I think moderation is key?...I have 11 chickens and feed a small bag 4x a week of everything including potatoes asparagus, foods including onion and garlic. When they free range they eat honeysuckle. Eggs taste the same :) ..I dunno..works for me
I was feeding mine scraps at 16 weeks they are laying now. It is important that you still feed them grower (if lot laying yet) then the scraps (as previous posters have stated). This way they are getting the proper nutrition. I tend to feed layer in the morning then scraps a couple of hours...