Seth Roberts looks at the glacially slow conquest of scurvy:
In a paper called “Innovation and Evaluation” (gated), Frederick Mosteller, a professor of statistics at Harvard, noted how long it took. In 1601, James Lancaster, a sea captain, did an experiment involving four ships on a long voyage. Men on one ship got lemon juice, men on the other three ships did not. The men given lemon juice were far less likely to get scurvy. In 1747, James Lind, a doctor, compared six purported cures for scurvy. Lemons and oranges (one cure) were much better than the other five (as Lind expected). In 1795 the British Navy started using citrus juice regularly and wiped out scurvy on their ships. In 1865, the British Board of Trade recommended citrus juice for commercial ships. It took more than 200 years for a simple and effective remedy — discovered before Lancaster — to spread widely.
Why is this relevant today?
The sailors at risk of scurvy did not control what they ate. The people who controlled what they ate never got scurvy. Sure, the people who controlled what sailors ate did not want them to get scurvy (high rates of scurvy were a big problem) but they also had other concerns. The lesson I draw from this story is do not let anyone else (doctor, expert, etc.) solve your health problems for you. Sure, other people, as part of their job, will sell you something, provide advice, write a prescription, provide therapy, do surgery, whatever. It might work. They want to help you — the more they help you, the better they look, the more business they attract. But it is entirely possible, this bit of history teaches, that they are slow on the uptake or have conflicts of interest and a much better solution is available.