>pretty much every popular health fad has no provable causative effect on health.
Isn't this almost true by definition? If it actually works, it's not a "fad", just "science" or whatever. Advice like "eat more vegetables" and "don't drink alcohol" probably do work, but they're ingrained enough that nobody thinks they're "fads".
The late 1800's health craze centered around Battle Creek, Michigan has had long lasting cultural and dietary impact, but I think most people would still call it a fad, because the core tenants were only popular for a short time.
Besides, the breakfast cereal movement it created quickly devolved from the Kellogg's and Post's original healthy cereals, Corn Flakes and Grape Nuts respectively, into the sugar-laden craze of 1950's cereals. Even Graham crackers were healthy and bland at the time, but we now associate them with cinnamon and sugar.
Isn't this almost true by definition? If it actually works, it's not a "fad", just "science" or whatever. Advice like "eat more vegetables" and "don't drink alcohol" probably do work, but they're ingrained enough that nobody thinks they're "fads".