People who drank more than three to four cups of tea had a one-fifth lower risk of developing Type 2 diabetes than those who drank no tea, according to data reviewed for a recent study. (Larry Crowe/Associated Press)

People who drink more coffee or tea, regardless of whether it's caffeinated, seem to have a lower risk of developing Type 2 diabetes compared with people who don't drink any of the beverages, new research suggests.

Researchers looked at 18 studies involving 457,922 participants between 1966 and 2009 on the link between coffee consumption and diabetes, including six that looked at decaffeinated coffee and seven that looked at tea.

The data was analyzed by Rachel Huxley of the George Institute for International Health, University of Sydney, Australia, and colleagues.

On average, they found that each cup of coffee per day reduced the risk by about seven per cent, after adjusting for other factors, such as age and sex.

In Monday's issue of Archives of Internal Medicine, the researchers concluded:

• People who drank three to four cups per day had an approximately 25 per cent lower risk than those who drank between zero and two cups per day.
• Those who drank more than three cups of decaf coffee a day had about a one-third lower risk of diabetes.
• Those who drank more than three to four cups of tea had a one-fifth lower risk than those who drank no tea.

Antioxidants protective?

Since decaffeinated coffee was also associated with lower diabetes risks, the researchers speculated that other compounds in the drinks, such as magnesium or antioxidants, might be involved.

By 2025, about 380 million people worldwide will be affected by Type 2 diabetes, according to the International Diabetes Foundation.

Huxley and the other researchers said that someday, people at greatest risk for Type 2 diabetes might be advised to increase their consumption of tea and coffee in addition to becoming more physically active and losing weight, the researchers said.

Before that can happen, however, more research is needed to take into account whether tea drinkers are more health conscious than coffee drinkers in general.

And since only 20 per cent of the studies reviewed were from non-white populations, it is not known how the findings might apply to other ethnic groups.

Previous research suggested caffeine may increase susceptibility to Type 2 diabetes in people who are obese.

The latest study was supported by the National Heart Foundation of Australia, the National Health and Medical Research Council of Australia; a Research Career Development Fellowship from the U.K. Wellcome Trust; and a research grant from Institut Servier, France and Assistance Publique-Hopitaux de Paris.