Coffee may reduce the risk of type 2 diabetes

Coffee may reduce the risk of type 2 diabetes
After observational studies hinted that drinking coffee reduced the risk of type 2 diabetes, researchers investigated this attractive possibility by systematically reviewing the best available data. They found a strong and consistent link between habitual coffee drinking and a lower incidence of type 2 diabetes. In nine cohort studies combined (n = 193 473) people in the highest or second highest categories for coffee drinking (3 6 cups/day and 4-6 cups/day) were about a third less likely to develop diabetes than people in the lowest category (£ 2 cups/day) (relative risks 0.65, 95% confidence interval 0.54 to 0.78, and 0.72, 0.62 to 0.83). The association stood firm after adjustment for confounding factors, including smoking and obesity. It was also consistent across five cross sectional studies from Japan, Spain, Sweden, and the Netherlands.
These findings look convincing, but it's much too early to start telling patients to drink more coffee, say the authors. Because of the nature of the studies, there's still a chance the association isn't real (caused instead by bias or confounding) or causal (early diabetes might alter coffee drinking habits). Even if it is both, we need to find out more about how and why coffee alters glucose metabolism before concluding that it's good prophylaxis against diabetes.