Barium is a soft white metal. Doctors use barium sulphate to help them take X-rays of the digestive system. Before an X-ray you either have the barium as a white liquid drink (known as a barium meal or barium swallow), or you have it put into your back passage (a barium enema). X-rays cannot go through barium, so the outline of the stomach or bowel shows up on the X-ray picture.