I've been reading the book Fear of Food by Harvey Levenstein. It is a fascinating read, chronicling the history of food fears and fads that hit Americans in the 19th and 20th centuries. I have a few quibbles with some of the material in the chapter on "Bacteria and Beef", but overall, good stuff.
One passage showed how at least one version of the Paleo diet had been advanced since the early 1900s for many of the same reasons it is advocated today, almost 100 years later:
Levenstein also chronicles the emergence of food scientists and nutritionists who often had significant effects on dietary fads and public policies. It is remarkable the hubris with which many of these men made dietary advice and public policy, particularly because we now know they were often quite wrong in their scientific knowledge. Whether it was Metchnikoff and Kellogg and their views on autointoxication and the merits of yogurt, or Horace Fletcher's method of chewing to "Fletcherize" food, or Harvey Wiley and his war on benzoate of soda, or Elmer McCollum and his promotion of acidosis, or Russell Wilder's belief that thiamine deficiencies would cause the nation to loose their will to fight the Nazis - there seems to be a continual stream of people willing to use scant evidence to promote their favored cause to promote public health. Not just idly promote - but with often with righteous indignation and certitude of belief. I have no doubt many of these men passionately believed the diets they promoted but that didn't ultimately make them right.
Levenstein writes, in the midst of concern of lack of vitamin consumption in 1941, that
Unfortunately, something similar could be said about how applied science and technology have often been used none too wisely to promote various public policies and best selling books.
It is true that science has progressed and we know more than we used to. One of the things we've hopefully learned is that we often need to exercise a bit of humility.