Whole Fruits Linked to Lower Diabetes Risk

An apple a day keeps the doctor away, according to the old adage. But could it keep diabetes away too? Perhaps. Eating more whole fruits—particularly apples, blueberries, and grapes—was significantly associated with a lower risk of type 2 diabetes, according to new research from the Harvard School of Public Health. Meanwhile, greater consumption of fruit juices was linked to a higher risk of type 2 diabetes.

This is the first study to explicitly examine the effects of individual fruits in relation to diabetes risk. Researchers looked at data collected between 1984 and 2008 from 187,382 participants who were enrolled in three long-range, prospective trials—the Nurses’ Health Study, Nurses’ Health Study II, and Health Professionals Follow-up Study. They excluded participants who reported a diagnosis of diabetes, cardiovascular disease, or cancer. During the study period, 12,198 enrollees (6.5%) developed diabetes.

Investigators looked at overall fruit intake, as well as consumption of individual fruits:

• Grapes or raisins.

• Peaches, plums, or apricots.

• Prunes.

• Bananas.

• Cantaloupe.

• Apples or pears.

• Oranges.

• Grapefruit.

• Strawberries.

• Blueberries.

They also looked at consumption of apple, orange, grapefruit, and “other” fruit juices. Participants who ate at least two servings of certain whole fruits each week—blueberries, grapes, and apples, in particular—reduced their risk for type 2 diabetes by as much as 23%, compared to those who ate less than one serving per month. On the other hand, those who drank one or more servings of fruit juice each day increased their risk of developing type 2 diabetes by as much as 21%. Swapping three servings of juice per week for whole fruits would reduce diabetes risk by 7%, the researchers found.

While blueberries, grapes, and apples may have some particular health benefits, other fruits studied are not necessarily harmful. “Our study did find that increased consumption of total fruits was also associated with lower diabetes risk,” said senior author Qi Sun, ScD, MMS, MD, assistant professor in the Department of Nutrition at Harvard School of Public Health. “So, overall, I think it’s still reasonable for physicians to recommend increasing consumption of fresh, whole fruits to their patients to help prevent chronic diseases.”  

The authors believe that the beneficial effects seen with particular fruits could be attributed to specific components, but they need more research to determine which of these components influence diabetes risk. “It also remains an unanswered question regarding whether certain fruits should be avoided among diabetes patients to facilitate blood sugar control,” Dr Sun said. Future research will be needed to determine if there is any connection.

“The take-home message is to increase consumption of fresh whole fruits, rather than fruit juices, to help diabetes prevention,” Dr Sun said. “But eating more fruits is just one piece of the whole puzzle.” He recommends that primary care providers encourage patients to take a comprehensive approach to minimize their diabetes risk overall—observing a healthy diet with a high composition of fruits, vegetables, and whole grains, supplemented by nuts, legumes, and fish, and practicing a healthy lifestyle that includes regularly engaging in moderate to vigorous exercise, abstaining from tobacco products, drinking alcohol in moderation, and maintaining an adequate body weight.

―Colleen Mullarkey

Reference

Muraki I, Imamura F, Manson JE, Hu FB, Willett WC, van Dam RM, et al. Fruit consumption and risk of type 2 diabetes: results from three prospective longitudinal cohort studies. BMJ 2013; 347:f5001.