Drinking coffee is more likely to benefit health than to harm it for a range of health outcomes, researchers from the British Medical Journal (BMJ) found. Coffee drinking is also associated with lower risk of some cancers, diabetes, liver disease, and dementia, according to the new research.

To evaluate the existing evidence for associations between coffee consumption and multiple health outcomes, the researchers brought evidence from over 200 studies and found that 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.

Coffee is a very popular drink and is highly consumed worldwide, and it could have positive health benefits, especially in chronic liver disease. Beneficial or harmful associations of drinking coffee seem to vary between health outcomes of interest. For the authors of the study, understanding associations of coffee and health is important, especially in relation to exploring harmful associations, before interventional research is conducted.

The researchers, led by Robin Poole, specialty registrar in public health at the University of Southampton, have carried out an umbrella review of the evidence across meta-analyses of 201 observational and interventional studies that had aggregated data from observational research and 17 studies that had aggregated data from clinical trials across all countries and all settings. That umbrella review enabled them to better understand the effects of coffee consumption on health. It also reviewed previous meta-analyses and provided a high-level summary of research on a particular topic, according to the study.

What this study adds is that coffee drinking seems safe within usual patterns of consumption, except during pregnancy and in women at increased risk of fracture. It also says that existing evidence is observational and of lower quality, and that randomised controlled trials are needed. A future randomised controlled trial in which the intervention is increasing coffee consumption would be unlikely to result in significant harm to participants, according to the research.