People who increased the amount of coffee they drank each day by more than one cup over a four-year period had a 11% lower risk for type 2 diabetes than those who made no changes to their coffee consumption, according to a new study led by Harvard School of Public Health (HSPH) researchers.

In addition, the study found that those who decreased their coffee consumption by more than a cup per day increased their type 2 diabetes risk by 17%. “These findings further demonstrate that, for most people, coffee may have health benefits,” said Frank Hu, senior author and professor of nutrition and epidemiology at HSPH. “But coffee is only one of many factors that influence diabetes risk. More importantly, individuals should watch their weight and be physically active.”

The researchers analyzed data on caffeinated and decaffeinated coffee, and caffeinated tea consumption from 47,510 women in Nurses’ Health Study II (1991-2007), 27,759 men in the Health Professionals Follow-up Study (1986-2006), and 48,464 women in the Brigham and Women’s Hospital-based Nurses’ Health Study (1986-2006). Participants’ diets were evaluated every four years with a questionnaire, and those who self-reported type 2 diabetes filled out additional questionnaires.
A total of 7,269 cases of type 2 diabetes were documented.
A cup of coffee was defined as eight ounces, black, or with a small amount of milk and/or sugar.

Study author Rob van Dam (National University of Singapore and National University Health System, Singapore) received grant funding from Nestec Ltd for a randomized trial of the effects of coffee consumption on insulin sensitivity. Nestec Ltd is a broad food company that also sells coffee. This is grant funding specific for that project with a contractual agreement that ensures that the company cannot influence the design of the study or decision to publish the results. This funding does not in any way affect the current study. Other authors declare that there is no duality of interest associated with this manuscript.

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Harvard School of Public Health

“Changes in coffee intake and subsequent risk of type 2 diabetes: three large cohorts of US men and women,” Shilpa N. Bhupathiraju, An Pan, JoAnn E. Manson, Walter C. Willett, Rob M. van Dam, Frank B. Hu, Diabetologia, online April 24, 2014, DOI 10.1007/s00125-014-3235-7

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