The National Heart, Lung, and Blood Institute (NHBLI) appreciates the opportunity to
present our views on EDTA (ethylenediaminetetraacetic acid) chelation therapy in this
statement for the record.
Chelation is a chemical term named from the Greek word chele, meaning "claw" or "claw-like."
In chelation therapy, an organic chemical bonds with metals in the bloodstream and digs
them out of the system. This therapy is standard treatment for heavy metal poisoning, such
as lead poisoning, and the management of iron overload following repeated blood
transfusions.
During the 1950s, it was observed that a patient who was receiving chelation therapy
for lead poisoning coincidentally experienced relief of angina symptoms. Since that time,
many patients have sought and received chelation therapy for atherosclerosis, a "hardening of the arteries"that leads to heart disease and stroke. One theory
behind using chelation to treat this disease is that it may remove calcium, which is
present in some atherosclerotic lesions, and therefore decrease the obstruction in the
arteries. The patient receives repeated intravenous infusions of the drug EDTA that, some
believe, grasps the calcium and pulls it from the area of obstruction.
However, others believe that when EDTA is administered intravenously, it encounters and
binds with calcium circulating in the blood, and not with any calcium that may exist in
the atherosclerotic lesions. According to this view chelation therapy not only may be
ineffective in reversing atherosclerosis, but also may expose the patient to risk by
depleting the body of calcium and other essential nutrients.
There is, in fact, no sound evidence that EDTA chelation therapy is effective or has
clinical benefit for atherosclerosis. For nearly three decades, the NHLBI has carefully
followed the scientific literature on this issue. Our thorough and critical review of the
published literature on EDTA chelation, which includes numerous case studies and
testimonials, identified only two scientifically rigorous clinical trials, neither of
which found any benefit of the therapy.
In August 1991 and early 1992, researchers in Denmark published results from a clinical
trial of 153 patients with intermittent claudication, an atherosclerosis-related condition
characterized by pain and weakness in the legs that is exacerbated by walking. The
patients were divided into two groups. Patients in one of the groups received intravenous
EDTA, while the other group of patients the
control group received a "dummy" or
placebo therapy of intravenous saline solution. The scientists measured patient walking
distances before, during, and after treatment. They found similar improvements in walking
distance in both groups those patients who had
received the EDTA treatment and those who had received the placebo treatment. The
scientists noted that the results reflect "the
well-known phenomenon of spontaneous improvement,"
commonly known as the "placebo effect"
in which patients feel or function better for
no reason other than that they are being treated or observed. They concluded that EDTA
chelation therapy had no beneficial effect among the patients in the trial.
In 1994, a group of New Zealand researchers published results from a similar clinical
study of 32 patients with intermittent claudication. Here again, the patients were divided
into two groups. Fifteen of the patients underwent EDTA chelation therapy, and 17 patients
were given a placebo of saline solution. As in the Danish study, walking distance was used
as the major measure of improvement. At the end of the treatment period, 60 percent of the
chelation group showed an increase in walking distance. However, 59 percent of the saline
or placebo group also demonstrated such an improvement. As with the Danish study, these
results again provide a classic illustration of the placebo effect that is, improvement that springs from the mere fact
of being treated, rather than from the results of the specific treatment itself. The New
Zealand scientists therefore concluded, like the Danish researchers, that EDTA chelation
therapy has no significant beneficial effects.
Both of these high-quality studies are referenced in an NHLBI fact sheet that we
developed to respond to the many inquiries we receive regarding chelation therapy. We
based our comments on only these two studies because they are the only ones that meet the
standard of scientific rigor needed to make recommendations affecting people's health. A 1997 literature review published in the
American Heart Association's peer-reviewed
journal, Circulation, likewise found that the Danish and New Zealand studies were
the only two of "outstanding methodological
rigor" on the issue of EDTA chelation therapy.
One might ask why the NHLBI does not consider case reports and testimonials in its
examination of chelation therapy. The reality is that such uncontrolled observations,
while suggestive, do not enable us to identify the singular value of a particular
approach. In clinical trials, patients are divided into two groups those who receive the treatment and those who do
not. Assignment to the groups is random, and neither the patients nor the researchers know
up front who will be getting the treatment and who will be getting the placebo. Thus, the
very design of clinical trials paves the way for unbiased results that can be compared
with great confidence that variables other than the intervention itself are held constant.
Clinical trials also ensure that the effects being observed are, indeed, due to the
treatment and not just the result of a placebo effect.
Clinical trials are an especially important standard in the issue of chelation therapy
because the novel concepts and claims involved in alternative medicine naturally call for
systematic and explicit review. The National Institutes of Health's (NIH) National Center for Complementary and
Alternative Medicine (formerly Office of Alternative Medicine) applies research methods at
least as rigorous, if not more so, than those used as the current standard in conventional
medicine.
The NHLBI is not the only agency or organization that has expressed concern about the
value of chelation therapy for atherosclerosis. The American Medical Association, the
American Heart Association, the American College of Cardiology, and the Food and Drug
Administration all hold that EDTA chelation therapy remains a scientifically unproven
technique for treating atherosclerosis.
The fact that there are only two studies that meet the public health standards of
scientific rigor illustrates a central problem in the EDTA chelation controversy: Neither
scientists who possess the knowledge and experience to evaluate the treatment nor
practitioners who offer it have looked at it carefully. In fact, although the NHLBI has
received tens of thousands of research grant applications over the past 30 years, only 3
have addressed this topic, and none of them met the high standards of scientific quality
that NHLBI funding demands.
The issue of EDTA chelation therapy for atherosclerosis was addressed in 1993 by the
first Director of the NIH Office of Alternative Medicine (OAM; now the National Center for
Complementary and Alternative Medicine), who contracted with an investigator at the
University of Washington to explore the topic. The following year, staff of the NHLBI and
the OAM began working collaboratively with this investigator to develop a protocol for a
clinical trial. Following much discussion, the investigator wrote an application which the
NHLBI was eager to receive for review in June 1996. Unfortunately, in the eleventh hour
his institution withdrew its endorsement of the effort and the formal application never
materialized.
Subsequently, the investigator passed his protocol on to researchers at the University
of Missouri, and we continued our efforts to bring the project to fruition. This endeavor
resulted in a grant application that was received in June 1998 and reviewed by the NHLBI
Clinical Trials Review Committee in October 1998. Unfortunately, the non-federal
scientists who evaluated this application identified a number of shortcomings that would
compromise the ability of the proposed research to resolve the controversy. A member of
the Institute's staff has since been in
communication with the investigator to explore ways to address the criticisms raised in
the review. At this time we do not know whether the investigator plans to submit a revised
application, but we would be pleased to accept such an application for re-review if he
chooses to do so.
Atherosclerosis is a major underlying cause of death in developed countries. It leads
to coronary heart disease, the leading cause of death in this country, as well as stroke,
the third leading cause of death. If EDTA chelation therapy proved to be a valid
intervention for atherosclerosis, millions of people might benefit. Until such proof comes
to light, however, we cannot recommend its use.
The NHLBI is ready and willing to work with qualified researchers to resolve this
important public health issue. The vast majority of research at NIH is
investigator-initiated that is, the
investigator proposes the research and, if his or her application is successful in
competing for funding, carries out the research. If the scientific and clinical
communities share our interest in resolving the issue of the effectiveness of EDTA
chelation therapy in the treatment of atherosclerosis, experts with strong study protocols
must step up to the plate and apply for funding.
I would be pleased to answer any questions the Committee may have.
