That’s the focus of a new book, “Don’t Swallow Your Gum! Myths, Half-Truths and Outright Lies About Your Body and Health,” by Dr Aaron E Carroll and Dr Rachel C Vreeman.

Carroll and Vreeman, both from the Indiana University School of Medicine, have written a lot about medical myths and misunderstandings.

Here are a few medical myths that may

surprise you:

1. Cold weather makes you sick

In studies of cold transmission, people who are chilled are no more likely to get sick than those who were not. It may be that cold weather keeps people indoors, where germs are more likely to catch up with you.

2. Green mucus indicates a sinus infection

The importance of mucus colour is a medical myth even doctors believe. “There is no evidence… that antibiotics shorten the duration of an illness when green snot is a symptom,” the authors write.

3. You lose most of your body heat through your head

There is nothing special about the head and heat loss. You will lose heat through any uncovered body part.

4. Milk makes you phlegmy

In a study of 330 patients, nearly two out of three believed milk increases phlegm production. But it’s not true. In one experiment, volunteers were infected with the cold virus, and some of them drank a lot of milk as well. The weight of the nasal secretions did not increase in those who drank more milk, nor was it associated with cough or congestion.

5. Sugar makes kids hyper

Numerous studies show sugar doesn’t affect behavior, but most parents don’t believe this. In one study, parents were told their kids had sugar and they were more likely to report problem behaviour — but in reality, the kids had consumed a sugar-free drink.

6. Cracking your knuckles will cause arthritis

Knuckle-crackers are no more likely to have arthritis than those who don’t make annoying popping sounds with their fingers.

7. Birth control pills don’t work as well with antibiotics

A review of the literature concluded that common antibiotics do not affect birth control pills. “It is much more important to take your birth control pill every day at the same time than to spend time worrying about your antibiotics,” the authors write.

8. Singles have better sex lives than married people

You may think your bachelor friends are having all the fun, but single people also go through a lot of dry spells when they aren’t dating anyone. The result — married people typically have more sex in a given year than single people.

9. It’s okay to double dip in the chip dip

In one study, scientists took a bite of cracker and then dipped it into salsa, cheese dip, chocolate syrup and water. They did the same test with

a fresh, unbitten cracker. Then they measured bacteria in the dips and the volunteers’ mouths. On average, three to six double dips transferred about 10,000 bacteria from the eater’s mouth to the dip. And each cracker picked up between one and two grams of dip. Salsa picked up the most germs from double dipping.

10. You should poop at least once a day A half-truth, say the authors.

Regular bowel movements prevent discomfort and constipation, but a perfectly healthy person may not move their bowels every day. Constipation is defined as having fewer than three stools per week.

11. Food quickly picked up from the floor is safe to eat

Scientists have put the commonly-cited five-second rule to the test. They found that food that comes into contact with a tile or wood floor does pick up large amounts of bacteria. Food doesn’t pick up many germs when it hits the carpet, but it does pick up carpet fuzz.

The New York Times