From Dr. Joseph Mercola:
Berries are among the best fruits on the planet. Not only do they taste great, but they are densely packed with a variety of potent phytochemicals that can do wonders to normalize 
and improve health. They are also high in fiber and relatively low in sugar, so they won’t stimulate severe insulin swings if eaten in moderation.
The best way to eat berries is in their raw, natural state, as heating and freezing can damage antioxidants. However, some antioxidants remain even after heating or freezing.
Fruit juices should be avoided as they contain a large amount of fructose. Each glass of juice, even those with no sugar added, has more sugar than a glass of soda. Although the sugar it contains is fructose, it will still negatively affect your immune system.
As with all fruits, eat berries in moderation. If you eat too many berries the carbohydrates will increase your insulin levels. This is partially compensated for by the fiber in the whole fruit, which helps delay the absorption of sugar. Eating small amounts of whole fruits will not provide tremendous amounts of the natural sugar fructose, however, and therefore should not be a problem for most people.
