High Coffee/Decaf/Tea Intake Linked to Lower Diabetes Risk

Laurie Barclay, MD

December 14, 2009

December 14, 2009 — High intakes of coffee, decaffeinated coffee, and tea are associated with a reduced risk for type 2 diabetes, according to the results of a meta-analysis reported in the December 14/28 issue of the Archives of Internal Medicine.

"Coffee consumption has been reported to be inversely associated with risk of type 2 diabetes mellitus," write Rachel Huxley, DPhil, of the George Institute for International Health, University of Sydney in Sydney, Australia, and colleagues. "Similar associations have also been reported for decaffeinated coffee and tea. We report herein the findings of meta-analyses for the association between coffee, decaffeinated coffee, and tea consumption with risk of diabetes."

Using a combined text word and MeSH (Medical Subject Headings) search strategy, the investigators identified relevant studies through search engines. Inclusion criteria were prospective studies published between 1966 and July 2009 and reporting an estimate of the association between coffee, decaffeinated coffee, or tea with incident diabetes.

There were 18 studies, enrolling a total of 457,922 participants, reporting on the association between coffee consumption and diabetes. Of these, 6 (N = 225,516) also reported estimates of the association between decaffeinated coffee with diabetes, and 7 studies (N = 286,701) also reported estimates of the association between tea and diabetes.

After adjustment for potential confounders, there was an inverse log-linear relationship between coffee intake and the subsequent risk for diabetes, such that every additional cup of coffee consumed in 1 day was associated with a 7% decrease in the excess risk for diabetes (relative risk, 0.93; 95% confidence interval, 0.91 - 0.95).

"Owing to the presence of small-study bias, our results may represent an overestimate of the true magnitude of the association," the study authors write. "Similar significant and inverse associations were observed with decaffeinated coffee and tea and risk of incident diabetes."

Limitations of this study include observational design of included studies; possible confounding; and reliance on published data, precluding more detailed analysis. In addition, only 20% of the cohorts were from nonwhite populations, which somewhat limits the generalizability of the study findings to largely Western populations.

"If such beneficial effects were observed in interventional trials to be real, the implications for the millions of individuals who have diabetes mellitus, or who are at future risk of developing it, would be substantial," the study authors conclude. "For example, the identification of the active components of these beverages would open up new therapeutic pathways for the primary prevention of diabetes mellitus. It could also be envisaged that we will advise our patients most at risk for diabetes mellitus to increase their consumption of tea and coffee in addition to increasing their levels of physical activity and weight loss."

The study authors have disclosed no relevant financial relationships. Some of the study authors are supported by the National Heart Foundation of Australia, the National Health and Medical Research Council of Australia, the UK Wellcome Trust, and/or Institut Servier, France, and Assistance Publique-Hopitaux de Paris.

Arch Intern Med. 2009;169:2053-2063.


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.