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A fruit-rich diet may protect people from diabetes, a new study suggests.

Researchers found that eating whole fruits was significantly associated with a lower risk of type 2 diabetes. However, greater consumption of fruit juices was associated with a higher risk of type 2 diabetes.

"While fruits are recommended as a measure for diabetes prevention, previous studies have found mixed results for total fruit consumption. Our findings provide novel evidence suggesting that certain fruits may be especially beneficial for lowering diabetes risk," senior author Qi Sun, assistant professor in the Department of Nutrition at HSPH and assistant professor at the Channing Division of Network Medicine, Brigham and Women's Hospital, said in a news release.

Researchers looked at data gathered between 1984 and 2008 from 187,382 participants in three long-running studies (Nurses' Health Study, Nurses' Health Study II, and Health Professionals Follow-up Study). Researchers examined overall fruit consumption, and consumption of individual fruits: grapes or raisins; peaches, plums, or apricots; prunes; bananas; cantaloupe; apples or pears; oranges; grapefruit; strawberries; and blueberries. Researchers also looked at consumption of fruit juices.

Overall, 12,198 participants developed diabetes during the study period. Researchers found that people who ate at least two serving each week of certain whole fruits, particularly blueberries, grapes and apples, reduced their risk for type 2 diabetes by as much as 23 percent compared to those who ate less than one serving per month. On the other hand, people who consumed one or more servings of fruit juice each day increased their risk of developing type 2 diabetes by as much as 21 percent.

Researchers found that switching three servings of juice per week for whole fruits would result in a 7 percent reduction in diabetes risk.

While whole fruits' glycemic index (a measure of how rapidly carbohydrates in a food boost blood sugar) was not a significant factor in determining a fruit's association with type 2 diabetes risk, the high glycemic index of fruit juice may explain the positive link between juice consumption and increased diabetes risk, according to researchers.

"Our data further endorse current recommendations on increasing whole fruits, but not fruit juice, as a measure for diabetes prevention," lead author Isao Muraki, research fellow in the Department of Nutrition at HSPH, said in a news release. "And our novel findings may help refine this recommendation to facilitate diabetes prevention."

The findings are published in the journal BMJ (British Medical Journal).