From the Manufacturer:
Bilberry (Vaccinium myrtillus) is also known in some parts of the U.S. as huckleberry. During World War II, British pilots ate bilberries before their night flights to nutritionally support their vision. Bilberry also supports the circulatory system. Its active constituents include anthocyanins, which are strong antioxidants. Nature’s Sunshine uses 40 mg of bilberry fruit standardized to 25 percent anthocyanins. Bilberry should be used over time in order for the body to best assimilate its unique nutritional properties