Bilberry leaf extract has been historically used to help lower blood sugar in diabetes sufferers. You will also find that bilberry helps with diarrhea, menstrual cramps and a variety of circulatory problems. Bilberry may also assist with night vision, glaucoma, cataracts, sore throats, stomach ulcers, fibrocystic breast disease and atherosclerosis. According to the University of Maryland Medical Center, bilberry also contains vitamin C.