Caffeine can briefly impair glucose control, raising a longer-term question about daily coffee habits and the development of diabetes.
Chronic coffee consumption and diabetogenic risk: data from the PAMELA study. Image Credit: kien thiet ke / Shutterstock
In a recent study published in the journal Nutrition, Metabolism and Cardiovascular Diseases, researchers investigated whether chronic coffee intake is associated with a diabetogenic risk.
Analyses from the Italian PAMELA study have shown that chronic coffee intake was not associated with changes in blood pressure (BP). Whether a similar pattern applies to glucose metabolism, especially in the context of type 2 diabetes (T2D), remains unknown. A large body of evidence suggests neutral or modestly protective associations of habitual coffee consumption with incident T2D. Experimental evidence also shows that caffeine can acutely decrease insulin sensitivity and impair glucose tolerance.
About the study
In the present study, researchers evaluated the associations between chronic coffee intake and the development of T2D or impaired fasting glucose (IFG), defined as an elevated fasting blood sugar level. They used data from the PAMELA study, which recruited adults aged 25 to under 75 years from Monza, Italy. Data on medical history, cardiometabolic risk factors, BP, heart rate, and anthropometric measures were collected at baseline. The estimated glomerular filtration rate (eGFR) served as a measure of kidney function.
Laboratory analyses were performed to measure plasma levels of glucose, triglycerides, total cholesterol, and high-density lipoprotein cholesterol (HDL-C). Chronic coffee consumption was assessed using a questionnaire, and respondents were grouped as non-consumers (no intake per day) or consumers (at least two to three cups per day). The study did not report results for lower levels of coffee intake. Tea, decaffeinated coffee, and other caffeinated beverages were not assessed.
All measures were repeated after 10 years of follow-up. IFG was defined as a fasting glucose level of at least 110 but less than 126 mg/dL; diabetes was defined as a fasting glucose level of at least 126 mg/dL or use of antidiabetic medication. The team compared new cases of T2D and IFG after accounting for baseline characteristics including age, sex, and serum glucose levels. They also matched participants with similar baseline characteristics to check whether the unequal group sizes affected the findings.
Findings
The study included 1,158 of the original 2,028 participants, with 1,059 coffee consumers and 99 non-consumers, who maintained their coffee-consumption status during follow-up. Consumers were more likely to be smokers and drinkers and showed higher body mass index (BMI) and weight than non-consumers. BP, heart rate, fasting glucose levels, and the proportions with IFG and T2D were comparable between groups at baseline.
The use of antidiabetic and antihypertensive medications was also comparable between non-consumers and consumers. After 10 years, both groups showed higher weight, BMI, systolic BP, triglyceride, and glucose levels, and lower total cholesterol, eGFR, and LDL-C levels. The proportions of smokers and drinkers remained virtually unchanged in both groups.
The proportions of participants with IFG and T2D, as well as those using antihypertensive medications, increased significantly in both groups. New cases of IFG and T2D did not differ significantly between the groups. The matched analysis indicated that the main results were unaffected by the sample-size imbalance, although the estimates were imprecise. The researchers also found no substantial difference when they examined coffee consumed with or without sugar.
Conclusions
In this cohort, participants consuming at least two to three cups of coffee per day did not have significantly different rates of new IFG or T2D from non-consumers over 10 years. The small non-consumer group and imprecise estimates mean the study cannot rule out a difference in risk.
The study’s limitations include its observational design, self-reported coffee intake, the exclusion of participants who did not complete both assessments, and a lack of information on caffeine content, coffee types, detailed amounts consumed, and changes in energy and nutrient intake during the follow-up period.
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