...It took more than 200 years for a simple and effective remedy [for scurvy]... to spread widely.I'd been meaning to do a post along these lines after reading this lengthy account of the battle against scurvy. Now I don't have to.
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....
The cure for scurvy, of course, is to have an adequate intake of vitamin C. Lest you think that it would take that long in the modern era to determine the adequate intake of a vitamin that might be related to illness, I direct you to this post:
"What the report boils down to is: 'In 100 years, since we started adding vitamin D to food, we've never bothered to figure out what the "natural" level should be.'"Caveat emptor.