Benefits of coffee now apparent in non-white and European populations
by Larry Husten, CardioBrief July 10, 2017
Two large new observational studies appearing Monday in Annals of Internal Medicine strengthened the association between higher coffee consumption and longer life. In the wake of earlier studies pointing to the potential benefits of coffee, the two new papers extend those benefits to new populations, including 10 European countries and non-white people in the U.S.
Because the studies are observational they were unable to determine whether coffee itself is beneficial, but the studies do offer a measure of reassurance for coffee lovers.
“Drink some coffee!” said Salim Yusuf of McMaster University in Hamilton, Ontario, when asked what he would advise a physician to tell patients who ask about coffee. Yusuf said the studies were “intriguing” but that it is necessary to “explore confounders” before reaching any conclusion.
In the first paper, researchers from the International Agency for Research on Cancer and Imperial College London analyzed data from 520,000 people in 10 countries participating in EPIC (European Prospective Investigation into Cancer and Nutrition), a large prospective cohort study. They found that, with mean 16.4 years of follow-up, people who drank coffee had a lower risk of death, with the greatest benefit occurring in people who drank three or more cups of coffee per day. The reduced risk of death was most evident in a reduction of deaths from digestive and circulatory diseases. The results were broadly consistent across countries, men and women, and other major subgroups.
In the second paper, U.S.-based researchers analyzed data from more than 185,000 African Americans, Japanese Americans, Native Hawaiians, Latinos, and whites participating in the MEC (Multiethnic Cohort) study, also with mean follow-up of about 16 years. They, too, reported an inverse relationship between coffee consumption and all-cause mortality. There were no differences among the different ethnic groups. (The result in Native Hawaiians did not reach statistical significance, probably because of the small number of Native Hawaiians enrolled in the study, according to the authors.) There were statistically significant reductions in deaths due to heart disease, cancer, chronic lower respiratory disease, stroke, diabetes, and kidney disease.
In both studies smoking played a large confounding role, since smokers are more likely to drink coffee. But the researchers reported that the association was consistent for never smokers, former smokers, and current smokers.
In an accompanying editorial, Eliseo Guallar and colleagues at Johns Hopkins University wrote that “a protective effect of coffee is biologically plausible.” However, they warned that the studies do not prove that coffee reduces mortality, since the relationship may be “just a reflection of uncontrolled confounding.”
Further, the association of coffee and mortality “was modest,” Guallar and colleagues cautioned. They said it would be “premature” to recommend coffee for its beneficial effects but “it is increasingly evident that moderate coffee intake up to 3 to 5 cups per day or caffeine intake up to 400 mg/d is not associated with adverse health effects in adults and can be incorporated into a healthy diet.”