Quote from David on August 1, 2024, 11:37 pm

Up until 1949/1950, at least in North America, much flour was bleached with the agene process, which is another problem with early nutritional science on top of the animals being fed heat-treated casein and other franken foods. From wikipedia citing a French journal from 2008:
"The agene process is a former process for bleaching flour with agene (nitrogen trichloride). The practice was discontinued in 1949 once it became known that agene treated flour caused severe and widespread neurological disorders in humans and dogs.[1]"

Agene bleaching of flour started around 1922 according to the paper below, so its main use was around 1922-1950.

There is an animal study on agene and nerve toxicity from 1947 called:
"WHITE BREAD AND EPILEPSY IN ANIMALS"
https://doi.org/10.1001/jama.1947.02890120011005 (available at sci-hub)

INTRODUCTION:
"The treatment of flour with chemical agents is a widespread commercial practice. In general these chemical agents are applied either for "bleaching" or for "improving" the flour. Common usage has made the term bleaching synonymous for both of these effects. The main reasons for using chemical improvers are that they enable bakers to produce loaves of bread which appeal to the palate, allow millers to use any supply of sound wheat for the production of bread flour with uniform properties and circumvent the waste and spoilage which occur when flour is aged naturally during storage.
  Although flour bleaching was first used widely at the turn of the century, during the past twenty-five years approximately 90 per cent of all white wheat flour milled in North America and in England (among other countries) has been treated with nitrogen trichloride (NC13).1 Flour treated in this way produces a loaf of bread which is well risen, of good volume and symmetry, silky and finely vesiculated and with a smooth crisp crust (fig. 1). When fed to dogs as a major portion of their diet, such bread produces canine epilepsy."

From the "comment" section in the paper:
"The significant possibility that a toxic substance is being offered to the American public in a universal and staple article of diet such as bread, at a time when we are being compelled by present world conditions to increase the cereal content of our diet, makes it imperative that the medical profession as a whole should take on itself the responsibility for investigating, by many different technics and on different species of animals, the wholesomeness and suitability of all processed foods."

PS. In this 1947 study they fed the animals (dogs, cats and monkeys) casein, liver extract and cod liver oil but back then it was agene treated flour (really just the protein component) that put these animals quickly over the top into full-fledge epilepsy.

PSS. I found out about agene treatment of bread from the linked book below where they thanked a company for supplying agene treated G.R. flour on page 10: "Cranfield Bros., Ltd., Ipswich, for supplying Canadian G.R. white flour, specially bleached with agene."

From the 1949 book:
"Vitamin A Requirement Of Human Adults"
https://archive.org/details/vitaminrequireme0000emhu/