roughage

Originally (archaic), garbage, rubbish, or waste; later (agriculture) the portions of a crop which are discarded, such as husks, stalks, etc.; also, agricultural waste such as weeds.

Coarse or rough plant material such as hay and silage used as animal fodder.

Substances, generally of plant origin, consisting mostly of complex carbohydrates which are undigested when eaten by humans, and which therefore help the passage of food and waste through the alimentary tract; dietary fibre.

I keep telling her not to eat all that roughage for brekky; prunes, bran, and baked beans.