Drinking a moderate amount — 1.5 to 3.5 cups per day — of unsweetened or sugar-sweetened coffee was associated with a lower risk for mortality, according to findings published in Annals of Internal Medicine.

An association between artificially sweetened coffee and mortality risk was less conclusive, researchers reported.

“Of note, many of the observed associations (including our findings) between high coffee consumption and morbidity and mortality are present with caffeinated as well as decaffeinated coffee, and thus it seems unlikely that caffeine alone can explain all potential health effects of coffee,” Dan Liu, MD, of the department of epidemiology at Southern Medical University and the department of public health and preventive medicine at Jinan University in Guangzhou, China, and colleagues wrote.

In a prospective, population-based cohort study, Liu and colleagues evaluated 171,616 adults in the United Kingdom without prior CVD or cancer. Participants were enrolled in the U.K. Biobank and had a mean age of 55.6 years; 44.6% of participants were men and 95.7% were white. For the analysis, the participants completed WebQ, an online 24-hour dietary recall questionnaire in which they indicated how many drinks of coffee they had as well as any added sugar or artificial sweeteners they put in their coffee. Liu and colleagues categorized one drink as about 250 mL. They analyzed mortality and outcome data over 7 years of follow-up from 2009 to 2018.

Coffee intake and mortality

The average amount of sugar added to coffee was 1.1 teaspoons and the average amount of artificial sweetener added was about 2.1 teaspoons daily.

In total, 1,725 deaths from cancer and 628 deaths from CVD occurred during the study period, Liu and colleagues reported. Consumers of unsweetened coffee had a lower risk for all-cause mortality compared with nonconsumers:

• zero to 1.5 cups: HR = 0.79; 95% CI, 0.7-0;
• 1.5 to 2.5 cups: HR = 0.84; 95% CI, 0.74-0.95;
• 2.5 to 3.5 cups: HR = 0.71; 95% CI, 0.62-0.82;
• 3.5 to 4.5 cups: HR = 0.71; 95% CI, 0.6-0.84; and
• greater than 4.5 cups: HR = 0.77; 95% CI, 0.65-0.91.

Similarly, there was a lower all-cause mortality risk among consumers of sugar-sweetened coffee compared with nonconsumers:

• zero to 1.5 cups: HR = 0.91; 95% CI, 0.78-1.07;
• 1.5 to 2.5 cups: HR = 0.69; 95% CI, 0.57-0.84;
• 2.5 to 3.5 cups: HR = 0.72; 95% CI, 0.57-0.91; and
• 3.5 to 4.5 cups: HR = 0.79; 95% CI, 0.6-1.06.

However, adults who drank more than 4.5 cups of sugar-sweetened coffee had an increased risk for mortality (HR= 1.05; 95% CI, 0.82-1.36), according to the researchers.

The association between unsweetened coffee and mortality from cancer and CVD was largely consistent with that of all-cause mortality and statistically significant (P < .001). The associations with sugar-sweetened and artificially sweetened coffee were observed in some cases and only for cancer mortality, Liu and colleagues reported.

The results were consistent for consumers of instant and ground coffee.

“Coffee is a complex mixture, and several biological mechanisms have been examined to explain both the beneficial and the harmful effects of coffee intake on risk for death,” Liu and colleagues wrote. “It has been proposed that potential beneficial effects are seen mostly with moderate coffee intake, whereas harmful effects increase with high intake.”

‘Far from settled science’

In an editorial on the study, Christina C. Wee, MD, MPH, the associate program director for the internal medicine program at Beth Israel Deaconess Medical Center and the deputy editor of Annals of Internal Medicine, said “the benefits of coffee are far from settled science.”

Liu and colleagues fell short of addressing whether sweetened coffee is beneficial or harmful to health, according to Wee. Moreover, the average amount of sugar participants reported adding to their coffee does not approach the high amounts of sugar added to coffee purchased at popular coffee chains in the U.S. The study does indicate that small amounts of sugar may not be harmful and may benefit a person’s risk for mortality.

“Although we cannot definitively conclude that drinking coffee reduces mortality risk, the totality of the evidence does not suggest a need for most coffee drinkers — particularly those who drink it with no or modest amounts of sugar — to eliminate coffee,” Wee wrote.