Flavonoid is a natural compound mainly found in citrus fruits, berries, onions, parsley and dark chocolate.

“People who ate a higher amount of blueberries or apples, tended to have a low risk of type 2 diabetes,” said An Pan, a research fellow at the Harvard School of Public Health.

Researchers asked study participants to fill out regular questionnaires about how frequently they consumed certain foods and beverages of a standard portion size.

The team found that blueberry-lovers had a 23 percent lower risk of developing type 2 diabetes compared with those who ate no blueberries.

The study also revealed that people who ate five or more apples a week had a 23 percent lower risk compared with those who did not consume the fruit.

Although fruit sugar raises blood glucose levels rapidly, other substances in fruit such as fibers and pectin may have diabetes-related benefits, said Dr. Loren Greene, professor of medicine at New York University.

Greene suggested people eat whole fruits rather than fruit juices because the juice alone increases the risk of diabetes.

According to the American Diabetes Association, approximately 26 million Americans suffer from diabetes.