Cold Weather Won't Make You Sick

Myth
Most of your body heat is lost through your head.

Fact
Untrue. This myth likely originated from a 50-year-old military study; subjects enduring extreme cold lost the most heat from their heads. But the head was the only exposed body part, says Rachel Vreeman, M.D., coauthor of Don't Swallow Your Gum!: Myths, Half-Truths, and Outright Lies About Your Body and Health. The real deal? "You lose heat from whatever is uncovered," Vreeman says. "There is nothing special about the head."

Myth
Taking vitamin C and zinc will help prevent or shorten a cold.

Fact
Taking vitamin C daily won't prevent illness, and if you consume it after feeling sick, it won't ease symptoms, studies show. As for zinc, three of four well-designed studies found it ineffective, while a fourth found that zinc nasal gel helped relieve symptoms. But in June the FDA recalled some zinc nasal products, since they're linked to a loss of sense of smell. Bottom line: There's no need for extra C, and zinc may actually harm you.

Myth
You should drink at least eight cups of water per day.

Fact
There's no medical reason to follow this advice. In 1945 the Food and Nutrition Board of the National Research Council recommended that adults take in 2.5 liters of water per day (about 84.5 ounces), noting that most water comes from food. Many adherents, however, ignored the last part of that statement. Drink up if you'd like, but studies suggest that most people already get enough H2O from what they eat and drink: the average person takes in about 75 ounces of water daily, according to Department of Agriculture surveys.

Myth
Illnesses come from cold or wet weather.

Fact
Colds and flus come from viruses, not the climate, explains Aaron Carroll, M.D., Vreeman's co-author. But because some viruses are more common in winter, more people may get sick then. Plus, chilly or rainy weather often results in more people staying inside—and then sharing their icky infections.

Myth
You're really using only 10 percent of your brain.

Fact
Brainiacs rejoice—now you can sound really smart when you refute this misconception. Images from numerous studies show that no area of the brain is completely shut down, and each region of the brain has a function. "Neurons everywhere in the brain are pretty well continuously active," adds Michael Rugg, Ph.D., director of the Center for the Neurobiology of Learning and Memory at the University of California, Irvine.