This could be many reason to avoid white bread because it's highly processed flour are unhealthy and increase a risk of many diseases
white bread rich in high glycemic index foods that increase depression
white bread contains sugar and hhigh-fiber that gain your weight slowly
white bread high in fiber with lower glycemic index and easily digested that spikes blood sugar level
White bread boost of energy shortly, so eat low fiber food for fuel energy.
White bread contain bad fat so it increase your bad cholesterol