Blåbärssoppa is traditionally served to the participants at the ski marathon Vasaloppet, as it is rich in energy. Bilberries have traditionally been used to combat mild gastrointestinal ailments, and in Sweden, blåbärssoppa is often considered suitable food for people with stomach upsets, also because it is energy-rich.
The Swedish word for bilberry, blåbär, literally means "blueberry" but the beverage is not made from the North American blueberry (section Cyanococcus of the genus Vaccinium) but from the bilberry, Vaccinium myrtillus, which grows in the wild throughout Scandinavia and other parts of Europe.
Scandinavian Blueberries also know as Bilberries (Vaccinium myrtillus) and the US blueberries(Vaccinium cyanococcus) have both been used as traditional medicine, however the bilberry has been shown to be far more effective by modern scientific and clinical investigations. This is due to the fact that bilberries contain a significantly higher concentration of the active substances anthocyanins (a form of isoflavonoids) than blueberries, along with a higher antioxidant potential. To date, there is evidence that anthocyanins reduce cell damage caused by oxidative stress, while protecting cardiovascular function, and possessing anti-inflammatory properties. For eye health, bilberry provides many protective effects against vision impairments and blindness. (Source http://www.eyehealth-central.com/bilberry-or-blueberry.html)