Researchers from the Harvard T.H. Chan School of Public Health said drinkers of both fully caffeinated and decaffeinated coffee saw a lower risk of cardiovascular and neurological diseases, type-2 diabetes and even suicide.
Lead author Ming Ding, a doctoral student at Harvard’s Department of Nutrition, said the reason for this may be the bioactive compounds in coffee. These help to reduce both insulin resistance and systematic inflammation.
What researchers looked at
Researchers looked at association of risk and subsequent mortality among tens of thousands of people throughout the Nurses’ Health Study and Health Professionals Follow-up Study. This was measured with consumption of total, caffeinated and decaffeinated coffee.
“Consumption of total, caffeinated, and decaffeinated coffee were non-linearly associated with mortality,” according to the Harvard study. “Compared to non-drinkers, coffee consumption one to five cups [per day] was associated with lower risk of mortality, while coffee consumption more than five cups/d was not associated with risk of mortality.”
Researchers found “significant inverse associations” between coffee consumption and death due to cardiovascular disease, neurological disease and suicide. There were no links found between coffee consumption and cancer mortality.
A non-linear association was observed between coffee and mortality in the entire population of the study, but researcher said this was likely due to smoking, as this association disappeared when tobacco smokers were factored out.
Strengths and limitations
With a large sample size, long-follow up time in the studies and large number of deaths in the data to help researchers provide the non-linear association, researchers said they had a good number of strengths within this study. However, they also noted that there were limitations to be considered.
“First, given the observational nature of the study design, we could not directly establish a cause-effect relationship between coffee and mortality,” the researchers said.
Also, the assessment was based on questionnaires, meaning measurement errors were inevitably made. However, the Harvard researchers said validation studies “have demonstrated high validity” when compared with multiple week diet records. There was also high reproducibility due to comparing consecutive food questionnaires by those who participated in the studies.
“Regular consumption of coffee was inversely associated with risk of total mortality and mortality due to CVD, and neurological disease,” the study concluded. “Similar associations of caffeinated and decaffeinated coffee consumption with risk of total and cause-specific mortality were found.
"Results from this and previous studies indicate that coffee consumption can be incorporated into a healthy lifestyle.”
This study appeared online in Circulation this month. Read it in full here.
Association of Coffee Consumption with Total and Cause-Specific Mortality in Three Large Prospective Cohorts
Authors: M. Ding; A. Satija; S. Bhupathiraju; Y. Hu; Q. Sun; J. Han; E. Lopez-Garcia; W. Willett; R. van Dam; F. Hu