Chelation therapy has long been scorned by many in the medical community as quackery. But after a major study seemed to question that hardline view, the alternative health treatment is once again going under the microscope.

Chelation therapy is not new; Health Canada has long approved its use to treat heavy-metal poisoning, such as lead, mercury and arsenic poisoning.

But the therapy has also been embraced by alternative medicine practitioners, who claim chelation can help "detoxify" the body, and relieve myriad illnesses and conditions.

The therapy involved delivering a solution called disodium EDTA, or ethylene diamine tetraacetic acid, which binds to heavy metals in the blood and eliminates the metals through the urine.

Most cardiologists, such as Dr. Gervaio Lamas, are told that chelation is not helpful for heart disease.

"I'm a conventionally trained cardiologist, and we were all taught that chelation was quackery, dangerous, expensive, and bunk," he told CTV News from Miami.

But Dr. Lamas says when a patient asked him about it back in the late 1990s, he began to look into it and he realized the therapy hadn't been fully and rigorously studied.

So he launched a multi-year study on chelation, assuming he'd find enough evidence in a clinical trial to finally discredit the therapy.

His team tested chelation on 1,700 Canadian and American patients over the age of 50 who had had a recent heart attack. Almost one-third of the group also had diabetes.

The patients came in for weekly or bi-weekly chelation infusions over several months, with half the group receiving EDTA and the other half receiving a simple vitamin and mineral infusion. The study was double-blinded so that neither the researchers nor the patients knew who was getting what.

When the trial ended after seven years, Dr. Lamas was stunned by the results: not only was chelation safe, it appeared somewhat effective for heart disease. The chelation group had an 18 per cent lower risk of heart attacks, as well as reduced risks for stroke, hospitalization for angina, or the need for bypass surgery.

"I was the most shocked member of the team when the study came out positive," Dr. Lamas recalls.

"…We looked at the results and my first question to the statisticians was, did you get the groups right? Did you confuse the chelation with the placebo arm?"

The reduction in heart attacks was modest, but was most pronounced in patients with diabetes, who saw a 41 per cent reduction in recurrent heart events, and a 43 per cent reduction in deaths.

Dr. Lamas had the full results of his study published in JAMA, the Journal of the American Medical Association.

It was met with plenty of skepticism and criticism. Many criticized the trial's methodology while others, including the American Heart association, said the study had not offered enough evidence to support the use of chelation in heart disease. 

So now Lamas is preparing to do the study again, this time focusing only on patients with diabetes. The new study, called TACT 2 (Trial to Assess Chelation Therapy),  is recruiting another 1,400 patients across Canada and the U.S. to assess chelation's benefits, backed with US$37 million from the U.S. National Institutes of Health.

Dr. Michael Farkouh, a cardiologist at the Peter Munk Cardiac Centre in Toronto, is heading the Canadian arm of the study. He says many patients with diabetes who had had a major heart event like stroke or a heart attack remain at high risk of another heart event -- even if they follow their doctors' advice and take cholesterol-lowering medication and other drugs, or undergo bypass surgery.

Dr. Farkouh says he's interested in this trial because it proposes a whole new approach.

"We have gone to a new paradigm and to a new theory and instituted something that is out-of-the-box thinking, which is something I think medicine needs now," he said. "We have gone down traditional pathways and now and we are going down a different pathway."

Dr. Diana Visentin agrees. She is an internal medicine specialist in Barrie, Ont., who was also once among the skeptics of chelation. But faced with a rising tide of Canadians with Type 2 diabetes, and complications like heart disease, she trained for 2 years in order to join the TACT 2 -- and has become one of the first clinics offering the therapy -- as part of the research study.

"Diabetes is an epidemic. The prevalence is increasing, the tsunami of complications is still to come…and if we can  slow that tide, it will be a benefit to all of us," she said.

Patients undergo chelation therapy, or IV with a placebo solution, for 3 hours at a time, for 40 visits. Researchers hope for results in about four years. 

With a report from CTV medical specialist Avis Favaro and producer Elizabeth St. Philip