There are no special health benefits of blackberries for people with diabetes. Blackberries have a lot in common with most fruits, which have high amounts of natural fiber and low-to-moderate amounts sugar. What’s more, blackberries are generally harvested when fully ripe, which means they naturally release their sugars slowly when eaten because large swathes of their natural sugar content is bound up in cellulose fibers — this is good for diabetics! On the downside though, blackberry season is limited to early summer into fall.