As I mentioned in my post about Quick Sugar-Free Blackberry Chia Seed Jam, some nutritionists consider blackberries to be the new "superfood." Bursting with antioxidants, blackberries are rich in Vitamin C. They're also an excellent source of fiber and Vitamins K and A. Not only that, they may even promote brain health! And with only 5 net carbs in 100 grams, blackberries are a good choice for a low-carb diet.