An apple a day keeps the doctor away
Historically apples have always been considered healthy food. For many centuries they were one of the few fruits that were readily and freely available to everyone in England. In recent years we discovered that the high vitamin C and fiber content in the fruit makes it a very healthy food.
Referring to your health, this proverb is talking about living a healthy lifestyle in order to avoid illness. Whilst it is not actually advising that eating a single apple each day will prevent you from ever having to visit a doctor, it means that by living a healthy life, doctors visits will be less frequent. For example, if you eat plenty of fruit and vegetable and exercise regularly, you will be less likely to fall prey to bad health.
Example:
An attractive woman was dating two guys, one is a doctor, another is an engineer.
The doctor often brought in luxury gifts, while as the engineering kept giving the woman an apple everyday since he believed "an apple a day keeps....."
