Gwyneth Paltrow's "Goop" teamed up with the Clean Program to create a colon cleanse. (ChinaFotoPress/Getty Images)

Gwyneth Paltrow's lifestyle blog has its own  colon cleanse for "Goop" groupies.

The Goop Cleanse, co-designed by Goop and  Clean Program creator Dr. Alejandro Junger, contains protein, fiber, digestive enzyme and probiotic supplements that "help give your digestive system a break and also improve energy levels by bringing in high-quality vitamins and nutrients," according to Junger. "Best of all, because you'll be eating during this program, you won't be left feeling hungry or tired which is typical of most cleanses."

For 21 days, Goop cleansers will start the morning with a shake, eat lunch from an elimination diet menu boasting roasted squash over millet and "salmon salade nicoise," and have another shake for dinner. Dairy, eggs, wheat and coffee are among 77 forbidden foods. The goal is to still consume at least 1,200 calories a day, which is low compared to the 1,600-to-2,000 recommended for women. To get the calorie count up, the Goop Cleanse manual recommends adding avocado or coconut oil to daily shakes.

"I've used Clean in the past with great results, losing a few pounds and kickstarting a healthier and more energetic New Year," Paltrow  wrote on Goop. The cleanse is designed for use every eight-to-12 months and costs $425.

Colon cleansing has been around for centuries. It can be accomplished in a number of ways, from supplements to colon hydrotherapy - an enema-like procedure that uses water to flush out the large intestine. Proponents claim it purifies the body by removing toxins that build up in the digestive tract, but some experts say the practice can do more harm than good.

"Despite colon cleansing's long history and current popularity, the literature does not support its purported benefits," Dr. Ranit Mishori of Georgetown University School of Medicine wrote in an  August 2011 report published in the Journal of Family Practice. In fact, colon cleansing can cause painful side effects ranging from cramping to kidney failure, according to the report.

"The body is designed to detoxify itself," Mishori told ABC News in August, adding there are safer ways to help it along, including diet and exercise.

But thanks to celebrity devotees like Paltrow, Beyonce and the Kardashians, more people are asking their doctors about colon cleansing.

"I keep it simple," Dr. Roshini Rajapaksa, assistant professor of medicine at NYU Langone Medical Center and author of " What the Yuck?! The Freaky and Fabulous Truth About Your Body" told ABC News. "I say, it can't help you, but it could hurt you, so don't do it."

Rajapaksa said supplement-based cleanses are generally safer than procedures like colon hydrotherapy, but added there's no upside to either and potential downsides to both.

"You're not necessarily getting all the nutrients you need," she said of supplement-based cleanses that exclude several foods, like the Goop Cleanse. "There are definitely natural things people can do if they're feeling a bit backed up, like upping fiber intake with fruits and vegetables and drinking a lot of water."

Dhru Purohit, founding partner and CEO of the Clean Program agreed most cleanses are "garbage" akin to crash diets. But the Goop Cleanse, he insists, is different.

"We developed this program to be kind of like the anti-cleanse," he said. "It's extremely different from what most people go through on a cleanse."

Purohit said the goal of the Goop Cleanse is to inspire healthy, long term lifestyle changes.

"To us, cleansing without lifestyle change is nothing," he said, adding that the cleanse encourages people to adopt a diet high in fruits and vegetables and low in processed foods beyond its 21-day course. And if it doesn't? "You're eating better for a period of time and you're taking some supplements; what's so crazy about that?"

Purohit said the low-calorie cleanse diet helps "reset" the body.

"You're not living on a cleanse for the rest of your life," he said. "Our bodies are just overloaded with too much coffee, too much alcohol, too much processed food. Almost everybody can benefit from making some dietary improvements."

But Purohit said the cleanse isn't for everyone.

"We're big on education: Talk to your doctor. And if a cleanse isn't right for you right now, you'll for sure benefit from an elimination diet."