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Colonic irrigation, a treatment widely offered in health spas as a natural way to lose weight and detox the body, has no health benefits and can cause dangerous side effects, U.S. scientists said Monday.

The procedure, which involves flushing the colon with water through a tube inserted in the rectum, can lead to nausea, cramping, bloating and in some extreme cases, renal failure and even death, according to a study by Georgetown University.

Lead author Dr. Ranit Mishori, a physician at the university, said, "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."

She added, "Colon cleansing products in the form of laxatives, teas, powders and capsules ... tout benefits that don't exist."

The report, which looked at 20 previous studies on colonic irrigation published in medical literature over the past decade, said that as well as no evidence of any benefits, the spas and clinics administering the treatment have no significant medical training.

Even organizations such as the National Board for Colon Hydrotherapy do not require practitioners to have much more than a high school diploma, the researchers wrote in the Journal of Family Practice.

Mishori recommended natural ways to improve well-being, advising health-conscious people to "eat a balanced diet, exercise regularly, get six to eight hours of sleep and see a doctor regularly."

Colonic irrigation can be traced back to the ancient Egyptians but was discredited by the American Medical Association in the early 20th century.

However, the treatment made a comeback in recent years and has been linked to celebrities including Jennifer Aniston and Courtney Love and Diana, Princess of Wales.