A new study from the Harvard School of Public Health found that people who ate a higher amount of blueberries or apples were 23 percent less likely to develop type 2 diabetes.
These fruits contain flavonoids, natural compounds found in certain fruits, vegetables, legumes, nuts, tea and red wine. Previous studies have linked their heath benefits to a lower risk of high blood pressure, heart disease, stroke and cancer.
Type 2 diabetes is caused by a defect in the body's ability to produce or use insulin, a hormone that clears glucose from the blood directing it to cells where it’s used for energy. The disease can often be managed by making changes to diet and exercise.
For the study, researchers tracked the diet habits of approximately 200,000 men and women for up to 24 years. The participants filled out regular questionnaires about how often they consumed certain foods and beverages. None had diabetes at the start of the study.
The lightest blueberry eaters in the study reported getting less than one serving (half a cup) of the fruit per month, while the highest blueberry consumers had two or more servings (at least one cup) per week.
Those who consumed the most blueberries had a 23 percent lower risk of developing type 2 diabetes compared with those who ate no blueberries. People who ate five or more apples a week also had a 23 percent lower risk compared with those who didn't eat apples. These results were found after accounting for other risk factors, such as body weight, cigarette smoking and a family history of diabetes.
The researchers suggested that certain flavonoids found in those fruits might play a role in their beneficial effect on diabetes risk.
While fruit sugar raises blood glucose levels, other substances in fruit such as fibers and pectin may help guard against diabetes, say researchers.
Keep in mind this study assessed participants intake of whole fruit – rich in fibre – not fruit juice. Studies suggest that drinking fruit juice may increase the risk of diabetes.
SOURCE: American Journal of Clinical Nutrition, online February 22, 2012.