Whole fruit is better than fruit juice. Three studies of US men and women showed that greater consumption of three specific whole fruits, particularly blueberries, grapes, and apples, was significantly associated with a lower risk of developing type 2 diabetes. But greater fruit juice consumption can increase the risk.
These results support recommendations on increasing consumption of a variety of whole fruits, especially blueberries, grapes, and apples, as a measure for diabetes prevention.
The study was published online in the British Medical Journal on August 29, 2013. The study was conducted by Harvard researchers who examined the dietary habits of more than 187,000 participants and found that people who ate three standard servings a week of blueberries had a 26% lower chance of developing the type 2 diabetes they found. Those eating grapes had a 12% reduced risk and apples cut the chances by 7%. The researchers said these fruits contain high levels of anthocyanins, which have been shown to enhance glucose uptake in mice. Moreover, these fruits contain naturally-occurring polyphenols which are known to have beneficial effects. In the juicing process, only fluid portion of the fruits are taken, which are absorbed more quickly, causing rise of blood sugars as well as insulin levels.
Type 2 diabetes usually appears in people over the age of 40, develops when the body can still make some insulin, but not enough, or when the insulin that is produced does not work properly (known as insulin resistance).
South Asians are at greater risk of it; with less of a habit of eating fruits, it often appears from the age of 25.