You’ve had cassava if you want boba in your milk tea. This vegetable, also known as tapioca, is most commonly grown in equatorial countries and contains hydrogen cyanide, which can contaminate the body if eaten raw or without sufficient cooking time and procedure.
Cassava is available in two flavors: sweet and sour. Sweet cassava has just 20mg of cyanide per root, making it 50 times less lethal than bitter cassava. Even so, if eaten wrongly, it contains enough poison to kill an adult cow on the spot.