Blueberries and whole fruit may decrease type 2 diabetes risk but fruit juice increase it

A study from Harvard University shows that people that eat whole fruits, and in particular blueberries, have a significantly lower risk of developing type 2 diabetes.
The decrease in risk amongst those eating whole fruits varied from 7% for apples and pears, 12% for grapes and raisins, up to a 26% decrease for those that regularly ate blueberries. Fruits such as apricots, bananas and peaches conferred no significant increase or decrease in risk.
The study also notably showed that the risk of developing type 2 diabetes increased amongst those having greater amounts of fruit juice.
The way the study was run is always important in being able to understand the results. In this study, participants filled in food frequency questionnaires every four years answering questions on how often they ate certain fruits and juices. Over 180,000 people took part in the research with the majority of participants, around 80%, being women.
It should be noted that the study shows no concrete causes as fruit intake was the only part of the diet recorded, therefore the study can only show trends associated with people that eat a higher frequency of certain fruit. Blueberries has had its health properties well publicised and it stands to reason that those picking out blueberries are likely to be those actively looking to maintain a balanced diet and a healthy lifestyle.
The study implies that replacing regular fruit juice consumption for blueberries could reduce the risk of type 2 diabetes by 33% but this calculation is an over-simplification and ignores the fact that those regularly having blueberries could well have been living a healthier lifestyle all round.
The research also highlights some questions over the health status of fruit juices which tend to have a high natural sugar content and a lower vitamin content than fresh fruits. If you regularly consume fruit juice, there is likely to be some benefit in swapping some of your fruit juice consumption for whole fruits and take a look at the same time if any other parts of your diet could be improved at the same time.