Key points from article :
BBC finds 80 videos for unproven cures in 10 different languages.
YouTube algorithm promotes these videos through recommendations.
Professor Justin Stebbing, from Imperial College London, examines some of the claims.
Healthy diet is important - but juices or vegetables can't cure cancer.
Baking soda can be harmful - an Italian doctor was convicted of manslaughter for using it.
Creators and YouTube are making money from adverts.
YouTube says it is removing ads from videos that promote harmful health claims.