In an umbrella review on meta-analyses evaluating the association between coffee consumption and multiple health outcomes, coffee was found to be generally safe to drink, with more benefit to health than harm, according to a recent study published in the British Medical Journal.1
Researchers analyzed 201 meta-analyses of observational research with 67 unique health outcomes and 17 meta-analyses of interventional research with 9 unique outcomes. Coffee consumption was measured in various exposures, including high vs low consumption, any vs none, and 1 extra cup a day. Meta-analysis quality was assessed via AMSTAR, a measurement tool to assess systematic reviews, and GRADE (Grading of Recommendations, Assessment, Development, and Evaluation).
Coffee consumption was shown to benefit multiple health outcomes. The 10 most beneficial associations were with type 2 diabetes, oral cancer, cirrhosis, renal stones, Parkinson disease, leukemia, mortality after myocardial infarction, gout, liver cancer, and chronic liver disease.
The highest exposure of coffee consumption (7 cups a day) was linked to a 10% lower risk for all-cause mortality (relative risk, 0.90; 95% CI, 0.85-0.96). However, the largest relative risk reduction was linked to 3 cups a day (0.83; 95% CI, 0.83-0.88).
Coffee consumption was not significantly associated with harmful health outcomes. However, the highest relative risk estimates were in acute childhood leukemia, lung cancer, pregnancy loss, rheumatoid arthritis, low birth weight, lymphoma, laryngeal cancer, first trimester preterm birth, third trimester preterm birth, and oral cleft malformation.
Researchers observed inconsistencies regarding harmful associations of coffee consumption on health outcomes related to pregnancy. Compared with low coffee consumption, high consumption was linked with a higher risk for pregnancy loss (odds ratio, 1.46; 95% CI, 1.06-1.99) and low birth weight (odds ratio, 1.31; 95% CI, 1.03-1.67).
“There is no consistent evidence of harmful associations between coffee consumption and health outcomes, except for those related to pregnancy and for risk of fracture in women,” concluded the researchers.
The review may be limited by potential bias introduced from reverse causality and by inconsistencies in the way coffee consumption was measured.
In response to the study, Eliseo Guallar, MD, from the Departments of Epidemiology and Medicine at Johns Hopkins Bloomberg School of Public Health, wrote, “The evidence is so robust and consistent across studies and health outcomes, however, that we can be reassured that drinking coffee is generally safe, although some caveats apply.”2
- Poole R, Kennedy OJ, Roderick P, Fallowfield JA, Hayes PC, Parkes J. Coffee consumption and health: umbrella review of meta-analyses of multiple health outcomes. BMJ. 2017;359:j5024.
- Guallar E. Coffee gets a clean bill of health. BMJ. 2017;359:j5356.