Something to keep in mind the next time you find yourself in the produce aisle at the supermarket: apples, blueberries, and grapes, can reduce your risk of developing type 2 diabetes. Whole fruits are what you need, not juices, which actually increase the risk of type 2 diabetes, according to a new study.

The study authors say their results support recommendations to increase consumption of fruits as a way to prevent diabetes, but fruits offer other benefits, too.

Fruits can improve mood and prevent artery-clogging plaque from building up. They help the brain as well.

Whole fruits are what you need, not juices, which actually increase the risk of type 2 diabetes.

“…[I]n previous studies, fruit was not consistently associated with an effect on diabetes risk,” Qi Sun, one of the researchers, told TheDoctor. He and his colleagues suspected that part of the reason for this inconsistency was that different fruits do not have the same effect on diabetes risk.

For example, resveratrol, chlorogenic acid, and anthocyanins have been demonstrated to be beneficial for glucose metabolism in animal studies and human observational studies, Qi explained. Blueberries, some apples, grapes, and raisins are particularly rich in these compounds.

The results were not too surprising, said Qi, because the scientists’ hypothesis was that the variations in the levels of certain phytochemicals, naturally occurring compounds in plants, account for their differing effects on diabetes risk.

One finding was a little surprising, Qi, an assistant professor in the department of nutrition at the Harvard School of Public Health, said. The glycemic index and glycemic load of fruits, two measures of how rapidly blood sugar and blood insulin levels change after consumption of food, do not determine if a fruit is associated with type 2 diabetes risk. Other factors in fruit may affect diabetes risk, but not glycemic index and glycemic load.

The researchers looked at data from food frequency questionnaires distributed every 4 years to women enrolled in the Nurses Health Study I and II and men enrolled in the Health Professionals Follow-Up Study and compared the reports of fruit consumption by those who developed type 2 diabetes to those of people who did not develop diabetes. For every three servings of certain whole fruits consumed per week, particularly apples, grapes and blueberries, the risk of diabetes significantly decreased.

Turn Off The Juice
Type 2 diabetes risk increased with increased consumption of fruit juice. During the juicing process, some of the beneficial natural fiber and phytochemicals are lost, Qi said. Also, fruit juices are fluids, so they can be absorbed more rapidly into the gastrointestinal system versus whole fruits, and subsequently lead to more dramatic changes in blood sugar and blood insulin levels.

Scientific evidence exists that large changes in blood sugar and blood insulin levels after meals may in the long run increase the risk of type 2 diabetes. “I want to stress that this research is not over yet,” said Qi. Scientists definitely need to see more research to determine if other factors in fruits that could further explain their different effects on diabetes risk.

Qi and his colleagues are conducting several studies to further explore the associations between phytochemicals such as resveratrol, flavonoids, and chlorogenic acid, and diabetes risk. “We also hope to extend these associations to persons with chronic conditions such as cardiovascular disease, and to other patient populations such as diabetic patients. ”

The study is published online in the British Medical Journal.