This meta-analysis by Huxley et al. was performed to assess the association between coffee, decaffeinated coffee and tea consumption and the risk of type 2 diabetes mellitus (DM). This meta-analysis included a total sample of 500 000 individuals with over 21 000 cases of new-onset DM. The study confirmed an inverse association between coffee consumption and subsequent risk of DM with evidence of a dose-response relationship. For instance, every additional cup of coffee consumed daily was associated with 5% to 10% lower risk of incident DM after controlling for potential confounders. Moreover, the same relationship was observed regarding tea and decaffeinated coffee consumption. The fact that these relations are independent of a number of confounding variables suggests the possibility of direct biological effects. The authors raised the possibility that the protective effect of coffee and tea could be not only related to caffeine but also to a wide range of chemical constituents present in these beverages, such as magnesium, lignans and chlorogenic acids. Studies are needed to identify the active components of these beverages responsible for their protective effects against the development of DM.
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