Misconception: Juice cleansing can remove toxins from your system.

Actually: To say that drinking juice detoxifies the body isn’t quite the same as claiming leeches suck out poisons, but it’s fairly close.

The practice of cleansing has become as ubiquitous as the use of hand sanitizer. Celebrities do it. Spas offer it. Fancy food stores sell pricey bottles of juice to accomplish it, and a $700 juicer will soon facilitate the process for those who are not satisfied with the current D.I.Y. options. But what is it that everybody is trying to remove from their bodies? Is there any science behind it?

“People are interested in this so-called detoxification, but when I ask them what they are trying to get rid of, they aren’t really sure,” said Dr. James H. Grendell, the chief of the division of gastroenterology, hepatology and nutrition at Winthrop-University Hospital in Mineola, N.Y. “I’ve yet to find someone who has specified a toxin they were hoping to be spared.”

Toxins exist. Doctors typically define them as something that enters the body that has a damaging effect on its own — like pesticides, lead or antifreeze — or in large quantities, like alcohol or medications such as acetaminophen, the active ingredient in Tylenol.