The bleaching agent, Chlorine dioxide, used to bleach flour is reported to produce diabetes-causing contaminant alloxan[1] when reacting with the proteins contained in flour.
Studies show that alloxan, the chemical that makes white flour look "clean" and "beautiful," destroys the beta cells of the pancreas. You may be devastating your pancreas and putting yourself at risk for diabetes, all for the sake of eating "beautiful" bleached flour. If you eat flour, your best choice is unbleached.
See also: flour treatment agents