Debunking common health myths

Have you ever hesitated before diving into a pool, trying to remember if it's been at least 30 minutes since you ate? Or stayed far away from someone with poison ivy for fear of contagion? Health myths buzz around summer pastimes, and people have a hard time letting go of word-of-mouth wisdom, even when faced with good evidence to the contrary.

"Myths stick with us because they make sense to us, on some level," says Indianapolis pediatrician Rachel C. Vreeman. "When you've heard them from your grandmother and mother and important adults in your life, you believe those things."

Here are some debunked myths:

MYTH: SWALLOWING

WATERMELON SEEDS

IS BAD FOR YOU

Swallowing a few watermelon seeds won't do any harm, nutritionist Rebecca Scritchfield says. Our bodies try to digest them but can't, so the seeds pass directly through our system.

If someone was to chew up and eat every seed in a watermelon, the only danger would be overdoing fat and calories for the day, Scritchfield says. One cup of seeds contains 602 calories, 31 grams of protein and 51 grams of fat, a day's worth for most people.

Small children might imagine that watermelon seeds could sprout in their stomachs (or be tricked into thinking this). There have not been any reports of that happening -- and it's unlikely, given how strong digestive acids are -- but in 2010, a pea seed did sprout in a man's lung: A seed he had aspirated grew a half-inch-long sprout and had to be surgically removed at Cape Cod Hospital in Massachusetts.

MYTH: YOU CAN CATCH POISON IVY FROM

SOMEONE WHO HAS IT

No matter how icky and oozy a poison-ivy rash looks, the rash itself is not contagious, Vreeman says. It's the oil from the poison ivy plant that is contagious, not the reaction to it that is the blistery rash you see on someone's skin.

Poison ivy causes a delayed response; the rash doesn't appear for 24 to 72 hours after contact with the plant oils, which are found on the leaves and on the stems, and it can spread for days, even without additional contact with the oil, depending on individual reactions and sensitivities, according to the American Academy of Dermatology. By the time the rash is in full force, it's unlikely the person would still have the oil on his or her skin. The blisters cannot spread the rash to other people, nor to other parts of the infected person's body. The oils can stick around on clothes and shoes, though, so be sure to wash everything that might have brushed against the ivy.

"Leaves of three, let them be," as they say.

MYTH: DON'T SWIM FOR

30 MINUTES AFTER EATING.

If you have a big meal and then go for a swim, the worst thing that could happen is you'd feel uncomfortable or get a cramp, not drown, according to nutritionist Scritchfield. (There are no documented cases of drowning or near drowning attributed to eating, according to Vreeman.)