Some health rules are followed religiously, but really have no medical or scientific foundation at all. Here are 13 popular rules that aren't as hard-and-fast as you might think.
Don't crack your knuckles. The myth is that this habit will cause arthritis. It may be annoying, but no medical studies prove cracking or popping your fingers will lead to arthritis.
Don't go outside with wet hair. It may make you feel chilly (wet hair doesn't insulate well), but it won't make you sick. Colds are caused by a virus that is usually spread by droplets from someone's cough or sneeze.
Drink eight cups of water a day. As long as you're drinking enough so that you don't feel thirsty, you urinate often, and your urine is nearly colorless, you're probably getting enough water.
Don't swim after you eat. There's no evidence that this causes cramps, which could possibly lead to drowning. While it's true that eating diverts some blood to the digestive system, most experts agree your body can still provide enough blood and oxygen during exercise to keep cramps from happening.
Avoid reading in dim light. You may get a headache and strain your eyes, but experts say poor lighting will not cause permanent damage to your eyesight. Ditto for sitting too close to a television or computer screen.
Use birth control that follows your monthly cycle. Traditional birth control pills are based on a 28-day cycle. In the past, doctors sometimes adjusted the dosage for women with painful or heavy periods. But with the advent of extended-cycle birth control pills, you can skip your period altogether or have it just a few times a year.
Sugar makes kids hyper. While too much of it will cause teeth problems, it’s a common myth that sugar creates hyperactivity in children.
The 'five-second' rule. We’ve all heard this one when someone scoops food off the floor, as if germs stand by with a stopwatch to wait to latch onto food.
Feed a cold, starve a fever. This has been an English wives tale for centuries, but there’s no concrete evidence to support it. When it comes to illness, drinking plenty of fluids is key to a quick recovery.
Coffee makes you dehydrated. People living in warm climates are usually warned not to consume too much caffeine because of its diuretic properties, which could lead to dehydration. A recent study showed that people who drank decaffeinated beverages only had a three percent difference in water retention, thus showing that caffeine and caffeinated beverages don’t cause dehydration.
You need eight hours of sleep each night. Not everyone needs eight hours of sleep a night. Some people run fine on six while others can barely function without nine. In fact, there’s historical evidence that humans used to sleep in intervals: two hours at dusk, a two-hour waking period, and then a second sleep. The amount of sleep you need varies on a variety of factors, including illness, stress, physical activity, and more. As a good rule, if you awake feeling tired, you probably need more or better sleep.
Warm milk helps you sleep. Yes, milk contains tryptophan, the same sedative found in turkey, but you’d have to drink a lot to knock you out for the night. The response people feel from it is entirely psychological, so it can help you fall asleep if you think it will.
Gum stays in your stomach for seven years. Every child who has swallowed his gum has heard this one. Chewing gum, just like anything else you swallow, will get picked up by the fluids and other food in your stomach and moved through digestion in just a few days.
A 2,000-degree river of lava could swallow a dozen Hawaiian homes in the next day or two -- and there's nothing that can be done to stop it. Take a look at images as the molten rock from the Kilauea Volcano creeps toward Pahoa.