An apple a day keeps the doctor away
Since I was a little kid Ive always heard the saying that an apple a day keeps the doctor away Im sure my mother or father told it to me at some point. I dont use the proverb much myself anymore since my kids are older now but I used to and I think the message of eating healthy is valid and important. The rhyme would be used to convince children to eat their fruits and vegetables by scaring them with a doctors visit. The proverbial message is a sort of legend because children do believe it to be true but the rhyme itself is also legendary because it is so well known and used.
Because the proverb rhymes, there is an indication that the main audience for it would be children. Its short, easy to remember and rhyming. In a way, this proverbial scare tactic is folk medicine as well because it is a practical and daily exercise of doing something good for your body to prevent illness. The proverb could say Eat Vitamins and avoid illness but that doesnt even compare to the power of an apple a day keeps the doctor away!
Proverbs that teach a lesson or impart wisdom are sustainable because they tend to be passed down because a valuable lesson can be taught very simply and accessibly. Parents can share this proverb with their children without having to go into detail about vitamins and sugar content because for children this proverb explains it in a straightforward and undemanding way.