Dr. Oz and Oprah hold a tapeworm.

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If there's one thing Dr. Oz likes as much as talking about poop, it's props! This time he's brought along a real doozy.

"Wormzilla" is a tapeworm—a type of parasite that can grow up to 30 feet long.

Tapeworms attach their suckers to the hosts' stomach and siphon calories. The only thing their long bodies do is use up the calories they steal. "In fact, one of the things that folks who have tapeworms complain of is weight loss," Dr. Oz says.

The most common reason people get tapeworms is from eating raw meat. "Which," Dr. Oz says, "is the main reason humans began to cook their food."

Dr. Oz says other parasites may have played huge roles in human history. Some people think that hookworm may have cost the South the Civil War. People who didn't wear shoes were particularly vulnerable to contracting a hookworm infection, sometimes called "Southern anemia," which left the host weakened. Because many Southerners who didn't wear shoes as children developed "Southern anemia," they grew up to be poor choices to be Confederate soldiers. Meanwhile many Northern children wore leather shoes growing up and never contracted hookworm and remained healthy.

"You know how the hookworm got to the South? In the slave ships," Dr. Oz says. "It goes full circle."
As a reminder, always consult your doctor for medical advice and treatment before starting any program.