A review of over 200 meta-analyses has determined that drinking three to four cups of coffee a day was linked with a lower mortality risk, lower cardiovascular mortality, as well as lower risk of developing cardiovascular disease. Additional benefits included a reduction in risk for type 2 diabetes, some forms of cancer (including prostate, endometrial, skin, and liver cancer), gallstones, and gout. The most significant benefit was seen for liver conditions, such as cirrhosis of the liver. The review also found coffee consumption seemed to benefit Parkinson's disease, depression, and Alzheimer's disease.
 
Some negative associations were found with those who drank coffee during pregnancy; coffee consumption was linked with low birth weight, preterm birth in the first and second trimester, and miscarriage. Additionally, researchers observed a connection between coffee drinking and risk of bone fracture for women (but not men).
 
The research team was led by Dr. Robin Poole, Specialist Registrar in Public Health at the University of Southampton, with collaborators from the University of Edinburgh. The team 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.
 
Upon concluding the review, researchers suggested coffee consumption “seems generally safe within usual levels of intake, with summary estimates indicating largest risk reduction for various health outcomes at three to four cups a day, and more likely to benefit health than harm.” They added that additional, robust, randomized controlled trials are needed to understand whether the observed associations are causal. Excluding pregnant women and those at risk of fracture, existing evidence suggests that coffee could be tested as an intervention without significant risk of causing harm.
 
The study, “Coffee consumption and health: umbrella review of meta-analyses of multiple health outcomes,” was published in BMJ.