Eating more whole fruits, particularly blueberries, grapes and apples is significantly associated with a lower risk of type 2 diabetes, according to a new study.
However, greater consumption of fruit juices is associated with a higher risk of type 2 diabetes, researchers led by Harvard School of Public Health (HSPH) found.
"While fruits are recommended as a measure for diabetes prevention, previous studies have found mixed results for total fruit consumption," said 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.
"Our findings provide novel evidence suggesting that certain fruits may be especially beneficial for lowering diabetes risk," Sun said.
The researchers examined 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).
Participants who reported a diagnosis of diabetes, cardiovascular disease, or cancer at enrollment were excluded. Results showed that 12,198 participants (6.5 per cent) developed diabetes during the study period.
The researchers looked at overall fruit consumption, as well as consumption of individual fruits: grapes or raisins; peaches, plums, or apricots; prunes; bananas; cantaloupe; apples or pears; oranges; grapefruit; strawberries; and blueberries. They also looked at consumption of apple, orange, grapefruit, and "other" fruit juices.
People who ate at least two servings each week of certain whole fruits - particularly blueberries, grapes, and apples - reduced their risk for type 2 diabetes by as much as 23 per cent in comparison to those who ate less than one serving per month.
Conversely, those who consumed one or more servings of fruit juice each day increased their risk of developing type 2 diabetes by as much as 21 per cent.
The researchers found that swapping three servings of juice per week for whole fruits would result in a 7 per cent reduction in diabetes risk.
The fruits' glycemic index (a measure of how rapidly carbohydrates in a food boost blood sugar) did not prove to be a significant factor in determining a fruit's association with type 2 diabetes risk.
However, the high glycemic index of fruit juice – which passes through the digestive system more rapidly than fibre-rich fruit - may explain the positive link between juice consumption and increased diabetes risk, researchers said.
"Our data further endorse current recommendations on increasing whole fruits, but not fruit juice, as a measure for diabetes prevention," said lead author Isao