Beyonce, Halle Berry and Jennifer Aniston are said to have tried them. Princess Diana was said to have loved them. Many celebrities have touted the purifying effects of colon cleanses, or colonics. But doctors are warning that procedure can actually be dangerous.

Colonics are often promoted as a natural way to "clean out" toxins and "reset" the digestive system. The treatments can be done either at a spa or at home. They usually involve pumping water, with or without added substance such as herbs, through the rectum via a tube. Waste is then expelled through another tube.

Unlike enemas, in which a small amount of fluid is used, colon cleansing introduces up to 60 litres of fluid into the rectum.

Dr. Ranit Mishori, a family medicine doctor at Georgetown University School of Medicine led a team who reviewed all studies done in the last 10 years on colon cleanses, to evaluate their benefits and risks. They also looked at studies of colon cleansing oral laxatives, teas, and other products taken by mouth.

The reports found little evidence of benefits from any of the products. But the studies did note a number of possible side effects following the use of colon cleansing products, including cramping, bloating, nausea, vomiting. Some also experienced electrolyte imbalance and kidney failure.

In the report, Mishori describes two patients she cared for who had colon cleansing. One experienced cramps, diarrhea, and vomiting. The other was hospitalized for dehydration and inflamed pancreas.

"There can be serious consequences for those who engage in colon cleansing whether they have the procedure done at a spa or perform it at home," Mishori said in a Georgetown University Medical Center news release.

She added that colon cleansing products in the form of teas, powders and capsules with names such as Nature's Bounty Colon Cleaner "tout benefits that don't exist."

Mishori says there are much better ways to enhance well-being: "Eat a balanced diet, exercise regularly, get six to eight hours of sleep and see a doctor regularly."

Mishori's study, which is published in The Journal of Family Practice, advises doctors to tell their patients that colon cleansing has no proven benefits and many adverse effects.

"Ask patients with otherwise unexplained nausea, vomiting or diarrhea if they engage in colon cleansing," the study authors advise.