They found that people who drank three to four cups of coffee per day were a quarter less likely to develop type 2 diabetes than those who drank none or fewer than two cups of coffee a day. And for every additional cup of coffee drunk, there was a seven percent reduction in a person's risk of developing type 2 diabetes.
For people who had decaffeinated coffee , they found that having three to four cups a day reduced their risk of developing type 2 diabetes by a third when compared with non-decaf drinkers. For people drinking three to four cups of tea, their risk was reduced by a fifth when compared with non-tea drinkers.
According to the researchers, these findings show that the protective effect of coffee and tea is unlikely to be solely down to caffeine, rather due to a combination of chemicals in these drinks, such as magnesium and antioxidants (lignans and chlorogenic). It is thought that these chemicals increase insulin sensitivity in the body, preventing a build up of glucose in the bloodstream. When there is too much glucose in the bloodstream, the body is unable to produce enough insulin to cope, leading to type 2 diabetes. However, the studies the researchers looked at did not measure levels of glucose or insulin sensitivity in the body so they are only able to speculate on this.
Dr Annabel Bentley, assistant medical director for Bupa, commented: 'This research does not mean that everyone should increase the amount of tea and coffee they drink. The figures are not generalisable to everyone worldwide.