- What
is laetrile?
Laetrile is a compound that
has been used as a treatment for people with cancer worldwide.
It is not approved by the U.S.
Food and Drug Administration (FDA)
as a treatment for cancer or any other medical condition.
The term laetrile comes
from 2 words (laevorotatory and mandelonitrile) and is used to describe
a purified form of the chemical amygdalin.
Amygdalin is a plant compound that contains sugar and produces hydrogen cyanide.
Hydrogen cyanide is thought to be the main anticancer compound formed
from laetrile when broken down in the body. Amygdalin is found in the
pits of many fruits and in raw nuts. It is also found in other plants
such as lima beans, clover, and sorghum.
The
names laetrile, Laetrile, vitamin B-17, and amygdalin are often used in
place of one another, but they are not the same product. The chemical
make-up of Laetrile patented in the United States is different from the
laetrile/amygdalin produced in Mexico. The patented Laetrile is a partly synthetic (man-made)
form of amygdalin, while the laetrile/amygdalin made in Mexico comes
from crushed apricot pits. The studies discussed in this fact sheet
used either Mexican laetrile/amygdalin or Laetrile. The generic term laetrile will be
used throughout this summary except in cases when the patented version
of Laetrile is known to have been used in a study.
- What
is the history of the discovery and use of laetrile as a complementary
or alternative treatment for cancer?
Amygdalin
was first isolated in 1830 and was used as an anticancer agent in
Russia as early as 1845. Its first recorded use in the United States as
a treatment for cancer was in the 1920s. The early pill form of
amygdalin was found to be too toxic,
and work with the compound was stopped. In the 1950s, a reportedly nontoxic,
partly synthetic form of amygdalin was made and patented in the United
States as Laetrile. Laetrile gained popularity in the 1970s as a single
anticancer agent and as part of a metabolic
therapyprogram that included a special diet,
high-dose vitamin supplements,
and pancreatic
enzymes (a
group of proteins that
aid in the digestion of
food). By 1978, more than 70,000 people in the United States had
reportedly been treated with Laetrile.
In
1980, the U.S. Supreme Court upheld a ban on the shipment of laetrile
between states in the United States. It is still used in Mexico and at
some clinics in the United States.
- What
is the theory behind the claim that laetrile is useful in treating
cancer?
Hydrogen
cyanide is thought to be the main anticancer ingredient in laetrile.
Two other breakdown products of amygdalin, prunasin (which is similar
in structure to laetrile) and benzaldehyde,
may also be cancer cell blockers.
The following theories have been proposed to support the use of
laetrile for cancer:
- Two
of the theories state that the balance of certain enzymes in
cancer cells allows laetrile to be toxic to the
cancer cells. There is some evidence that normal tissues and malignant tissues
do have different amounts of these enzymes.
- Another
theory states that cancer is the result of a vitamin deficiency and
that laetrile, or amygdalin/vitamin
B-17, is the missing vitamin needed by the body to restore
health. There is currently no evidence that laetrile is needed by the
body or that laetrile can act as a vitamin in animals or humans.
- The
fourth theory states that the cyanide released by laetrile has a toxic
effect that results in killing the cancer cells and stopping them from
growing. The theory also states that the damage to the cells causes a
boost to the immune
system.
- How
is laetrile administered?
Laetrile
is given by mouth (orally)
as a pill. It can also be given by injection into a vein(intravenously)
or muscle. Laetrile is commonly given intravenously over a period of
time and then orally as maintenance
therapy (treatment
given to help extend the benefit of previous therapy).
- Have
any preclinical (laboratory or animal) studies been conducted using
laetrile?
Preclinical
studies have
been done with laetrile either alone or combined with other substances.
These studies tested the benefits of laetrile against cancer, the side
effectsof laetrile treatment, where and how laetrile
breaks down in the body, and how laetrile and its breakdown products
leave the body. Laboratory and animal
studies have
shown mixed results on the anticancer effects of laetrile (amygdalin).
Two
animal studies of amygdalin by the National
Cancer Institute reported
no responsewhen
it was given alone or with an enzyme that activates the release of
cyanide from amygdalin in the body. The animals had more side effects
when the enzyme was given at the same time as the amygdalin. Similar
results were reported when human breastand colon tumors were
implanted into mice.
Other
studies have reported the following responses to amygdalin:
- A
laboratory study of amygdalin reported that it somewhat slowed the
growth of colon
cancer cells.
- A
laboratory study of amygdalin reported the higher the dose of
amygdalin, the more likely the prostate
cancer cells
were to respond.
- A
laboratory study of amygdalin given with beta-D-glucosidase reported a
time and dose-dependent response
in hepatoma cells.
The longer amount of time that amygdalin and beta-D-glucoside were
given and the higher the dose, the more likely the hepatoma cells were
to respond.
- A
laboratory study of amygladin reported the higher the dose of
amygdalin, the more likely the cervical
cancer cells
were to respond.
- One
study in rats reported that amygdalin was not effective at treating, preventing,
or delaying development of tumors.
- One
study reported tumor response in mice with mammary tumors
when amygdalin was given with enzymes and vitamin
A, but not when given alone.
- Have
any clinical trials (research studies with people) of laetrile been
conducted?
No controlled
clinical trials (trials
that compare groups of patients who receive the new treatment to groups
who do not) of laetrile have been reported.
Although
many anecdotal
reports (incomplete
descriptions of the medical/treatment history of one or more patients)
and case
reports (detailed
reports of the diagnosis,
treatment, and follow-up of
individual patients) are available, they provide little evidence to
support laetrile as a treatment for cancer.
The
following has been reported from case series about the use of laetrile
in patients with cancer:
- A case
series (a
group or series of case reports involving patients who were given
similar treatment) of 44 patients treated with laetrile was published
in 1953. Most of the patients who showed some improvement also received radiation
therapy or
anticancer drugs,
so it is not known which treatment produced the benefit.
- In
another series of case reports published in 1962, 10 patients with metastatic
cancer (cancer
that has spread from one part of the body to another) were treated with
a wide range of doses of intravenous Laetrile. Pain relief was the main
reported benefit. Reduced swelling of lymph
nodes and
decreased tumorsize
were also reported. Long-term follow-up with these patients was not
done, however, so it is not known how long the benefits lasted after
treatment.
- Benzaldehyde,
which is made when laetrile is broken down by the body, has also been
tested for anticancer activity in humans. In two clinical
series (case
reports of a number of patients who are treated consecutively in a
clinic), patients with advanced
cancer who
had not responded to standard
therapy were
treated with benzaldehyde. Some patients had a complete
response (the
disappearance of all signs and symptoms of
cancer), while some had a decrease in tumor size. The responses to
benzaldehyde lasted as long as the treatment continued. Almost all of
the patients had been treated previously with chemotherapy or
radiation therapy, but it is not known how soon treatment with
benzaldehyde began after the other treatment ended.
- In
1978, the National
Cancer Institute (NCI)
requested case reports from practitioners who
believed their patients were helped by treatment with laetrile.
Ninety-three cases were submitted; 67 of these were complete enough to
be evaluated. An expert panel concluded that 2 of the 67 patients had
complete responses and 4 others had a decrease in tumor size. Based on
these 6 cases, NCI sponsored clinical
studies with
laetrile.
Findings
from only 2 clinical
trials with
laetrile have been published. These trials, sponsored by NCI, were done
in the late 1970s and early 1980s, and did not include a control
group for
comparison.
The
following has been reported from these 2 clinical trials about the use
of laetrile in patients with cancer:
- The
first trial, a phase
I study, tested doses, schedules,
and ways to give amygdalin in 6 cancer patients. Researchers found that
amygdalin caused very few side effects when given by mouth or
intravenously. Two patients who ate raw almonds while taking amygdalin,
however, developed symptoms of cyanide poisoning.
- In
1982, a phase
II study with
175 patients looked at which types of cancer might benefit from
treatment with amygdalin. Most of the patients in this study had breast, colon,
or lung
cancer. Amygdalin was given by injection for 21 days,
followed by oral maintenance therapy using doses and procedures similar
to those in the phase I study. Vitamins and pancreatic enzymes were
also given as part of a metabolic therapy program that also included dietary changes.
One stomach
cancer patient
showed a decrease in tumor size, which was maintained for 10 weeks
while the patient was on amygdalin therapy. In about half of the
patients, cancer had grown at the end of the treatment. Cancer had
grown in all patients 7 months after completing treatment. Some
patients reported an improvement in their ability to work or do other
activities, and other patients said their symptoms improved. These
improvements, however, did not last after treatment ended.
- Have
any side effects or risks been reported from laetrile?
The
side effects of laetrile treatment are like the signs and
symptoms of cyanide poisoning. These include:
- Nausea and vomiting.
- Headache.
- Dizziness.
- Blue
color of the skin due to a lack of oxygen in the blood.
- Liver damage.
- Abnormally low blood
pressure.
- Droopy
upper eyelid.
- Trouble
walking due to damaged nerves.
- Fever.
- Mental confusion.
- Coma.
- Death.
The
side effects of laetrile appear to depend on the way it is given. Side
effects are more severe when laetrile is given by mouth than when it is
given by injection. These side effects may be increased by:
- Eating
raw almonds or crushed fruit pits.
- Eating
certain types of fruits and vegetables, including celery, peaches, bean
sprouts, and carrots.
- Taking
high doses of vitamin
C.
- Is
laetrile approved by the FDA for use as a cancer treatment in the
United States?
The
U.S. Food and Drug Administration (FDA) has not approved laetrile as a
treatment for cancer in the United States. The drug is made and used as
a cancer treatment in Mexico.
Laetrile
compounds from Mexico, which is the primary supplier of laetrile, may
vary in purity and contents. Products containing bacteria and
other substances and products labeled incorrectly have been found.
