Americans love coffee, and each sip of it may be lowering risk of early death for the 54 percent of adults who drink it every day. In a new study, researchers from the Harvard School of Public Health studied the benefits of both caffeinated and decaffeinated coffee, and found both conferred a lower risk of dying from the leading causes of death in the United States.

"This study provides further evidence that moderate consumption of coffee may confer health benefits in terms of reducing premature death due to several diseases," the study’s senior author Frank Hu, a nutrition and epidemiology professor at Harvard, said in a press release. "These data support the 2015 Dietary Guidelines Advisory Report that concluded that 'moderate coffee consumption can be incorporated into a healthy dietary pattern.'"

For the study, published in the journal Circulation, researchers analyzed data from three 30-year-old ongoing studies. The studies comprised of 208,501 participants in total, who completed a follow-up questionnaire about their diet every four years. The researchers also tracked coffee consumption among the participants over the years and found a pattern emerge that was directly related to how much coffee they drank on an average day.

Those who drank about 3 to 5 cups of coffee a day were far less likely to die from life-shortening illnesses like heart disease, type 2 diabetes; neurological diseases like Parkinson’s disease; and even suicide. In their study, researchers also accounted for environmental factors that influence death, such as smoking, body mass index, physical activity levels, alcohol consumption, and other dietary factors. Ultimately, coffee proved to be linked to the lower death rate.

"Bioactive compounds in coffee reduce insulin resistance and systemic inflammation," said the study’s co-author Ming Ding, a doctoral student at Harvard’s Department of Nutrition, in the press release. "That could explain some of our findings. However, more studies are needed to investigate the biological mechanisms producing these effects."

Previously, researchers have found drinking 4 to 5 cups of coffee a day could cut a person’s risk of Parkinson’s disease nearly in half, when compared to those who drank little to no coffee. In a more recent study on coffee’s benefits, the same 3 to 5 cups a day reduced risk of dying from heart disease by 21 percent.

It was only a decade ago that Harvard researchers first discovered too much coffee did not cause high blood pressure. Several years later, they examined 36 studies encompassing more than one million participants and found heavy coffee consumption actually protects the heart and lowers the risk of heart disease.

Then last year, Harvard researchers made a number of promising discoveries after analyzing the effects of coffee consumption on the human genome. The team uncovered six genes. Two were related to how fast or slow coffee is metabolized within the body; another two related to coffee’s psychoactive effects within the brain; and two genes whose roles still remain unclear. The discoveries provided new insight into why caffeine affects people differently, and how these effects influence coffee consumption.

Down to the DNA level, the effects of coffee continue to be discovered. However, because these effects are consistent among both caffeinated and decaf coffee drinkers, it’s unclear exactly how the coffee bean works within the body. While some effects may be due to caffeine’s influence in the body, other effects may be linked to other properties within the bean.

“Coffee is a complex beverage,” Hu said. “It’s very difficult to pinpoint which component of coffee is responsible for the benefit.”

Source: Hu F, Ding M, Satija A, et al. Association of Coffee Consumption with Total and Cause-specific Mortality in Three large Prospective Cohorts. Circulation. 2015.