I am growing white cabbages and as the cabbage heart develops there are other leaves growing below the heart off the main plant stalk.  Can these leaves be eaten?  I am not referring to a cabbage in which the outer leaves are discarded, say when purchased and the outer leaves are damaged/soiled. 
Found a few places suggesting it's safe (and nutritious) to eat the cabbage stalk/lower leaves:   University of Florida Gardening Know How Sainsbury’s  