Drinking black tea may help protect against type 2 diabetes, but more study is needed to confirm an association.

When researchers analyzed data from 50 countries, they found that the rate of diabetes was lowest in countries where people drank the most black tea.

Type 2 diabetes rates have skyrocketed worldwide in recent decades. It's projected that by 2030 there will be more than 900 million people across the globe with diabetes or with a high risk for developing it.

When researchers used a mathematical model to estimate the impact of drinking black tea on a number of health conditions, they found a link to just one -- diabetes.

Of the countries included in the analysis, black tea drinking was highest in Ireland, the U.K., and Turkey. It was lowest in South Korea, Brazil, and China.

Researcher Ariel Beresniak, MD, PhD, of the mathematical research group Data Mining International in Geneva, Switzerland, says the study shows a consistent relationship between black tea drinking and type 2 diabetes risk. But this study does not prove a cause and effect relationship.

Black tea may protect against diabetes, Beresniak says, but more research is needed to prove this.

"You certainly can't say that on the basis of this study alone, but the findings are consistent with previous studies that have also suggested a link," he says.

The new study was published today in the journal BMJ Open.