The Real Scoop on Caffeine

Coffee drinking, in all its various forms, is nearly ubiquitous throughout the world. Yet, confounding and conflicting evidence has resulted in much confusion regarding the most popular drug in the world–caffeine. So what does the best available evidence tell us?

To discover any associations between coffee consumption and health outcomes the authors conducted a meta-analyses of both observational and interventional studies using data from PubMed, Embase, CINAHL, and Cochrane Database of Systematic Reviews. Inclusion criteria were both observational and interventional studies designed to examine the relationship between coffee consumption and any health outcome among adults from any country or culture. Studies of genetic polymorphisms for coffee metabolism were not included in the analysis.

The authors identified 201 meta-analyses of observational research, 67 unique health outcomes, and 17 meta-analyses of interventional research with nine outcomes.

Ask the ExpertThe overarching finding from the analysis revealed that coffee consumption was associated with more benefit than harm, even when looking at a wide range of health issues and outcomes and adjusting for high versus low consumption and no consumption.
There is a non-linear association between consumption of 3 to 4 cups per day and a reduction of relative health risks including all cause (relative risk 0.83, 95% confidence interval 0.83 to 0.88) and cardiovascular mortality (0.81, 0.72 to 0.90), plus the incidence of cardiovascular disease (0.85, 0.80 to 0.90).

Higher versus lower coffee consumption is associated with an 18% decrease risk for incident cancer (0.82, 0.74 to 0.89) and with a lower risk of several specific cancers as well as protection against neurological, metabolic, and liver conditions. The harmful associations were largely nullified by adjusting for smoking, and pregnancy—which was associated with lower birth weight, (odds ratio 1.31, 95% confidence interval 1.03 to 1.67), preterm birth in the first (1.22, 1.00 to 1.49) and second (1.12, 1.02 to 1.22) trimester, and pregnancy loss (1.46, 1.06 to 1.99).

This analysis suggests that coffee consumption of 3-4 cups per day is generally safe and associated with risk reduction for various detrimental health outcomes. Certainly controlled clinical trials are needed to better understand whether or not the associations identified in the meta-analysis are causal.

Why Does This Matter?

For those who like their coffee, in moderation, but have worried about effects on their health, this is good news. However, our individual health risks vary dramatically via our unique genetics and environmental conditions. Lastly, the use of caffeine in the treatment settings has been somewhat unclear, with the predominant thinking that using any mood altering substance is not a good idea for those with SUD. These data may be of benefit to those who make policy in such centers. But the trend that coffee offers numerous protection factors and is an excellent antioxidant must also be considered and discussed with one’s personal physician.

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 Nov 22;359:j5024. doi: 10.1136/bmj.j5024.