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Fact or Fiction? The Truth About 40 Popular Medical “Facts”

Knowing which of these statements have been verified by science—and which are totally false—could boost your health.

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True or false: Cold weather makes you sick

FALSE! Germs are the only thing that can make you sick. You can go out in the freezing cold with wet hair, and if there aren’t any germs around, you’ll stay sniffle-free. But there is a correlation: The viruses that cause the common cold thrive in low temperatures.

Signs-You’re-Drinking-Too-Much-Coffeeigorstevanovic/shutterstock

True or false: Not all heart attacks involve chest pain

TRUE! A 2012 study of more than 1.1 million heart attack patients found that 31 percent of men and 42 percent of women didn’t have any chest pain before being hospitalized. The American Heart Association recommends calling 911 for other symptoms, too, including shortness of breath, light-headedness, and pain elsewhere in the upper body. Here are some more silent signs of a heart attack you might be ignoring.

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True or false: Being overweight shortens your life expectancy

FALSE! It’s what researchers call the “obesity paradox,” though the “overweight paradox” would be more accurate. Obesity is linked with a host of health problems, including so-called all-cause mortality, but the evidence isn’t strong for overweightness. A recent review looked at ten studies of more than 190,000 people and found that overweight people had the same longevity as normal-weight adults, though they did have a higher risk of heart disease.

Pieces of crushed ice cubes on black background. Copy space, top view

True or false: You shouldn't ice a burn

TRUE! Most skin damage from a burn comes from the inflammatory response, and ice can damage cells and make it worse. Instead, immerse the burn in cool water for about five minutes. Then wash with mild soap and apply an antibiotic ointment.

Cropped photo of young naked man opening antiperspirant for underarm. He is situating against gray background in studio. Body care and male hygiene concept

True or false: Antiperspirants cause cancer

FALSE! Antiperspirants temporarily keep sweat from escaping, and some scientists have suggested that letting it build up in the ducts could cause tumors. But research hasn’t confirmed that theory and the largest study to date on the subject found no link between cancer and antiperspirants or deodorants. Find out some other things you think cause cancer, but actually don't.

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True or false: CPR doesn't require mouth-to-mouth breathing

TRUE! A 2017 study found that when bystanders gave CPR to people in cardiac arrest, survival rates were higher when they employed uninterrupted chest compressions rather than pausing for rescue breaths.

Range of coconut milk ice cream with chocolate, matcha powder, chocolate chips and vanilla. On a dark background, top view. Gluten free vegetarian dessert Kiian Oksana/Shutterstock

True or false: Eating too much sugar will give you diabetes

FALSE! Sweet foods don’t directly lead to chronically high blood sugar. But they can contribute to obesity, which is a risk factor for diabetes, so keeping a well-balanced diet and limiting treats is still the right idea. Learn the truth about more healthy-eating and food myths you still believe.

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True or false: You shouldn't let someone with a concussion sleep right away

TRUE! For several hours after the initial blow, it’s a good idea to keep the person awake and monitor symptoms. But after that, taking naps and getting plenty of sleep at night are recommended to aid recovery.

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True or false: Tilt your head back if you have a nosebleed

FALSE! Tilting your head back might make you swallow blood, which could irritate the stomach and potentially make you vomit. Instead, tip your head slightly forward and pinch your nose shut for ten minutes.

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True or false: You should eat several small meals throughout the day instead of three big ones

FALSE! While some people who are natural grazers might do better on a small-meal eating plan, others won’t feel satisfied, and the diet will backfire. The goal should be to pay attention to the overall nutrients and calories you’re getting in your meals, not to how you’re spreading them out. Learn the truth about 13 more of the most widespread health debates.

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True or false: Carrots help your eyesight

FALSE! Carrots get their vision-boosting reputation from the chemical that gives them their orange color: beta-carotene. Beta-carotene is converted into vitamin A, which helps your eyes see better in the dark. But the conversion process isn’t very efficient, and once you’ve taken in a certain amount, the body stops converting it. For improved eyesight, eat vegetables high in vitamin A itself, including leafy greens such as kale and spinach.

cup of coffee on a dark backgroundMarie Tsyganova/Shutterstock

True or false: Coffee will dehydrate you

FALSE! The idea that caffeine is a diuretic that leaves your body short of fluids doesn’t hold water. In fact, studies show that coffee and tea drinkers don’t use the bathroom any more than water drinkers. A cup of coffee counts as part of your fluid intake and can actually help you hydrate. Here are 8 more myths (and the truth) about how coffee affects your health.

Close-up Photo Of A Woman Showing Tongue

True or false: A person having a seizure is at risk of swallowing his or her tongue

FALSE! Following conventional wisdom and putting a spoon in the person’s mouth won’t prevent tongue swallowing, but it could harm the teeth or jaws. Instead, turn the person on his or her side to prevent choking on saliva or vomit, and cushion the head with a pillow.

radiator with thermostat temperature controller

True or false: Frostbitten skin shouldn't be warmed up by a heater

TRUE! Frostbite numbs the skin, so it could be burned without your realizing it if it’s next to a radiator, fire, or heating pad. Instead, immerse the area in warm water.

Young Woman Sitting On Sofa Suffering From Stomachache At Home

True or false: Stress will give you an ulcer

FALSE! The two main causes of stomach ulcers are overuse of NSAID painkillers, such as aspirin and ibuprofen, and infection from the bacteria Helicobacter pylori. Stress might make an existing ulcer worse (and having an ulcer might trigger stress), but the current science shows it isn’t a direct cause. There are some other scary ways stress can make you sick, though.

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True or false: You should return to working out after a heart attack

TRUE! “Too often, heart patients use their condition as an excuse to cut back on physical activity when they should be doing the opposite,” says Dr. Salim Virani, chair of the American College of Cardiology’s Prevention of Cardiovascular Disease Council. Hitting the standard 20 to 30 minutes most days can help strengthen your heart. Talk to your doctor about creating a safe routine.

Wooden crate full of fresh eggs on dark background, top view

True or false: Eggs are bad for your heart

FALSE! The old thinking was that cholesterol in food would raise blood cholesterol levels and in turn increase the risk of heart disease. A recent study of more than 400,000 adults found that eating an egg a day increased good cholesterol and cut the risk of cardiovascular death by 18 percent.

Stack of books on dark background

True or false: Reading in dim light will harm your eyes

FALSE! It might tire your eyes in the short term, but there’s no evidence that it will do any lasting damage. When reading, position light to shine directly on the page rather than from over your shoulder to reduce glare. Learn about some common health myths that even doctors believe.

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True or false: Coughing too much can make you throw up

TRUE! Little kids are especially prone to vomiting after coughing fits because their gag reflexes are extra sensitive, but it can also happen to adults. It usually isn’t a big deal, but if you keep puking, see a doctor.

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True or false: Cracking your knuckles will give you arthritis

FALSE! Recent studies haven’t found a link between cracked joints and arthritis. But some studies showed that cracking your knuckles can result in soft-tissue damage (which can cause swelling) and a decrease in handgrip strength. Even though this arthritis myth isn't true, these 13 health "myths" actually turned out to be true.

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True or false: You don't need eight glasses of water every day

TRUE! There’s no scientific evidence that eight is the magic number. You might need more or less than that, depending on factors such as climate and body size. To make sure you are getting enough, just drink water throughout the day.

woman sitting and working in modern office interior

True or false: Sitting up straight can be bad for your back

TRUE! “Hunching can certainly be bad for your back. But the opposite is true, too,” says Dr. Neel Anand, professor of orthopedic surgery and medical director of spine trauma surgery at Cedars-Sinai Spine Center in Los Angeles. “Sitting up straight for too long without a break can also cause strain.” When you’re sitting, keep your lower back supported and your legs uncrossed with your knees at a 90-degree angle, and get up to stretch every half hour or so.

Portrait of back of young black man legs walking barefoot on beach towards water

True or false: People with dark skin can't get skin cancer

FALSE! Dark skin is less likely to burn, but it isn’t immune to harmful UV rays and the damage they cause. People of all skin types need to use sunscreen. Here are more sunburn myths that are damaging your skin.

Lyme disease, Borreliosis or Borrelia, typical lyme rash, spot. A person, leg bitten by a deer tick. Selective focus.AnastasiaKopa/Shutterstock

True or false: If you don't have a bulls-eye rash, you don't have Lyme disease

FALSE! About 20 to 30 percent of people with Lyme disease will never develop that classic rash. Other symptoms to watch for include fever, headache, achy muscles, and swollen lymph nodes and joints.

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True or false: You need less sleep as you get older

FALSE! Older adults often sleep less as a result of chronic conditions that are more common with age as well as the medications used to treat them. But that doesn’t mean they require less sleep. While sleep needs vary from person to person, the U.S. Centers for Disease Control and Prevention recommends most adults get at least seven hours of sleep for optimal health.

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True or false: Bar soap is covered in germs

FALSE! You might transfer germs to the soap while you scrub up, but they won’t last long enough to spread. The most rigorous study on the subject, published in 1965, found that bacteria on a bar of soap die within minutes and are not transmitted to the next person to use the soap. However, these surprising items are probably dirtier than your toilet seat.

Woman preparing fresh cabbage for fermentation on table

True or false: Probiotics can help ease diarrhea

TRUE! While studies haven’t pinned down which “good” bacteria, yeast strains, and doses are most helpful against diarrhea, the research is promising. There’s evidence that probiotics can prevent or reduce diarrhea associated with antibiotics and can ease symptoms in people with irritable bowel syndrome. Other potential benefits include weight loss, cold prevention, and protection from tooth decay, though the studies aren’t conclusive.

Businesswoman with a seasonal winter fever and chill blowing her nose on a white handkerchief as she sits in the shadows in her officestockfour/Shutterstock

True or false: Holding in a sneeze is unhealthy

TRUE! As your body gets ready to sneeze, pressure builds in your lungs. When your body tries to push the air out, it needs somewhere to go—and if you’re pinching your nose and mouth, it could be rerouted to the ears. In rare cases, sending the sneeze in that direction can lead to damage such as ruptured eardrums. While you may have already known about holding in a sneeze, you probably didn't know that these 15 surprising habits are actually unhealthy.

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True or false: You can get the flu more than once a season

TRUE! Every year, there’s more than one flu strain circulating. Getting sick from (or being vaccinated against) one of them won’t protect you or your loved ones from the other strains. That’s why it’s important to take everyday preventive actions during flu season: covering your nose and mouth with a tissue while coughing or sneezing, and washing your hands often with soap and water.

Scan film MRI.

True or false: Depression is incurable

FALSE! “Recovery from depression is not only possible; it’s actually likely when people receive the specific kind and amount of help that they need,” says Mark Henick, a mental health advocate. “When you combine medication with psychological therapy as well as social supports like housing, employment, and engagement, that’s the gold standard for recovery.”

Close up white bottle with medicine pills or tablets on dark background.

True or false: You can stop taking antibiotics when your symptoms go away

FALSE! Even if you’re back in tip-top shape, continue taking your meds as prescribed. The symptoms can fade before the infection clears, meaning you could get sick all over again— and this time it might be more resistant to the antibiotic. So that's absolutely one of the dangerous medication mistakes that could harm your health.

toothbrushesRostislav_Sedlacek/Shutterstock

True or false: You should rinse the toothpaste from your mouth after brushing

FALSE! When you rinse with nonfluoride mouthwash or water, you’re spitting out the fluoride that prevents tooth decay without giving it enough time to work. If you still feel like you need to rinse, studies suggest using a tiny bit of water to swish the toothpaste foam, then spitting it out. This will keep more fluoride on your teeth. Watch out for these other little ways you're brushing your teeth wrong, too.

two cups of coffee on a black background

True or false: Caffeine is good for hearts

TRUE! It might seem as if anything that makes your heart race would put stress on your ticker, but mounting evidence says just the opposite. Studies suggest that drinking three cups of coffee a day is linked to a lower risk of cardiovascular problems. The antioxidants in coffee may play a role, and caffeine might speed up cellular processes that help repair the heart.

Triple dark, milk and white chocolate cookies

True or false: Sugar causes cancer

FALSE! It’s true that cancer cells tend to get their fuel from sugar, but that doesn’t mean that eating less sugar will prevent or slow down cancer. The body makes its own glucose when you eat less sugar, which could negate any cancer-fighting benefit. That said, obesity is a risk factor for certain cancers, so keeping your hands out of the cookie jar can still have an indirect anticancer effect. Here are some more rampant cancer myths you need to stop believing.

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True or false: Running is bad for your knees

FALSE! Research has found that recreational runners are not at increased risk of having symptoms of knee arthritis or other orthopedic problems. In fact, running may strengthen muscles that stabilize the knee, which may help prevent injuries and arthritis.

Wine pouring from bottle on dark background

True or false: Alcohol warms you up when it's cold outside

FALSE! You might feel warmer and your face may start to flush as you sip that hot toddy, because alcohol causes your blood vessels to dilate, moving warm blood closer to the skin. But this perception of warmth also causes you to stop shivering, which actually brings your core temperature down.

medical syringes on a dark background

True or false: Vaccines can cause autism

FALSE! Some people have raised concerns that substances used in trace amounts in certain vaccines—including formaldehyde, aluminum salts, and thimerosal, a mercury-based preservative—could cause autism. But none of these substances has been shown to cause harm in the small doses used in vaccines. Nor is there any evidence that multiple or combination vaccinations, such as those recommended for children, can weaken the immune system and trigger autism, as some people fear. It's just one of several myths about vaccines that you can safely ignore.

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True or false: Women should be as worried about colorectal cancer as men are

TRUE! Colorectal cancer is the third most common type of cancer among men but the second most common for women. Men do have a slightly higher risk overall: About one in 22 men will develop colorectal cancer, compared with one in 24 women.

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True or false: Sitting too close to the TV damages your eyes

FALSE! Until the late 1960s, the amount of radiation coming from TVs wasn’t well regulated, so some people worried that sitting too close could cause health problems. Modern TVs don’t pose that risk. Staring at anything for a long time can make the eyes feel tired, but it won’t do permanent damage.

Medicine and health care concept Doctor giving patient vaccine insulin or vaccination

True or false: The flu shot might give you the flu

FALSE! Vaccines do contain inactivated viruses in order to produce an immune response. You might experience minor side effects after your shot, such as aches or a low-grade fever, but unless you have a compromised immune system, it’s unlikely that you’ll get the full-blown flu. Read on to learn more health myths like this that make doctors cringe.

Originally Published in Reader's Digest International Edition