“An apple a day keeps the doctor away."
This may have originated in 19th-century Wales as "Eat an apple on going to bed, and you'll keep the doctor from earning his bread." Apples are not nutritional powerhouses, but certain compounds in them (notably in their skin) have potential heart-healthy and anti-cancer effects. A BMJ study estimated that if all Britons over 50 ate an apple a day, nearly as many cardiovascular deaths would be averted as by daily statin drugs, with fewer side effects. And a Spanish study in the American Journal of Clinical Nutrition linked even a modest increase in fruit and fiber intake with reduced mortality rates. The most commonly eaten fruit in the study? Apples.
“Early to bed and early to rise makes a man healthy, wealthy, and wise.” This appears in Benjamin Franklin’s Poor Richard’s Almanack, but similar sayings date back to at least the 15th century. Though society tends to think more highly of early birds, some studies have found that night owls are actually more likely to get the worm—at least in terms of scores on certain types of intelligence tests. Research overall has been inconsistent in terms of health and intelligence (and most likely about wealth as well). The important thing is to find the pattern and duration of sleep that work best for you.
“Fresh air impoverishes the doctor.” This old Danish saying is supported by voluminous research showing that polluted air—outdoors and indoors—causes or worsens not only breathing disorders but also cardiovascular disease and other problems. Moreover, spending time outdoors on sunny days can improve mood and fend off winter depression—and sunlight causes the skin to produce vitamin D, which is associated with a wide array of potential health benefits. However, if such advice encourages people to spend lots of time in the sun, that certainly won't "impoverish" dermatologists, who are kept busy treating skin cancer and sun-damaged skin.
“Birds of a feather flock together." This aphorism was given a new twist by a study that found that a social network (that is, flock) is a good predictor of whether a person will be obese or not. It's not just that obese people hang out together, but also that thinner people who have many obese friends are more likely to become obese themselves over the long term, according to the study, published in the New England Journal of Medicine.
“A merry heart does good like a medicine." There's solid support for this insight from the Book of Proverbs, assuming a merry heart means happiness or laughter. Good health is a cause for happiness, of course, but happiness can also enhance health—it's a virtuous circle. What’s more, researchers have found that laughter can have beneficial effects, especially on arteries, blood pressure, and the cardiovascular system in general.