Es un dicho inglés que tiene una traducción muy variada en español. «Una manzana al día mantiene al médico en la lejanía», o «Una manzana al día aleja al médico de tu vida». Mi madre decía algo parecido «Una manzana por la mañana aleja al médico de la cama».
This is a traditional saying in English particularly aimed at making children aware of the importance of eating fruit, in this case apples, on a daily basis. Some years ago though, different reports said it wasn’t true that the daily consumption of apples was as healthy as the saying goes. However, recent evidence says apples contain anti-cancer properties, therefore eating apples regularly may keep unwanted health problems away.