9 Biggest Health Myths — Debunked

(This article previously appeared on Grandparents.com.)

We've all heard these "wisdoms," from washing your hands with warm water to not sitting on a public toilet seat. But it turns out, they're all false.

Why it's false: We've all learned that washing your hands in warm water is best for fighting germs, and taught it to our own kids, but studies now show it's not really true. "While it is true that heat kills bacteria, the water would have to be 212 degrees Fahrenheit — the level of boiling water — in order to kill germs," says Dr. Donnica Moore, founder and president of DrDonnica.com, a popular women’s health website.

(MORE: 10 Myths About Aging, Debunked)
 
The hot water people generally use for hand washing is 104 to 110 degrees Fahrenheit. "There was a study done that looked also at whether cold water, around 40 degrees Fahrenheit, would decrease bacteria and the answer was 'yes'," Moore says. "So long as hands are rubbed and scrubbed, and they are dried with a clean towel, the temperature of the water doesn't matter."
 
Time spent washing matters more for killing germs, according to the Centers for Disease Control and the Mayo Clinic, both of which recommend 20 seconds of scrubbing.
 
One more thing to note: "A study out of Vanderbilt University found that Americans wash their hands in warm water 8 billion times a year, which produces the same harmful levels of CO2 as 1.25 million cars," Moore says. "The point is, wash hands in cold water and also save energy."
 

Why it's false: "It might feel intuitively right to tilt your head back to stop a nosebleed, but actually you should sit up straight and tilt your head slightly forward," says clinical exercise physiologist Bill Sukala, who is based in Sydney, Australia.
 
Medical guidelines from the American Academy of Family Physicians support Sukala's advice: "Tilting your head forward will prevent blood from running down the back of your throat, which can cause choking, and prevent it from going into your stomach, which might cause stomach upset."
 
Instead of pinching the bridge of the nose, Sukala suggests pinching a bit lower across the soft tissue. "Using ice will help to shrink blood vessels and, along with light pressure, should help minimize the bleeding." If the bleeding persists for more than 20 minutes, you should seek medical attention.

(MORE: Scary Symptoms That are (Usually) Harmless)
 

Why it's false: "The truth is that total calorie intake determines body fatness, not the proportion of dietary fat or carbohydrates," says nutrition and fitness expert Dr. Pamela Peeke, author of The New York Times bestseller The Hunger Fix. "This myth came into being as a pendulum swing from the 'fat will make you fat' trend to the 'carbs will pack on the weight' trend of the Atkins diet era."
 
Research has shown that people gain weight because they consume too many calories and most probably are not getting enough exercise either, Peeke says.
 
She also notes that more calories are packed into a gram of fat than a carb. "A carb equals four calories per gram while fat equals nine calories per gram," she says. Translated: Carbs aren't bad. You just need to watch the quality, as well as the quantity, of everything you eat. And remember, serving sizes count.

(MORE: The Trouble With (Some) Carbs)
 

Why it's false: Sorry to say, there's no such thing as blue blood. "As much as people believe that blood is blue when they look at their veins, it's an optical illusion," Moore says. "It's similar to the blue-black dress vs. white-gold dress photo that recently went viral online. Blood appears blue because light is diffused by the skin."
 
As far as blood being blue until it comes into contact with air, think about when you get blood drawn, says Moore. "The technician uses a vacuum-sealed tube so no air is inside. When blood is drawn it doesn't come out blue, it comes out a dark maroon red color." Mystery solved. 
 

Why it's false: "The truth is that all taste sensations come from all parts of the tongue," Peeke says. "The source of this myth came from a paper written by Harvard psychologist Edwin Boring in which he interpreted a 1901 German study that suggested that each part of the tongue tastes exactly one basic taste. From that, a 'tongue map' was created noting sections of the tongue correlated with specific tastes."
 
All of this has been debunked with research. In a 2006 study, according to The New York Times, a team of scientists reported that "receptors for the basic tastes are found in distinct cells that are not localized, but are spread throughout the tongue.” What does that mean? Specific tastes are tasted all over, not just in one place.
 

Why it's false: "There's a time-honored myth that people get STDs and other viruses from toilet seats," Moore says. "But the only way to get an STD on a toilet seat is having sex with someone who has an STD while sitting on a toilet seat." The truth is, she says, is thath most bad germs that cause diseases can only live for a very short time on the surface of a toilet seat. "It is extremely, extremely unlikely to get sick this way."
 
The bigger problem with public bathrooms: Only 67 percent of people wash their hands after using the toilet. "There is a much bigger risk when people go from wiping themselves to using handles of the sink or door," she says. In essence, "you're more at risk for getting an illness from not washing your own hands than you are for getting an infection from someone else who used a toilet seat," she says.
 
Moore's advice: Take some toilet paper and wipe the seat beforehand, then sit or don't sit, it's your choice. And use your foot to flush since the toilet handle is where germs congregate.
 

Why it's false: "For many years, coaches and athletes alike stuck by the mantra that stretching prevents injuries," Sukala says. "Anecdotally, this might seem to be the case, but further scientific evaluation of this claim suggests that there is no difference in injury rates between those who stretch and those who don't."
 
So does that mean you shouldn't stretch? "The confusing thing about science is that for all the questions it answers, a number of other questions pop up in their place: What type of stretching? Is it to help an injury? How long are stretches held?" Sukala says. "Certain types of stretching may have no effect on particular types of injuries, but may very well help in others."
 
The bottom line: Stretching probably isn't going to hurt you, so if you like your routine and it makes you feel great, then keep on doing it. 
 

Why it's false: "We've all seen retired athletes whose bodies have gone to pot. While it might seem like their former muscles have 'turned to fat,' this is not true," says Sukala.
 
Nor is it true that fat turns into muscle if you exercise. “Fat and muscle are two different metabolic tissues, and one does not convert into the other," he says. 
 
What does happen is this: As you start eating healthfully and exercising, the fat gradually burns off and goes away, and you start to build muscle. It's two totally separate processes. 
 

Why it's false: "Adelle Davis, a popular nutritionist in the '60s and '70s, started this when she said to 'eat breakfast like a king, lunch like a queen and dinner like a pauper,'" Peeke says. "But weight gain caused by eating late is a complex issue that's not wholly false or true."
 
Mouse studies first noted that those consuming food in the evening gained twice the amount of weight as those that ate the same number of calories during the day. Other studies have noted no difference in weight changes regardless of time of day the food is consumed.
 
"Science and reality are conflicted here. Although some science says that there is no difference, in reality, there are many factors that make late-night eating a real problem," Peeke says. "The catch is that when people eat later, they often tend to eat more mindlessly as they’re tired and not vigilant." Eating later can affect appetite in the morning, so that you don’t feel like eating. "This dysregulates ghrelin, the hunger hormone, and leptin, the appetite hormone," she says. "When they are not functioning optimally, appetite is off and people tend to overeat." 
 
Finally, science has shown that people who tend to be larks, or early-morning types, have a much easier time controlling their weight, as opposed to owls, who are up all night and have a greater propensity to raid the fridge. Lesson learned.