(p. 67) . . . : The Nature of Bread, Honestly and Dishonestly Made, by Joseph Manning, M.D., . . . reported that it was common for bakers to add bean meal, chalk, white lead, slaked lime, and bone ash to every loaf they made.
These assertions are routinely reported as fact, even though it was demonstrated pretty conclusively over seventy years ago by Frederick A. Filby, in his classic work Food Adulteration (1934), that the claims could not possibly be true. Filby took the interesting and obvious step of baking loaves of bread using the accused adulterants in the manner and proportions described. In every case but one the bread was either as hard as (p. 68) concrete or failed to set at all, and nearly all the loaves smelled or tasted disgusting. Several needed more baking time than conventional loaves and so were actually more expensive to produce. Not one of the adulterated loaves was edible.
Source:
Bryson, Bill. At Home: A Short History of Private Life. New York: Doubleday, 2010.
(Note: ellipses added; italics in original.)