(RxWiki News) Many people drink caffeinated drinks like coffee or tea on a daily basis. It's possible that even small changes in coffee consumption could affect their health in a major way.
A recent study found that increasing coffee consumption over a four-year period was associated with a decreased risk of type 2 diabetes in the following four years, and decreasing coffee consumption over a four-year period was associated with an increased risk of type 2 diabetes in the following four-years.
"Discuss your daily coffee consumption with a doctor."
The lead author of this study was Shilpa N. Bhupathiraju, research fellow from the Department of Nutrition at the Harvard School of Public Health.
The study included participants from three previous studies. There were a total of 48,464 women from the Nurses' Health Study from 1986 to 2006, 47,510 women from the Nurses' Health Study II from 1991 to 2007 and 27,759 men from the Health Professionals Follow-up Study from 1986 to 2006.
The participants were from all 50 states, and were between 30 and 75 years old at enrollment in each of the studies. None of them were pregnant or had a history of diabetes, heart disease or cancer at four years after the start of each study.
The researchers recorded data on age, weight, smoking status, physical activity, menopausal status and hormone therapy use, birth control use, personal history of chronic diseases and type 2 diabetes status every two years.
Type 2 diabetes is a chronic condition in which the body becomes resistant to the insulin it produces, which causes high blood sugar.
Diet and consumption of coffee and tea were assessed every four years. A cup of coffee was defined as eight ounces of black coffee or eight ounces of coffee with a small amount of milk and/or sugar.
The findings showed that a total of 7,269 participants developed type 2 diabetes after 1,663,319 person-years (number of participants multiplied by number of years in study) of follow-up.
Over a four-year period, the average increase of coffee consumption was 1.69 cups per day, and the average decrease was 2.00 cups per day.
The researchers found that people who increased their coffee consumption by more than one cup per day over a four-year period were 11 percent less likely to develop type 2 diabetes in the following four-year period compared to people who did not change their average coffee consumption.
Compared to the participants who did not change their coffee consumption, the participants who decreased their coffee consumption by more than one cup per day had a 17 percent increased risk of developing type 2 diabetes during the following four-year period.
The findings revealed that these increases and decreases in type 2 diabetes risk were only associated with caffeinated coffee, and were independent of the participants' initial coffee consumption and four-year changes in other lifestyle and dietary factors.
Changes in tea consumption were not associated with increased or decreased risk of type 2 diabetes.
"Our findings confirm those of previous studies that showed that higher coffee consumption was associated with lower type 2 diabetes risk," Bhupathiraju said in a press statement. "Most importantly, they provide new evidence that changes in coffee consumption habit can affect type 2 diabetes risk in a relatively short period of time."
However, Dr. Frank Hu, co-author of this study and professor of nutrition and epidemiology at the Harvard School of Public Health, pointed out that "coffee is only one of many factors that influence diabetes risk." He added, "More importantly, individuals should watch their weight and be physically active."
These authors mentioned a few limitations of their study. First, only a small proportion of the participants drank decaffeinated coffee or tea, and the researchers did not differentiate between what types of tea the participants drank. Second, these findings may not be generalizable to everyone because the study groups consisted only of health professionals of European ancestry.
In addition, dietary information was self-reported, and the researchers did not know when the participants changed their coffee or tea consumption because it was only assessed every four years.
This study was published on April 24 in Diabetologia.
The National Institutes of Health provided funding.
