Anything which cannot be taken as a full meal is not good for health and either should not be taken or taken in a small amount.
For example, we never eat a breakfast of onion or garlic or radish. These are the items which either should not be taken or eaten only in small quantity only as addition to other full meal.
Onion is good for health and has anti-cholesterol properties and also blood thinning properties, yet it is consumed only in small quantity. In Vedic language, onion has both rajasik and tamasik promoting properties, which make a person more aggressive and dull.