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10 Health ‘Facts’ That Are No Longer True

Think you know what's best for your body? Maybe not as well as you think. Science has proved these bits of conventional wisdom wrong.

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What’s new? Only everything

For as long as scientists have been studying the human body, you’d think they’d have it pretty well figured out. But faster than Halloween candy can appear on store shelves in September, new research uncovers some mind-blowing truth that changes everything. (Once upon a time, doctors recommended smoking—really.) As these debunked “facts” prove, when it comes to the wonders of the human body, we’re still learning. Read about 20 “facts” you learned in school that are no longer true.

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Not true: Vaccines are dangerous

Hopefully, you’ve stopped believing this—or never did, since the theory that vaccines cause autism was always a myth. Plenty of people believed that the shots were risky because of thimerosal, a preservative in some vaccines. However, thimerosal contains a type of mercury that the body can easily clear (and only tiny amounts are used). Even though experts consider it to be extremely safe, manufacturers nonetheless have reduced or eliminated its use. Still, worries about vaccines continue to pop up with alarming frequency, says Purvi Parikh, MD, an allergist and immunologist with the Allergy & Asthma Network. In fact, so many people have been skipping vaccinations, there have been outbreaks of diseases that doctors haven’t seen in decades. The bottom line, Dr. Parikh says: “Vaccines do not cause autism. They also do not make you sick by infecting you with the illness.”

That goes for the flu shot, too. What’s injected is a dead virus, so it’s impossible to contract an illness from the shot. People who experience a reaction are feeling their immune system response kick in. Even vaccines that contain live forms of a virus, such as the MMR (measles, mumps, and rubella) vaccine, use weakened forms of the virus and are safe for most people who don’t have weak immune systems. “Vaccines save lives and prevent illness,” Dr. Parikh says. Read about 10 vaccine myths that you can safely ignore.

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Not true: If you never had a food allergy, you never will

Unfortunately, food allergies are on the rise and becoming more severe, and scientists aren’t sure exactly why. People can develop them at any stage in life, to practically any kind of food, and the effects can range from mild to severe. Although there have been some advances in exposure therapy, which introduces a person to allergens gradually to reduce his or her allergic reaction, Dr. Parikh cautions that this is not something you should ever try on your own. “On the same note, you should not premedicate yourself with a drug such as Benadryl to try to eat a food you are allergic to,” she says. “Each reaction can be different, and an initial mild reaction can become worse on subsequent exposures.” Find out the 14 unbelievable food facts that will change the way you eat.

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Not true: Only kids get asthma

Actually, more American adults (around 20 million) have asthma than do children (about six million), according to the CDC. As with allergies, you can develop asthma as an adult even if you never had it before—and it can be life-threatening if untreated, says Dr. Parikh. You may be surprised to learn these 14 health myths even doctors believe.

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Not true: Eating more protein will give you more energy

Protein fills you up and provides a steady, slow-burning supply of calories; that’s why weight-loss experts recommend it over refined carbohydrates for people looking to ditch a few pounds. But despite what paleo-diet enthusiasts would have you believe, most Americans eat too much animal protein, says Michael Galitzer, MD, coauthor of Outstanding Health: A Longevity Guide for Staying Young, Healthy, and Sexy for the Rest of Your Life. Eating too much meat can contribute to increased acidity in the body and increased inflammation—and that has been linked to many chronic diseases. You only need 50 grams of protein daily, and one 4-ounce burger gets you nearly halfway to that quota. “One of the healthiest things you can do is go vegetarian for dinner while eating protein for breakfast and lunch,” says Dr. Galitzer.

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Not true: Weight loss is a matter of willpower

Willpower might work for a short period of time in dieting, but eventually, almost everyone breaks down. “The human brain is wired to crave high-calorie foods, especially sugar and fat,” says Michael Long, coauthor of The Molecule of More: How a Single Chemical in Your Brain Drives Love, Sex, and Creativity―and Will Determine the Fate of the Human Race. “It’s the chemical dopamine that makes you crave unhealthy food, and it’s very powerful.” He suggests that instead of trying to fight this fact, you should incorporate strategies to avoid hunger and temptation: Stock up on healthy snacks and keep tempting foods out of the house, and go grocery shopping on a full stomach so you’re less likely to make impulse buys.

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Not true: Coffee is dehydrating

Caffeine is known to have a diuretic effect—that means it makes you urinate—but coffee and other caffeinated beverages still count toward your daily fluid intake. “There’s evidence to suggest it can be as hydrating as water,” says Angela Lemond, RD, a national spokesperson for the Academy of Nutrition and Dietetics. Be sure not to follow these 20 worst pieces of health advice on the Internet.

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Not true: Starve a cold, feed a fever

“In general, you don’t want to starve when you’re sick,” says Lemond. “Your body needs energy.” Unless you’re suffering from stomach flu and can’t keep food down, it’s best to try to eat regularly—and definitely stay hydrated, Lemond says: “Being properly hydrated is a balance of fluids and electrolytes. When you’re already low on fluids, only drinking water can be detrimental because you need to replace electrolytes, too.” So make sure you’re eating and drinking once you’re able to. Foods like bone broth and bananas have electrolytes to replace what you’re missing. Check out these 14 facts you’ll wish weren’t true.

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Not true: Eating eggs raises your cholesterol

Yolks used to be a huge no-no, especially when it came to heart health. But research demonstrates that food high in cholesterol won’t raise cholesterol levels in your blood, says Keri Glassman, RD, owner of Nutritious Life. Plus, yolks contain the bulk of an egg’s vitamins, including fat-soluble A, D, E, and K, as well as calcium, iron, and choline. Skip the egg whites only and have one of nature’s most nutritious whole foods: an egg. Read about these 13 downright weird facts about the human body.

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Not true: You don’t really need to floss

More and more research is showing that oral health is closely tied to your general health. In the last few decades, scientists have unearthed evidence that poor oral health and gum disease are linked to systemic diseases such as diabetes, heart disease, and even premature births and low-birth-weight babies, according to dentist Ami Barakat, DMD, author of Perfecting Smiles, Changing Lives: Your Guide to an Exceptional Dental Experience

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Not true: Snoring is normal

Unless you have a cold, you shouldn’t make a lot of noise while sleeping. Snoring isn’t a sign of a deep, restful sleep; it can be a signal that something is wrong in your airways—a potential sleep disorder, says Dr. Barakat. Obstructive sleep apnea has been linked to high blood pressure, type 2 diabetes, and other chronic diseases. It’s best to ask your health-care provider about it. Be sure to check out these 50 myths about the human body that can actually be dangerous.