data.
Coffee drinking was consistently associated with a lower risk of death from all causes and heart disease, with the largest fall in relative risk of death at three cups a day, compared with no coffee.
Increasing consumption to above three cups a day was not associated with harm, but the beneficial effect was less pronounced, said the researchers in the British Medical Journal.
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, according to the research team led by Dr Robin Poole, specialist registrar in public health at Southampton University.
In addition, the noted that there seemed to be beneficial associations between coffee consumption and Parkinson’s disease, depression and Alzheimer’s disease.
“Moderate coffee consumption seems remarkably safe”
There was less evidence for the effects of drinking decaffeinated coffee, but it had similar benefits for a number of outcomes.
In the wake of their findings, the study authors called for robust randomised controlled trials to take place in order “to understand whether the key observed associations are causal”.
Commenting on the new study, Eliseo Guallar, from the Johns Hopkins Bloomberg School of Public Health in the US, cautioned that clinicians should not recommend drinking coffee to prevent disease.
Some people may be at higher risk of adverse effects and there was “substantial uncertainty” about the effects of higher levels of intake, he wrote in a linked editorial in the same journal.
However, even with these caveats and others, “moderate coffee consumption seems remarkably safe, and it can be incorporated as part of a healthy diet by most of the adult population”, he added.