The berry traditionally associated with night-vision support and diarrhea remedies is bilberry (*Vaccinium myrtillus*).
Bilberry is a low-growing Eurasian shrub related to blueberries and cranberries. Its dark blue berries are rich in anthocyanins, pigments that give the fruit its intense color. Traditional medicine used the fresh or dried fruit in preparations for digestive complaints, including diarrhea, while bilberry extracts later became especially famous for claims about improving night vision.
The night-vision story became widely popular during the Second World War, when a legend claimed that British Royal Air Force pilots ate bilberry jam to see better at night. However, systematic reviews have found no convincing evidence that bilberry consumption improves night vision in healthy people. The traditional claim is therefore different from a proven clinical effect.
Bilberry is commonly confused with the North American blueberry. Bilberries usually have dark flesh that stains the fingers and tongue, whereas many cultivated blueberries have pale, less strongly colored flesh. “Bilberry” can also refer to several related *Vaccinium* species, but *V. myrtillus* is the standard common bilberry.