 Depending on the variety , lettuce is an excellent source ( 20 % of the Daily Value , DV , or higher ) of vitamin K ( 97 % DV ) and vitamin A ( 21 % DV ) ( table ) , with higher concentrations of the <unk> A compound , beta @-@ carotene , found in darker green lettuces , such as Romaine . With the exception of the iceberg variety , lettuce is also a good source ( 10 @-@ 19 % DV ) of folate and iron ( table ) . 
