From Happy Accidents, Seredipity in Modern Medical Breakthroughs:

Doctors typically treated ulcers by initially ordering changes in a patient’s diet, in an attempt to protect the stomach walls from its acid. The Sippy diet, introduced by Chicago physician Bertram W. Sippy in 1915, was practiced into the 1970’s. Sippy called for three ounces of a milk-and-cream mixture every hours from 7:00 AM until 7:00 PM, and one soft egg and three ounces of cereal three times a day. Cream soups of various kinds and other soft foods could be substituted now and then, as desired. Accompanied by large doses of magnesia powder and sodium bicarbonate powder, such “feelings,” as meals were known, would continue for years — if not for life.

Unfortunately, the intake of food brings about not only increased saliva but also the production of stomach acid in preparation for digestion. The Sippy method was thus rarely unsuccessful because, though doctors didn’t realize it, the diet actually increased level of stomach acid and therefore aggravated the symptoms of ulcers.

The fact that this falsely based approach nonetheless persisted for six decades illustrates the unfortunate fact that conventional wisdom once adopted remains stuck in place even when it flies in the face of reality