Moderate coffee drinking is unlikely to cause harm and may even have health benefits.
A University of Southampton, UK review of more than 200 studies found three to four cups of coffee a day is of most benefit and is associated with a lower risk of heart disease, some cancers, diabetes, liver disease and dementia.
The exceptions were in pregnant women and women at risk of bone fractures, where less coffee was better. Low or no coffee consumption in pregnancy is associated with higher birth weight and lower risk of preterm births or pregnancy loss.
More investigation is needed, the research paper says, to establish whether the observed relationships with coffee are causal.
BMJ, December 2017