Unconventional Cancer Therapies
Laetrile / Amygdalin
/ Vitamin B17 / Sarcarcinase / Nitriloside
The role of your cancer health professional is to create an environment of openness and trust, and to help in making informed decisions about alternative/complementary therapies. Collaboration will improve the safe integration of all therapies during your experience with cancer. The "Summary" and "Professional Evaluation / Critique" sections of this Unconventional manual are cited directly from the medical literature, and are intended to help in the objective evaluation of alternative/complementary therapies.
In 1980, the National Cancer Institute began a clinical study of
laetrile in terminal cancer patients. "Conducted in collaboration with
"Moreover, laetrile has been banned by the FDA because of the risk of poisoning from its cyanide content." (Fetrow)
Description / Source / Components
Although not chemically identical, amygdalin and Laetrile are terms frequently used interchangeably. Both belong to a family of compounds called cyanogenic glycosides.
"It is also sometimes referred to as vitamin B17,
although it is definitely not a vitamin." (
"It is obtained from the kernels of apricots, peaches, plums, cherries, nectarines, apples, and almonds." (Fetrow)
"Amygdalin occurs naturally in a
number of plant materials; however, the usual commercial source is the kernel
of various varieties of Prunus armeniaca L. (family Rosacea),
commonly referred to as apricot pits. These vary appreciably in there amygdalin or laetrile content, which may reach 8 percent,
but the kernels of some wild varieties contain twenty times as much as those of
cultivated varieties of apricots." (
"Laetrile is a poisonous chemical found in the kernels of
some fruits and nuts." (
"Laetrile (amygdalin) is a cyanogenic glycoside that was proposed for cancer treatment on the basis that it would be broken down by an enzyme in cancerous tissue to liberate cyanide which would 'kill the cancer'." (Jukes)
"Amygdalin is a naturally occurring cyanogenic glycoside, which can be cleaved by sweet almond beta-glucosidase to yield free cyanide." (Syrigos)
Amygdalin, when extracted from oil of bitter almonds, yields 2 units of glucose, 1 unit of benzaldehyde, and 1 unit of hydrogen cyanide. (White)
"Laetrile is most commonly given intravenously for two to three
weeks. This treatment is followed by oral doses for maintenance therapy."
Amygdalin, perhaps first documented by Dioscorides of Anazarbos 2,000 years ago, is usually administered in the form of bitter almonds. (Moertel)
It was "rediscovered" in 1920 by a
"Laetrile was developed by Ernst T. Krebs, Sr., MD, and his
son Ernst T. Krebs, Jr., and was first used to treat cancer patients in
"The Committee for Freedom of Choice in Medicine is the political arm of several interlocking corporations promoting and/or marketing questionable remedies for cancer and other serious disease. Operating during the 1970s as the Committee for Freedom of Choice in Cancer Therapy, the organization fought for legalization of Laetrile and claimed to have many members. Today the committee appears to be a small group whose principal activities are speeches and press conference by its leaders, protests to government agencies, and publication of a small circulation newsletter." (CA 1993)
"Lacking any proof of safety and efficacy, the Food and Drug
Administration banned laetrile from interstate commerce in 1971. However,
several state legislatures, reacting to political pressures, legalized
intrastate sale and use of the product. In 1980, similar pressures forced the
National Cancer Institute to begin a clinical study of laetrile in terminal
cancer patients." (
"...its 1970 popularity waned even before the 1982 publication of a Mayo Clinic investigation showing its ineffectiveness." (Cassileth)
Proponent / Advocate Claims
"The noted biochemist Ernest Krebs, Jr., PhD., first specifically identified amygdalin as an anticancer agent. His discovery was based on a theory that cancer grows from misplaced trophoblast cells; these are cells found in a pregnant human uterus that multiply rapidly during the first few weeks after conception. Under normal, healthy conditions, trophoblast cells are destroyed by the pancreatic enzyme, chymotrypsin. If they escape destruction, they can lodge in the embryo and remain there, dormant, for decades, waiting to develop into a tumor when the pancreas becomes dysfunctional." (Diamond)
Laetrile advocates advance two theories:
1. Cyanide Release Theory
"Advocates of laetrile therapy for cancer believe that an
enzyme, beta-glucosidase, capable of breaking down
the laetrile to release toxic cyanide, exists in large amounts in tumorous tissue but only in small quantities in the rest of
the body. They further hypothesize that another enzyme, rhodanese
(sic), which has the ability to detoxify cyanide, is present in normal tissues
but deficient in cancer cells. These two factors supposedly combine to effect a
selective poisoning of cancer cells by the cyanide released from the laetrile,
while normal cells and tissues remain undamaged." (
Beta-glucosidase, an enzyme occurring in malignant neoplasms, was believed to release sufficient amounts of hydrogen cyanide from Laetrile to stop tumour respiration and thus destroy cancerous tissue. (Levi)
2. Vitamin Deficiency Theory
Cancer is a vitamin deficiency disease, and Laetrile is the missing "vitamin B17". (Martin 1983)
Professional Evaluation / Critique
"The National Cancer Institute (NCI) sponsored an independent study of Laetrile with cancer patients. Fifty-four percent of the 178 patients had measurable cancer progression after 21 days of intravenous treatment with Laetrile. After 3 months, 91 percent had disease progression, and after 7 months, all patients' tumors had grown larger. Very few patients reported any change in their symptoms. Half of all patients in the study died within 5 months after starting treatment; within 8 months, 85 percent were dead." (National Cancer Institute)
"NCI tested Laetrile in laboratory animals several times but found no convincing evidence that it is effective against animal cancers." (National Cancer Institute)
"Consumption of peach kernels is potentially fatal, and there are no valid clinical studies documenting the effectiveness of hydrocyanic acid in the prevention or treatment of cancer. The potential risks associated with the consumption of peach kernels outweigh any potential benefits, and their used should be discouraged." (Fetrow)
No evidence is available to support either of the proposed theories. All data published in reputable scientific journals reveal that Laetrile has no selective antitumor activity against either animal or human cancers. (Martin 1983)
1. Cyanide Release Theory
Dr. Charles G. Moertel described a clinical trial involving 178 patients. Patients were selected who had histologically proven cancer for which no standard treatment was known to be curative or to extend life expectancy. All patients had had no surgery, radiation therapy or chemotherapy for one month. The amygdalin used for treatment was prepared from apricot pits and supplied by the Pharmaceutical Resources Branch of the National Cancer Institute.
Patients selected were in good general condition, were ambulatory and able to maintain good nutrition. Patients who were disabled and bedridden were ineligible for the study.
The routes, dosage and schedule of administration were chosen to be representative of current Laetrile practice. Patients were also placed on a diet identical to the one recommended by most Laetrile practitioners.
"Each patient had either a tumor area which could be measured in two dimensions or malignant hepatomegaly with a clearly defined liver edge extending at least 5 cm below the costal margin. Lesions demonstrable by radioisotope liver scan or by computerized tomographic scan were accepted if they measured 5 cm in diameter." (Moertel)
Of 171 fully documented patients, only one patient met the criteria for partial response. However, all patients had tumor progression by 7 months.
"The fact that amygdalin therapy did not slow the advance of malignant disease or induce "stabilization" is evidenced by the fact that more than half these patients had measurable tumor progression when they terminated the intravenous induction therapy and that over 90 percent had progression by 3 months." (Moertel)
2. Vitamin Deficiency Theory
A vitamin is defined on the basis of several properties not applying to Laetrile:
- A vitamin is required in small amounts for the complete health and well-being of vertebrate organisms.
- Vitamins are not used primarily to supply energy or as a source of structural tissue components of the body.
- A vitamin promotes physiological processes vital to the continued existence of the organism.
- A vitamin (except vitamin A) cannot be synthesized by the cells of the organism.
- In man, deficiency of a specific vitamin is the cause of certain well-defined diseases. These diseases are cured or prevented by the addition of the appropriate vitamin. (Greenberg)
The following facts have been established about Laetrile (incorrectly called vitamin B17):
1. Laetriles are not essential nutritional components.
2. Laetriles have never been shown to promote any vital physiological processes.
3. No specific disease has been associated with a lack of Laetrile. (Greenberg)
Laetrile may be a carcinogen (itself cause cancer); mutagenic effects have been observed as determined by the Ames Salmonella lyphimurium test. (Fenselan)
Two researchers in
An inquiry reported in the New York Times in 1977 revealed a profit of $150,000 to $200,000 a month to one Laetrile promoter. (Martin 1977)
Toxicity / Risks
"A clinical trial conducted at the Mayo Clinic and three other prominent cancer centers found no anticancer effect but found significant blood levels of cyanide in some of the patients." (Hafner)
While taking Laetrile, patients may suffer nausea, vomiting, headache,
and dizziness. (
"Symptoms following cyanide poisoning include sudden, severe vomiting and epigastric pain followed by syncope [a faint], lethargy, coma, and seizures. Chronic consumption of plants high in cyanogenic glycosides has resulted in optic atrophy [a wasting away of the optic disc], nerve deafness, spastic paraparesis [a partial paralysis of the lower extremities], ataxia [failure of muscular coordination], clonus [alternate muscular contraction and relaxation in rapid succession], and peripheral neuropathy." (Fetrow)
"Serious cases of poisoning have been reported as a result of
eating quantities of these seeds." (
Several patients participating in the clinical trial conducted by Moertel had symptomatic toxicity (nausea and vomiting, headache, dizziness, mental obtundation, dermatitis). These symptoms subsided promptly when oral amygdalin was discontinued. They were sometimes (but not always) associated with relatively high levels of blood cyanide. The cyanide approached levels known to be lethal to animals. (Moertel)
"In addition, the Laetrile was generally available from Mexican suppliers and was found to be contaminated with infectious agents and endotoxin. Deaths attributable to laetrile have been reported." (Spencer)
Taken by injection, amygdalin is non-toxic, however, when a source of beta-glucosidase is injected with amygdalin, the toxicity is greatly increased. Orally administered, amygdalin is definitely toxic, presumably due to the presence of beta-glucosidase in the small intestine. (Greenberg)
Ingested with plant material containing beta-glucosidase, amygdalin can be lethal. (Schmidt)
Two reports of deaths from swallowing amygdalin preparations intended for the treatment of cancer have been published, one of a child (Humbert); the other of a seventeen year old girl. (Sadoff)
A three year old boy suffering from leukemia died in
A woman suffering from breast cancer died of cyanide poisoning
after taking massive doses of Laetrile. (
Prolonged ingestion of cyanogenic
glycoside-containing plant food stuffs is suspected of being a cause of
tropical amblyopia (dimness of vision) and other
obscure neurological disorders. (
"Laetrile is usually given as part of a larger treatment program which can cost between $2,000 to $5,000
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Revised February 2000