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Here are the top eight most common medical myths that you can officially ignore.
1. You lose most of your body heat through your head.
“Wear a hat—you’ll catch a cold!” says your mother as you sprint out of the house. The myth that heat is lost from the head more than any other part of the body is 
In the study, volunteers were dressed in Arctic survival suits and exposed to extreme cold. The study concluded that the human body part that lost the most amount of heat was the head.
What the report failed to mention was that the head was the only body part that was exposed to the elements during the experiment. Thus, its findings are understandable—but skewed.
In actuality, the human body loses only 10 percent of heat through the head—the other 90 percent is emitted from other parts of the body.
2. You need to drink eight glasses of water a day.
No one is exactly sure where the theory that the body needs eight glasses of water a day came from, but it may have gotten a start in 1945 when the Food and Nutrition Board of the National Research Council announced that the body needs 2.5 liters (approximately equivalent to eight glasses) of water daily.
What the agency meant, however, was that the body needs the equivalent of that amount of water from whatever food and liquids are ingested throughout the day. Somewhere along the way, this information got misinterpreted to mean adults need to drink eight glasses of water a day in addition to whatever else they’re eating or drinking.
3. You should wait an hour after eating before you go swimming.
Do you remember sitting impatiently by the pool as you tried to will your body to digest your recently eaten lunch quicker so that you could hop back in the pool ASAP?
In hopes of saving future generations from after-meal, poolside anguish, we’re excited to share that research shows there’s no reason to avoid swimming for any period of time after eating.
So go ahead and take a dip.
Although some people experience discomfort when they swim on a full stomach, doing so shouldn’t induce cramping or nausea—and it certainly won’t result in any type of serious or life-threatening afflictions.
4. Gum stays in your belly forever.
Ever swallow your gum by mistake? If you’re like us, as soon as you’ve done so, you’re overcome by instant panic that it’ll remain in your belly forever (or for at least seven years).
It’s true that your body can’t digest gum, but that doesn’t mean it just sits in your stomach. Gum that gets ingested eventually passes through your digestive tract just like the other things you eat.
In fact, it simply moves along with the other food in your gut and gets eliminated in the same fashion as whatever else your body didn’t use.
The main reason doctors recommend that kids not swallow gum is that if extraordinary amounts of it are consumed in a short period (especially if a child is prone to constipation) the gum bolus can result in intestinal blockage. Although rare, it has been known to happen.
5. Cracking your knuckles will give you arthritis.
We’ve all done it—and felt guilty about it. Every crack is a reminder of the times well-meaning bystanders told us that if we continue to crack our knuckles, we’ll inevitably end up with arthritis. But studies show there’s no link between the compulsive joint-cracking behavior and the painful condition. During a satisfying crack, the bones in your fingers move apart, forming a cavity that causes that telltale cracking or popping sound.
. The study followed and x-rayed patients over a five-year period, separating those whose scans confirmed the presence of arthritis into one group and those without arthritis into another.
Surprisingly, it turned out that participants who reported no knuckle-cracking behavior had slightly higher rates of arthritis (18.1 percent versus 21.5 percent) than those who admitted to cracking their knuckles.
Arthritis can be caused by normal wear and tear of the joints, an infection or injury, or an autoimmune disorder. But anxiety-ridden knuckle-crackers can rest easy knowing that their nervous habit is no more dangerous to their health than nail biting or foot tapping.
6. Sitting too close to the TV ruins your eyesight.
When television sets were first introduced, some color models emitted high amounts of radiation that could cause eye damage. This led experts to recommend that adults and children sit as far away as possible from screens.
However, TV and computer monitor safety has been regulated since the ’60s.
So, even though sitting ridiculously close to a screen makes your eyes work harder, it won’t do any permanent damage to them.
Same goes for reading or doing work in the dark. The lack of light might result in eyestrain, but overall, ophthalmologists agree that it’s genetics and age that cause your eyesight to go, not your late-night reading habit.
7. Eating at night makes you fat.
Feeling guilty about your late-night snacking habit? Let us put your mind at ease! Studies show that it doesn’t matter what time of day that you eat as long as you maintain the appropriate calories eaten to calories burned ratio.
The secret of weight gain and weight loss lies in simple mathematics —you must burn as many calories as you eat in order to stay the same weight. If you eat more and exercise less, you’ll gain weight.
Conversely, if you eat less and exercise more, you’ll lose weight.
It doesn’t matter what time you eat your meals, although studies do show that those who snack at night, have a tendency to mindlessly eat with disregard for serving size. This may cause them to eat more than they realize. If you’re a nighttime snacker, keep your calories in check by pouring a serving size of your late-night meal and
8. Sugar makes kids hyperactive.
Bad news for parents! Your child’s restless, unruly behavior can no longer be blamed on their high-sugar snacks.
Research studying how children reacted to diets containing different amounts of sugar found that no amount of sugar (artificial or natural) affected their behavior—not even in participants diagnosed with attention deficit–hyperactivity disorder.
Where a noticeable response did occur was in the parents.
When told that their children were given sugar (even if they hadn’t been), parents automatically believed their children were acting differently even though they were not.