Coffee maker
A sweeping new review of decades of research suggests that moderate coffee drinking is doing more good than harm across a broad range of health outcomes.

Led by researchers at West Virginia University and Morgan State University in the United States, the review explored past academic studies and meta-analyses that combined account for more than 1 million participants from various world regions, including the U.S., Europe and Asia.

Published Aug. 5 in the MDPI journal Nutrients, the study offers a broadly sunny view of coffee's positive associations with better health, including a connection to longer life.

"Overall, the consensus is that moderate coffee intake is more beneficial than harmful across a wide range of health outcomes," the authors wrote, noting lower risk of major diseases such as cardiovascular diseases, diabetes, stroke, respiratory conditions, cognitive decline, and potentially several types of cancer, including liver and uterine cancers.

It should be noted that one of the study's two authors, Farin Kamangar, has served as a consultant for the National Coffee Association, a major trade group that historically has promoted health benefits of coffee in order to influence policy making and drive coffee consumption. Neither of the authors declared competing interests, and the work received no outside funding. They added that the NCA did not review the research prior to publication.

The magic consumption number appears to be about three to five cups of coffee per day, according to the paper. One major U.S. study tracking more than 400,000 adults found that people drinking two or more cups daily had a 10-15% lower risk of death from any cause. A massive 2019 analysis combining data from 3.8 million participants pinpointed the lowest death risk at roughly 3.5 cups per day.

Beyond general mortality, coffee drinkers have shown significantly lower rates of cardiovascular disease, type 2 diabetes, chronic respiratory disease, and certain neurodegenerative conditions.

In good news for decaf drinkers, the analysis also found that many of coffee's health-protective effects, particularly for type 2 diabetes and all-cause mortality, were comparable between caffeinated and decaffeinated coffee consumption.

"Where data was available, studies have assessed the association of caffeinated and decaffeinated coffee consumption with overall mortality. In almost all such analyses, both caffeinated and decaffeinated coffee were associated with reduced risk of mortality," the authors wrote. "However, individuals who drank decaffeinated in the year prior to the study might have been caffeinated coffee consumers previously, leading to a potential misclassification of the beneficial effects of caffeinated coffee for decaffeinated coffee."

As with any academic publication on coffee and human health, the analysis came with a slew of caveats.

Coffee additives, such as sugars or creamers, may serve to blunt some of the positive effects. Added sugar, in particular, may negate some neuroprotective or weight-related benefits, while studies of creamers have shown inconsistent results.

The paper also warns against high consumption among pregnant women, while high intakes of coffee may trigger anxiety or sleep disturbances in the general population.

The authors described the observational evidence on coffee and health, as collected over the past two decades as "relatively saturated."

"Therefore, it is unlikely that prospective cohort studies add substantial new information," they wrote. "If any new cohorts are developed, or if repeated data collection is considered, it may be useful to ask detailed questions about types of coffee drinking (e.g., caffeinated vs. decaffeinated), added cream and sugar, consumption of ground coffee vs. other types, etc."