A study released by the Harvard School of Public Health has confirmed a direct relationship between the amount of coffee a person drinks and a lowered risk for type 2 diabetes.

According to the study, those who increased their daily coffee consumption by more than one cup per day over a four-year period experienced an 11 percent lower risk of developing type 2 diabetes. Those who decreased their consumption by more than a cup per day, on the other hand, increased their risk by 17 percent.

Researchers also collected the same data on tea consumption, but no correlation was found between the drink and the disease.

“I was really happy to see that the changes themselves were associated with risk,” said School of Public Health postdoctoral fellow Shilpa Bhupathiraju, the study's lead author. “Increasing coffee decreases the risk for type 2 diabetes, while decreasing it raises it.”

The researchers analyzed data on caffeinated and decaffeinated coffee and tea consumption for over 120,000 participants from three separate studies over the course of more than 20 years.  Participants were evaluated every four years with a questionnaire, with those who had type 2 diabetes filling out additional forms. A total of 7,269 cases of type 2 diabetes were documented.

Unlike type 1 diabetes, type 2 diabetes can often be treated with lifestyle adjustments such as diet and exercise. Patients with type 2 diabetes are still capable of producing insulin, though this it is ineffective in controlling blood glucose levels. Occasionally, oral medication may be taken to control blood glucose levels, and insulin injections are sometimes prescribed.

“These findings further demonstrate that, for most people, coffee may have health benefits,” School of Public Health professor Frank B. Hu said in a press release. “But coffee is only one of many factors that influence diabetes risk. More importantly, individuals should watch their weight and be physically active.”

According to the American Diabetes Association, there are over 25 million people living with some form of diabetes in the United States, with type 2 diabetes as the most common form of the disease. Additionally, 79 million people are categorized as pre-diabetic or having a very high chance of contracting the disease sometime during their lives.

The study will appear online Thursday in Diabetologia, the journal of the European Association for the Study of Diabetes.

—Staff writer Conor J. Reilley can be reached at conor.reilley@thecrimson.com. Follow him on Twitter @c_reilley.