Coffee intake was associated with a lower incidence of type 2 diabetes

A new systematic review has summarised the findings of observational research into the association between coffee and type 2 diabetes.

Clinical question:

Is coffee intake associated with an increased risk of developing diabetes?

The reviewers wanted to explore whether different amounts of coffee intake affected the risk differently.

The evidence:

The reviewers searched MEDLINE for cohort studies published between 2001 and 2011.  They combined the data from 13 studies, they found that:

Participants who drank 4 to 6 cups and more than 6 to 7 cups of coffee per day had a lower risk of type 2 diabetes compared with those who drank less than 2 cups per day.

Appraisal hints:

Users of this research should consider:

  • The literature search was not exahustive and probably missed important studies.
  • It’s not clear whether the reviewers rigorously evaluated the quality of the individual studies.
  • Did they adjust the data for other important confounders?
  • It’s not clear whether the review included both retrospective and prospective studies.
  • Were the participants assembled at equivalent stages or levels of risk of developing diabetes?
  • Were the findings consistent from one study to another?
  • We can’t say from this review of observational research that coffee reduces the risk of type 2 diabetes.


Muley A, Muley P, Shah M.  Coffee to Reduce Risk of Type 2 Diabetes? : A Systematic Review. Curr Diabetes Rev. 2012 Apr 12. [Epub ahead of print]