1. CLAIM: You need 10,000 steps a day to boost your longevity.

What science shows: The latest research shows that as few as 6,000 steps a day can do it. One 2022 study found that adults 60 and older who clocked 6,000 to 8,000 steps daily had a 50 to 60 percent lower chance of early death.

2. CLAIM: Running will damage your knees.

What science shows: Studies in recent years reveal that running does not raise your risk of knee problems. In fact, pounding the pavement seems to protect your joints. One large study found that runners were half as likely to develop knee osteoarthritis compared with non-runners. Runners typically have stronger quadriceps muscles, which helps to protect the joint, explains Grace Lo, a researcher at Baylor University College of Medicine.

3. CLAIM: You need to drink eight glasses of water a day.

What science shows: Many people aim for the often recommended eight glasses of water a day, but there’s no science behind that number, says Karyn Eilber, a professor of urology and obstetrics and gynecology at Cedars-Sinai Medical Center. Urine color is a good indicator; it should be light to medium yellow.

4. CLAIM: Everyone should take a daily multivitamin.

What science shows: A 2022 review of 84 studies by the U.S. Preventive Services Task Force found no convincing evidence that multivitamins have any benefit for nonpregnant adults. “You’ll get much more bang for your buck if you eat a healthful diet with plenty of fruits and different vegetables,” says Jeffrey A. Linder, chief of general internal medicine at Northwestern University Feinberg School of Medicine.

5. CLAIM: Rest when you have back pain.

What science shows: While it’s fine to rest for a day or two after a back flare-up, studies over three decades show that you will recover faster if you remain active, says James Powers, an internal medicine geriatric physician at Vanderbilt University Medical Center. Prolonged bed rest makes most types of back pain worse. “The more you don’t use your muscles, the stiffer you will get,” he says.

6. CLAIM: CPR requires mouth-to-mouth contact.

What science shows: Studies of adults who experienced cardiac arrest outside a hospital found that cardiopulmonary resuscitation involving only chest compressions given by rescuers who weren’t medical professionals is just as effective as—if not more effective than—CPR administered with rescue breathing, says Ahamed Idris, an emergency medicine physician.

7. CLAIM: Green or yellow mucus means you need an antibiotic.

What science shows: Green or yellow mucus is a sign your body is fighting off an infection, says William Schaffner, an infectious disease expert at the Vanderbilt University School of Medicine. Most respiratory infections are caused by viruses, not bacteria, he notes—and antibiotics don’t work on viruses.

8. CLAIM: The flu shot can give you the flu.

What science shows: This exasperates doctors because it’s biologically impossible, Schaffner says. “The vaccine is made from [inactive] pieces of the virus.” People who say they got the flu after the shot may have picked up a different type of respiratory infection. It takes about two weeks for the shot to be fully effective.

9. CLAIM: You’ll get sick if you go out with wet hair or no coat.

What science shows: Going out in winter temperatures without a coat or with wet hair may make you shiver, but that alone won’t make you sick. “Colds are caused by viruses, not by cold temperatures,” Schaffner says. A few studies have found that cold temperatures may suppress the immune response, so if you do encounter a virus, you may be more likely to get sick.

10. CLAIM: Avoid dairy if you have a cold.

What science shows: The idea that milk increases mucus is centuries old, but most research indicates that dairy products do not increase the production of phlegm. In one study published in the American Review of Respiratory Disease, people with the common cold showed no increased phlegm or congestion when they drank milk. Another study found no difference in mucus production between milk and soy milk.

11. CLAIM: Avoid exercise if you’re unwell.

What science shows: Studies have found that mild to moderate exercise when you have an upper respiratory infection may help you feel better faster. Lying in bed can weaken your muscles and predispose you to pneumonia, Schaffner says. Light exercise prompts you to breathe deeply and cough, which “gets things up.”

12. CLAIM: Coffee dehydrates you.

What science shows: Caffeine is a mild diuretic, meaning it can stimulate your body to produce extra urine. However, research shows the liquid in coffee counteracts any dehydration effects. One study published in the American Journal of Clinical Nutrition found that people urinate the same amount whether they drink coffee, soda, tea, a sports drink or water.

13. CLAIM: If it’s an actual heart attack, you will have chest pain.

What science shows: About 42 percent of women and 31 percent of men don’t have chest pain during a heart attack, according to a study published in JAMA. Other symptoms include shortness of breath, light-headedness, nausea and pain or discomfort in the back, neck, jaw, or one or both arms.

14. CLAIM: Cranberry juice cures urinary tract infections.

What science shows: Chugging cranberry juice won’t help if you have a bladder infection, says Pamela Levin, associate professor of urogynecology at the University of Pennsylvania. “If you have symptoms such as burning while urinating, you typically need antibiotics and care from your doctor,” she says. “[Cranberries] are linked to preventing, not treating, infections.”

15. CLAIM: Air hand dryers are more hygienic than paper towels.

What science shows: They may save trees, but air hand dryers in public restrooms don’t remove germs as well as paper towels, according to research. Even worse, they may spread germs around. One study published in the Journal of Hospital Infection found that airborne bacteria counts were 27 times higher when jet air dryers were used.

16. CLAIM: You can lose weight and toxins with a juice cleanse.

What science shows: Juice cleanses are touted as healthy and slimming. But research shows no proof of benefit, and some cleanses may put your health at risk. In fact, one review study found no evidence that detox diets work to eliminate toxins.