|
Other common
name(s): amygdalin, vitamin B17, Amigdalina B-17
Scientific/medical
name(s): mandelonitrile beta-D-gentiobioside,
mandelonitrile-beta-glucuronide
Description
Laetrile is a chemically modified form of amygdalin, a
naturally-occurring substance found mainly in the kernels of apricots,
peaches, and almonds. However, the terms amygdalin and Laetrile are
often used interchangeably. The name Laetrile is also used to describe
a closely related, man-made substance. Laetrile and amygdalin are
promoted as alternative cancer treatments.
Overview
Available scientific evidence does not support claims that
Laetrile or amygdalin are are effective in treating cancer or any other
disease. Both contain a small amount of a substance that can be
converted to cyanide in the body, and several cases of cyanide
poisoning have been linked to the use of Laetrile. The U.S. Food and
Drug Administration (FDA) has not approved Laetrile as a medical
treatment in the United States.
How is it promoted for use?
Supporters once called Laetrile "the perfect chemotherapeutic
agent," as it was said to kill cancer cells while being non-toxic to
normal cells. Promoters claim that societies with diets rich in
amygdalin, such as the Hunza and the Karakorum, are "cancer-free
peoples." Supporters also say that Laetrile can prevent cancer and can
help patients stay in remission. It is also promoted to provide pain
relief to people with cancer. Other reported uses for Laetrile have
been in the prevention and treatment of high blood pressure and
arthritis.
There are several proposed explanations for how Laetrile
works. Supporters claim that cancer cells contain more of a certain
enzyme that splits the Laetrile molecule and releases the cyanide
within it. The cancer cell then supposedly dies from cyanide poisoning.
Normal cells supposedly do not have as much of this enzyme and instead
contain an enzyme that renders the Laetrile harmless. Supporters claim
that normal cells are not affected for this reason.
Another popular theory is that cancer is really a "vitamin
deficiency" and that Laetrile is the missing "vitamin B17." Laetrile
does not meet the widely accepted scientific definition of a vitamin,
in that it has not been proven to be essential to achieving or
maintaining good health.
What does it involve?
Amygdalin is most commonly extracted from apricot pits.
Laetrile is a related substance, which has a slightly different
chemical structure. Laetrile or amygdalin are often taken as part of a
metabolic therapy that includes a specific diet with high doses of
vitamins (see Metabolic Therapy).
Although no standard treatment plan exists, a typical treatment
consists of injecting Laetrile or amygdalin into a vein each day for 2
to 3 weeks, followed by taking tablets by mouth as a maintenance
therapy. Laetrile and amygdalin are also used in enemas and in
solutions applied directly to skin lesions. Chemical analyses of
products sold as Laetrile showed that the actual ingredient is often
amygdalin rather than Laetrile. For this reason, and because the terms
are often used as synonyms, both substances are called Laetrile in the
remainder of this document unless otherwise noted.
Laetrile treatments may cost thousands of dollars per week.
Laetrile is commonly used in some hospitals and clinics in northern
Mexico because it is difficult to get in the United States.
What is the history behind it?
"Bitter almonds" have been used as a medical remedy for
thousands of years by cultures as diverse as the ancient Egyptians,
Chinese, and Pueblo Indians. In 1802, a chemist discovered that
distilling the water from bitter almonds released hydrocyanic acid. In
the 1830s, the source of this hydrocyanic acid was purified and called
amygdalin. It was thought to be the active ingredient in bitter
almonds.
According to a 1991 review, the current use of Laetrile can be
directly attributed to the theories of Ernst T. Krebs, Sr., MD, which
were first proposed in the 1920s. Krebs tested an extract from apricot
pits to treat cancer, but the pills proved too toxic for human use.
Around 1952, his son, Ernst T. Krebs, Jr., changed the process
of extracting amygdalin and created a chemically modified version,
which he named Laetrile. He claimed that the new substance was more
potent as an anti-cancer drug than naturally occurring amygdalin.
Despite this chemical distinction, both proponents and skeptics
commonly refer to both substances as Laetrile. Adding to this confusion
is the fact that many products sold as Laetrile consist mostly of
amygdalin.
The same 1991 review notes that, beginning in 1957, Laetrile
was repeatedly tested against tumor cells implanted in animals. At
least a dozen separate sets of experiments were done at seven
institutions. Targets included several different types of cancer. The
conclusion was that Laetrile did not have any anti-tumor activity.
The FDA placed sanctions against the sale of Laetrile. In
1977, the FDA commissioner stated that there was no evidence for the
safety or effectiveness of Laetrile. Because of the risk of cyanide
poisoning, the government has banned the transport of Laetrile into the
United States or across state lines, as well as the use of Laetrile in
states without laws specifically allowing it. Since 2000, there have
been several instances of prosecution because of Laetrile transport
across state lines.
What is the evidence?
From the 1950s through the 1970s, Laetrile grew in popularity
in the United States as an alternative treatment for cancer. For this
reason, and despite the lack of scientific evidence that Laetrile was
effective, the National Cancer Institute (NCI) studied it in 1978
through a retrospective case review (a study that looks back at cases
from the past). The NCI sent letters to more than 400,000 doctors and
other practitioners, asking them to submit positive results from cases
involving Laetrile. While an estimated 75,000 people in the United
States had taken Laetrile, only 93 "positive" cases were submitted, and
in only 6 of those was there evidence of major tumor shrinkage.
A 1991 NCI review of the evidence of Laetrile’s
effectiveness stated that "scientific studies were conducted for more
than 20 years, starting in the mid-1950s, looking for evidence of
antitumor efficacy by Laetrile. In no instance was evidence found that
treatment with Laetrile results in any benefit against tumors in
animals. Despite this negative record, a clinical trial in humans was
conducted in 1981. It did not show any anticancer effect of Laetrile."
The clinical trial of Laetrile on humans was performed between
1979 and 1981 at medical centers around the country. About 175 patients
with different types of cancer were treated with a commonly used
regimen of Laetrile plus metabolic therapy (see Metabolic Therapy).
Published in 1982, it reported that one patient had major tumor
shrinkage (a partial response) at first. Of the patients, 91% of their
cancers had progressed after 3 months, and median survival was less
than 5 months. In all patients, their cancer grew within 8 months of
starting treatment.
In contrast to the findings the NCIs findings, one of the
leading proponents of Laetrile claims to have treated nearly 30,000
cancer patients in several studies of the drug with promising results.
However, these results have not been reviewed or repeated by the
scientific medical community.
The consensus of available scientific evidence does not
support claims that Laetrile is an effective anti-cancer treatment,
either in animal studies or in human clinical trials. Cancer cells do
not seem to be more susceptible to the effects of Laetrile than normal
cells. The successes claimed by its supporters are based on individual
reports, testimonials, and publicity issued by promoters.
Are there any possible problems or
complications?
This substance
may not have been thoroughly tested to find out how it interacts with
medicines, foods, or dietary supplements. Even though some reports of
interactions and harmful effects may be published, full studies of
interactions and effects are not often available. Because of these
limitations, any information on ill effects and interactions below
should be considered incomplete.
The use of Laetrile has been linked to cyanide toxicity and
death in a few cases. Although drug interactions are unknown, at least
one case report suggests that vitamin C may increase the amount of
cyanide released from Laetrile in the body. This can increase the risk
of cyanide poisoning. This risk is also likely to be increased if the
person also eats raw almonds or crushed fruit pits while taking
Laetrile. Eating fruits and vegetables that contain beta-glucosidase
(such as celery, peaches, bean sprouts, and carrots) may increase the
risk of cyanide poisoning. Always tell your doctor and pharmacist about
any supplements or herbs you are taking.
This treatment should be avoided by children, and by women who
are pregnant or breast-feeding. Relying on this type of treatment
alone, and avoiding or delaying conventional medical care for cancer,
may have serious health consequences.
Additional Resources
More information from your American Cancer
Society
The following information on complementary and alternative
therapies may also be helpful to you. These materials may be found on
our Web site (www.cancer.org)
or ordered from our toll-free number (1-800-ACS-2345).
References
American Cancer Society. Unproven methods of cancer
management. Laetrile. CA
Cancer J Clin. 1991;41:187-192.
Bromley J, Hughes BG, Leong DC, Buckley NA. Life-threatening
interaction between complementary medicines: cyanide toxicity following
ingestion of amygdalin and vitamin C. Ann Pharmacother.
2005;39:1566-1569.
Ellison NM, Byar DP, Newell GR. Special report on Laetrile:
the NCI Laetrile review. Results of the National Cancer
Institute’s retrospective Laetrile analysis. N Engl J Med.
1978;299:549-552.
Fetrow CW, Avila JR. Professional’s
Handbook of Complementary and Alternative Medicines.
Springhouse, Pa: Springhouse Corp; 1999.
Herbert V. Laetrile: The Cult of Cyanide: Promoting Poison for
Profit. Am J Clin Nutr.
1979;32:1121-1158.
Lerner IJ. Laetrile: a lesson in cancer quackery. CA Cancer J Clin
1981;31:91-95.
Memorial Sloan-Kettering Cancer Center. About herbs:
Amygdalin. 2006. Accessed at: www.mskcc.org/mskcc/html/69118.cfm on
June 11, 2008.
Milazzo S, Lejeune S, Ernst E. Laetrile for cancer: a
systematic review of the clinical evidence. Support Care Cancer.
2006.
Moertel CG, Fleming TR, Rubin J, et al. A clinical trial of
amygdalin (Laetrile) in the treatment of human cancer. N Engl J Med.
1982;306:201-206.
National Cancer Institute Physician Data Query (PDQ).
Laetrile/Amygdalin. 2006. Accessed at:
www.cancer.gov/cancertopics/pdq/cam/laetrile/healthprofessional on June
11, 2008.
Wilson B. The rise and fall of laetrile. 2004. Accessed at:
www.quackwatch.org/01QuackeryRelatedTopics/Cancer/laetrile.html on June
11, 2008.
Note:
This
information may not cover all possible claims, uses, actions,
precautions, side effects or interactions. It is not intended as
medical advice, and should not be relied upon as a substitute for
consultation with your doctor, who is familiar with your medical
situation.
Last Medical Review: 11/01/2008
Last Revised: 11/01/2008
|
