Black coffee, longer life: The science behind your morning perk

The study, published online in The Journal of Nutrition, found that consumption of 1-2 cups of caffeinated coffee per day was linked to a lower risk of death from all causes and death from cardiovascular disease. Black coffee and coffee with low levels of added sugar and saturated fat were associated with a 14% lower risk of all-cause mortality as compared to no coffee consumption. The same link was not observed for coffee with high amounts of added sugar and saturated fat.

"Coffee is among the most-consumed beverages in the world, and with nearly half of American adults reporting drinking at least one cup per day, it's important for us to know what it might mean for health," said Fang Fang Zhang, senior author of the study and the Neely Family Professor at the Friedman School. "The health benefits of coffee might be attributable to its bioactive compounds, but our results suggest that the addition of sugar and saturated fat may reduce the mortality benefits."

The study analyzed data from nine consecutive cycles of the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2018, linked to National Death Index Mortality Data. The study included a nationally representative sample of 46,000 adults aged 20 years and older who completed valid first-day 24-hour dietary recalls. Coffee consumption was categorized by type (caffeinated or decaffeinated), sugar, and saturated fat content. Mortality outcomes included all-cause, cancer, and cardiovascular disease. Low added sugar (from granulated sugar, honey, and syrup) was defined as under 5% of the Daily Value, which is 2.5 grams per 8-ounce cup or approximately half a teaspoon of sugar. Low saturated fat (from milk, cream, and half-and-half) was defined as 5% of the Daily Value, or 1 gram per 8-ounce cup or the equivalent of 5 tablespoons of 2% milk, 1 tablespoon of light cream, or 1 tablespoon of half-and-half.

In the study, consumption of at least one cup per day was associated with a 16% lower risk of all-cause mortality. At 2-3 cups per day, the link rose to 17%. Consumption beyond three cups per day was not associated with additional reductions, and the link between coffee and a lower risk of death by cardiovascular disease weakened when coffee consumption was more than three cups per day. No significant associations were seen between coffee consumption and cancer mortality.

"Few studies have examined how coffee additives could impact the link between coffee consumption and mortality risk, and our study is among the first to quantify how much sweetener and saturated fat are being added," said first author Bingjie Zhou, a recent Ph.D. graduate from the nutrition epidemiology and data science program at the Friedman School. "Our results align with the Dietary Guidelines for Americans which recommend limiting added sugar and saturated fat."

Limitations of the study include the fact that self-reported recall data is subject to measurement error due to day-to-day variations in food intake. The lack of significant associations between decaffeinated coffee and all-cause mortality could be due to the low consumption among the population studied.

Additional authors are Yongyi Pan and Lu Wang, both of the Friedman School, and Mengyuan Ruan, a graduate of the Friedman School.

The study was supported by the National Institutes of Health's National Institute on Minority Health and Health Disparities under award number R01MD011501. Complete information on methodology is available in the published paper. The content is the sole responsibility of the authors and does not necessarily represent the official views the National Institutes of Health.