Three studies by US researchers have found that eating at least three servings a week of whole fruits is associated with a reduced risk of type 2 diabetes.
Different types of fruit had different associated reductions in diabetes risk, with NHS Choices reporting that blueberries were the best with an additional three servings a week of these was associated with a 26% reduction in diabetes risk.
Eating more grapes and raisins; prunes; apples and pears; bananas and grapefruits was also associated with reduced diabetes risk, although the reductions in risk seen were smaller. Drinking three portions of fruit juice a week was associated with an increase in diabetes risk of around 8%.
The results of this study support the benefits of eating at least five portions of fruit and vegetables a day, with only one portion of juice a day counting towards your five portions.
The study was carried out by researchers from the Harvard School of Public Health and other research centres in the US, UK and Singapore. It was funded by the US National Institutes of Health, and one author was supported by the National Heart, Lung, and Blood Institute.
The researchers say that although a diet including more fruit is recommended to reduce risk of many chronic diseases, including type 2 diabetes, observational studies looking at the link have found mixed results.
One possible explanation is that different fruits with different fibre, nutrient and antioxidant contents and different glycaemic indices (how quickly a food can raise blood sugar levels) could have different effects.
Prospective cohort studies such as this are the most feasible way to study the long-term effects of diet on health outcomes. Randomised controlled trials of diet would provide more reliable results, but are not feasible as people are unlikely to agree to stick to a highly regulated diet for a long period (sometimes up to 25 years) just for the purposes of a study.