“An apple a day keeps the doctor away” is a type of idiom in the English language meaning that maintaining regular, healthy habits helps to prevent illness. Unlike many sayings, this phrase can be interpreted literally in some cases. Apples are one of the healthiest foods available and their regular consumption is linked to a reduced risk of a variety of illnesses. It is thought that the idiom originated in Wales during the 1860s, but, in Rustic Speech and Folk-lore, Elizabeth Wright first used the modern version of the phrase in 1913, which added to its fame. It was then widely circulated throughout the century and still remains popular.
Idioms add color to the English language, but these sayings are generally not meant to be taken literally though they do tend to have double-meanings. “An apple a day keeps the doctor away” originally implied that keeping healthy will require less frequent visits from a medical professional. Taken literally, just eating an apple every day won’t keep a person from ever needing to see a doctor. What the phrase does imply is that eating well will keep a person healthier.
There are lessons to be learned from the phrase. All apples contain antioxidants, vitamins, and minerals, as well as fiber. The fruit also contains vitamin C, which is essential for boosting the immune system, helping the body treat wounds, and maintaining muscles. This type of vitamin is also known for its antioxidant properties, which might help to prevent free radicals from building up in the body that can destroy healthy cells and lead to cancer or other chronic diseases.
The nutritional value of the fruit may be enough to claim that an apple a day keeps the doctor away. It's linked to an increased level of high-density lipoproteins (HDL) cholesterol. This type of cholesterol prevents the build-up of plaque in the arteries. Apples can also decrease low-density lipoproteins (LDL) cholesterol, which is infamous for clogging the arteries and leading to heart disease.
While this idiom is sometimes used by some parents to get their children to eat healthier, it is unlikely that eating an apple every day is enough to literally keep the doctor away. Eating daily sources of fruits can help to keep a person healthy, however, which is what the saying implies. It is unlikely that a person will never need to visit a medical professional, but adopting a healthier lifestyle might reduce the number of visits needed.