Smoking gives you lung cancer
The first studies connecting smoking to lung cancer came out as early as 1939, but many doctors contended that cancer was largely due to other factors such as air pollution until the early 1960s.
Bacteria produce ulcers
Australian physicians Robin Warren and Barry Marshall identified the link between Helicobacter pylori and ulcers in 1982, but the medical community maintained that the causes were stress and/or diet until the mid-1990s when the NIH acknowledged the connection.
Aspirin lowers heart attack risk
A California physician named Lawrence Craven first published research showing aspirin’s anti-clogging effect back in 1950, but his practice of prescribing an aspirin a day to keep heart disease away wasn’t widely adopted until about 40 years later.