8 Health Lies Trainers Tell

"Heat and vigorous exercise help you sweat out toxins."

You aren't likely to purify your body of much of anything by sweating, whether in a hot yoga class or sizzling sauna, because all that's in perspiration is water, salt, and a smattering of electrolytes, according to Rachel Vreeman, MD, author of Don't Cross Your Eyes...They'll Get Stuck That Way! "Sweat glands sit in the skin and aren't connected to other systems in the body, so it makes no sense that they would eliminate waste," she says. "The only role of perspiration is to keep us cool." The body does a pretty good job of getting rid of what it doesn't need, largely through the liver, kidneys, and digestive tract. There's nothing special you have to do to help, other than eat well, stay hydrated, and keep fit so those organs can function properly.