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- Summary of the Evidence for Laetrile/Amygdalin
- Changes to This Summary (08/10/2012)
- About This PDQ Summary
This complementary and alternative medicine (CAM) information summary provides an overview of the use of laetrile as a treatment for people with cancer. The summary includes a history of laetrile research, a review of laboratory studies, the results of clinical trials, and possible side effects of laetrile use.
This summary contains the following key information:
- Laetrile is another name for the chemical amygdalin, which is found in the pits of many fruits and in numerous plants.
- Cyanide is thought to be the main anticancer component of laetrile.
- Laetrile was first used as a cancer treatment in Russia in 1845, and in the United States in the 1920s.
- Laetrile has shown little anticancer activity in animal studies and no anticancer activity in human clinical trials.
- Laetrile is not approved for use in the United States.
- Inappropriate advertisement of laetrile as a cancer treatment has resulted in a U.S. Food and Drug Administration investigation that culminated in charges and conviction of one distributor.
Many of the medical and scientific terms used in the summary are hypertext linked (at first use in each section) to the NCI Dictionary of Cancer Terms, which is oriented toward nonexperts. When a linked term is clicked, a definition will appear in a separate window.
Reference citations in some PDQ CAM information summaries may include links to external Web sites that are operated by individuals or organizations for the purpose of marketing or advocating the use of specific treatments or products. These reference citations are included for informational purposes only. Their inclusion should not be viewed as an endorsement of the content of the Web sites, or of any treatment or product, by the PDQ Cancer CAM Editorial Board or the National Cancer Institute.
The term “laetrile” is an acronym (laevorotatory and mandelonitrile) used to describe a purified form of the chemical amygdalin, a cyanogenic glucoside (a plant compound that contains sugar and produces cyanide) found in the pits of many fruits and raw nuts and in other plants such as lima beans, clover, and sorghum. Reviewed in  In the 1970s, laetrile gained popularity as an anticancer agent. By 1978, more than 70,000 individuals in the United States were reported to have been treated with it. Reviewed in  Laetrile has been used for cancer treatment both as a single agent and in combination with a metabolic therapy program that consists of a specialized diet, high-dose vitamin supplements, and pancreatic enzymes. Reviewed in 
In the United States, researchers must file an Investigational New Drug (IND) application with the US Food and Drug Administration (FDA) to conduct drug research in human subjects. In 1970, an application for an IND to study laetrile was filed by the McNaughton Foundation (San Ysidro, California). This request was initially approved but later rejected because preclinical evidence in animals showed that laetrile was not likely to be effective as an anticancer agent, Reviewed in  and because there were questions about how the proposed study was to be conducted. Reviewed in  Laetrile supporters viewed this reversal as an attempt by the U.S. government to block access to new and promising cancer therapies, and pressure mounted to make laetrile available to the public. Court cases in Oklahoma, Massachusetts, New Jersey, and California challenged the FDA’s role in determining which drugs should be available to cancer patients. Consequently, laetrile was legalized in more than 20 states during the 1970s. In 1980, the U.S. Supreme Court overturned decisions by the lower courts, thereby reaffirming the FDA’s position that drugs must be proven to be both safe and effective before widespread public use. Reviewed in  As a result, the use of laetrile as a cancer therapy or as a treatment for any other medical condition is not approved in the United States, but the compound continues to be manufactured and administered as an anticancer therapy, primarily in Mexico.
Although the names laetrile, Laetrile, and amygdalin are often used interchangeably, they are not the same product. The chemical composition of US-patented Laetrile (mandelonitrile-beta-glucuronide), a semisynthetic derivative of amygdalin, is different from the laetrile/amygdalin produced in Mexico (mandelonitrile beta-D-gentiobioside), which is made from crushed apricot pits. Reviewed in  Mandelonitrile, which contains cyanide, is a structural component of both products. Reviewed in  It has been proposed that cyanide is the active cancer-killing ingredient in laetrile, but two other breakdown products of amygdalin—prunasin (which is similar in structure to Laetrile) and benzaldehyde—may also be cancer cell inhibitors. The studies discussed in this summary used either Mexican laetrile/amygdalin or the patented form. In most instances, the generic term “laetrile” will be used in this summary; however, a distinction will be made between the products when necessary.
Laetrile can be administered orally as a pill, or it can be given by injection (intravenous or intramuscular). It is commonly given intravenously over a period of time followed by oral maintenance therapy. The incidence of cyanide poisoning is much higher when laetrile is taken orally  Reviewed in  because intestinal bacteria and some commonly eaten plants contain enzymes (beta-glucosidases) that activate the release of cyanide after laetrile has been ingested. Reviewed in  Relatively little breakdown to yield cyanide occurs when laetrile is injected. Reviewed in  Administration schedules and the length of treatment in animal models and humans vary widely.1Howard-Ruben J, Miller NJ: Unproven methods of cancer management. Part II: Current trends and implications for patient care. Oncol Nurs Forum 11 (1): 67-73, 1984 Jan-Feb.2Curt GA: Unsound methods of cancer treatment. Princ Pract Oncol Updates 4 (12): 1-10, 1990.3Dorr RT, Paxinos J: The current status of laetrile. Ann Intern Med 89 (3): 389-97, 1978.4Calabrese EJ: Possible adverse side effects from treatment with laetrile. Med Hypotheses 5 (9): 1045-9, 1979.5The laetrile controversy. In: Moss RW: The Cancer Industry: The Classic Expose on the Cancer Establishment. Brooklyn, NY: First Equinox Press, 1996, pp 131-52.6Laetrile at Sloan-Kettering: a case study. In: Moss RW: The Cancer Industry: The Classic Expose on the Cancer Establishment. Brooklyn, NY: First Equinox Press, 1996, pp 153-86.7Lerner IJ: Laetrile: a lesson in cancer quackery. CA Cancer J Clin 31 (2): 91-5, 1981 Mar-Apr.8Ellison 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 299 (10): 549-52, 1978.9Moertel CG, Fleming TR, Rubin J, et al.: A clinical trial of amygdalin (Laetrile) in the treatment of human cancer. N Engl J Med 306 (4): 201-6, 1982.10Ross WE: Unconventional cancer therapy. Compr Ther 11 (9): 37-43, 1985.11Lewis JP: Laetrile. West J Med 127 (1): 55-62, 1977.12Unproven methods of cancer management. Laetrile. CA Cancer J Clin 22 (4): 245-50, 1972 Jul-Aug.13Rosen GM, Shorr RI: Laetrile: end play around the FDA. A review of legal developments. Ann Intern Med 90 (3): 418-23, 1979.14Curran WJ: Law-medicine notes. Laetrile for the terminally ill: Supreme Court stops the nonsense. N Engl J Med 302 (11): 619-21, 1980.15Fenselau C, Pallante S, Batzinger RP, et al.: Mandelonitrile beta-glucuronide: synthesis and characterization. Science 198 (4317): 625-7, 1977.16Chandler RF, Anderson LA, Phillipson JD: Laetrile in perspective. Can Pharm J 117 (11): 517-20, 1984.17Newmark J, Brady RO, Grimley PM, et al.: Amygdalin (Laetrile) and prunasin beta-glucosidases: distribution in germ-free rat and in human tumor tissue. Proc Natl Acad Sci U S A 78 (10): 6513-6, 1981.18Rauws AG, Olling M, Timmerman A: The pharmacokinetics of prunasin, a metabolite of amygdalin. J Toxicol Clin Toxicol 19 (8): 851-6, 1982.19Kochi M, Takeuchi S, Mizutani T, et al.: Antitumor activity of benzaldehyde. Cancer Treat Rep 64 (1): 21-3, 1980.20Kochi M, Isono N, Niwayama M, et al.: Antitumor activity of a benzaldehyde derivative. Cancer Treat Rep 69 (5): 533-7, 1985.21Gostomski FE: The effects of amygdalin on the Krebs-2 carcinoma and adult and fetal DUB(ICR) mice. [Abstract] Diss Abstr Int B 39 (5): 2075-B, 1978.22Herbert V: Laetrile: the cult of cyanide. Promoting poison for profit. Am J Clin Nutr 32 (5): 1121-58, 1979.23Viehoever A, Mack H: Bio-chemistry of amygdalin (bitter, cyanogenetic principle from bitter almonds). Am J Pharm 107(Oct): 397-450, 1935.
Amygdalin was first isolated in 1830 by 2 French chemists. Reviewed in  It was used as an anticancer agent in Russia as early as 1845, with positive results reported for the first patient treated. Reviewed in  Its first recorded use in the United States as a treatment for cancer occurred in the early 1920s. Reviewed in  At that time, amygdalin was taken in pill form; however, the formulation was judged too toxic, and the work was abandoned. In the 1950s, a purportedly nontoxic intravenous form of amygdalin was patented as Laetrile. Reviewed in 
Laetrile has been tested on cultured animal cells (cells grown in specialized containers in the laboratory), in whole animals, in xenograft models (tumor cells from one species transplanted onto another species), and in humans to determine whether it has specific anticancer properties (an ability to kill cancer cells more readily than normal cells). As noted previously (General Information), cyanide is believed to be the main cancer-killing ingredient in laetrile. When amygdalin interacts with the enzyme beta-glucosidase or undergoes hydrolysis (breakdown in a reaction with water) in the absence of enzymes, hydrogen cyanide, benzaldehyde, and glucose (sugar) are produced. Reviewed in  Cyanide can also be produced from prunasin, which is a less-than-complete breakdown product of amygdalin. Reviewed in 
Four different theories have been advanced to explain the anticancer activity of laetrile. The first of these incorporates elements of the trophoblastic theory of cancer, a theory that is not widely accepted as an explanation for cancer formation. According to the trophoblastic theory, all cancers arise from primordial germ cells (cells that, under normal circumstances, would give rise to eggs or sperm), some of which become dispersed throughout the body during embryonic development and, therefore, are not confined to the testes or ovaries. The trophoblastic theory also suggests that transformation of primordial germ cells to a cancerous state is normally prevented by enzymes from the pancreas, and that cancers can be destroyed by pancreatic enzyme supplements and treatment with laetrile. Reviewed in  The rationale for laetrile use is the suggestion that malignant cells have higher than normal levels of an enzyme called beta-glucuronidase (which is different from the aforementioned enzyme beta-glucosidase) and that they are deficient in another enzyme called rhodanese (thiosulfate sulfurtransferase). It has been suggested further that laetrile is modified in the liver and that beta-glucuronidase breaks down the modified compound, ultimately producing cyanide. Rhodanese can convert cyanide into the relatively harmless compound thiocyanate. Thus, it has been proposed that cancer cells are more susceptible to the toxic effects of laetrile than normal cells because of an imbalance in these 2 enzymes. Reviewed in  It is important to note that there is no experimental evidence to support the idea that normal tissues and malignant tissues differ substantially in their concentrations of beta-glucuronidase or rhodanese.
The second theory states that cancer cells contain more beta-glucosidase activity than normal cells and, as in the first theory, that they are deficient in rhodanese. Reviewed in  Evidence from laboratory studies demonstrates that this theory cannot be supported. As noted previously, normal cells and cancer cells contain similar amounts of rhodanese. Furthermore, most types of mammalian cells contain only small traces of beta-glucosidase, and this enzyme has not been detected in tumor samples  or in human blood. Without sufficient levels of beta-glucosidase, it is difficult for intravenously administered amygdalin to be broken down into cyanide and other products.
The third theory states that cancer is the result of a metabolic disorder caused by a vitamin deficiency. It states further that laetrile, or “vitamin B-17,” is the missing vitamin needed by the body to restore health. Reviewed in  Experimental evidence indicates that the level of intake of individual vitamins and/or the vitamin status of an organism can influence the development of cancer, but there is no evidence that laetrile is needed for normal metabolism or that it can function as a vitamin in animals or humans. Reviewed in 
The fourth theory suggests that the cyanide released by laetrile has a toxic effect beyond its interference with oxygen utilization by cells. According to this theory, cyanide increases the acid content of tumors and leads to the destruction of lysosomes (compartments inside cells that contain enzymes capable of breaking down other cellular molecules). The injured lysosomes release their contents, thereby killing the cancer cells and arresting tumor growth. Reviewed in  According to this theory, another consequence of lysosome disruption is stimulation of the immune system.1Dorr RT, Paxinos J: The current status of laetrile. Ann Intern Med 89 (3): 389-97, 1978.2Viehoever A, Mack H: Bio-chemistry of amygdalin (bitter, cyanogenetic principle from bitter almonds). Am J Pharm 107(Oct): 397-450, 1935.3The laetrile controversy. In: Moss RW: The Cancer Industry: The Classic Expose on the Cancer Establishment. Brooklyn, NY: First Equinox Press, 1996, pp 131-52.4Laetrile at Sloan-Kettering: a case study. In: Moss RW: The Cancer Industry: The Classic Expose on the Cancer Establishment. Brooklyn, NY: First Equinox Press, 1996, pp 153-86.5Curt GA: Unsound methods of cancer treatment. Princ Pract Oncol Updates 4 (12): 1-10, 1990.6Fenselau C, Pallante S, Batzinger RP, et al.: Mandelonitrile beta-glucuronide: synthesis and characterization. Science 198 (4317): 625-7, 1977.7Chandler RF, Anderson LA, Phillipson JD: Laetrile in perspective. Can Pharm J 117 (11): 517-20, 1984.8Newmark J, Brady RO, Grimley PM, et al.: Amygdalin (Laetrile) and prunasin beta-glucosidases: distribution in germ-free rat and in human tumor tissue. Proc Natl Acad Sci U S A 78 (10): 6513-6, 1981.9Rauws AG, Olling M, Timmerman A: The pharmacokinetics of prunasin, a metabolite of amygdalin. J Toxicol Clin Toxicol 19 (8): 851-6, 1982.10Ross WE: Unconventional cancer therapy. Compr Ther 11 (9): 37-43, 1985.11Ames MM, Moyer TP, Kovach JS, et al.: Pharmacology of amygdalin (laetrile) in cancer patients. Cancer Chemother Pharmacol 6 (1): 51-7, 1981.12Krebs ET Jr, Krebs ET Sr, Beard HH: The unitarian or trophoblastic thesis of cancer. Med Rec 163 (7): 149-74, 1950.13Ellison NM: Unproven methods of cancer therapy. Drug Ther (NY) 10(July): 73-82, 1980.14Navarro MD: The Philippine experience in the early detection and chemotherapy of cancer. St Tomas J Med 25 (3): 125-33, 1970.15Greenberg DM: The case against laetrile: the fraudulent cancer remedy. Cancer 45 (4): 799-807, 1980.16Levi L, French WN, Bickis IJ, et al.: Laetrile: a study of its physicochemical and biochemical properties. Can Med Assoc J 92 (20): 1057-61, 1965.17Cancer Commission of the California Medical Association.: The treatment of cancer with "laetriles". Calif Med 78 (4): 320-26, 1953.18Unproven methods of cancer management. Laetrile. CA Cancer J Clin 22 (4): 245-50, 1972 Jul-Aug.19Navarro MD: Five years experience with laetrile therapy in advanced cancer. Acta Unio Int Contr Cancrum 15(suppl 1): 209-21, 1959.20Morrone JA: Chemotherapy of inoperable cancer: preliminary report of 10 cases treated with laetrile. Exp Med Surg 20: 299-308, 1962.21Gal EM, Fung FH, Greenberg DM: Studies on the biological action of malononitriles, II: distribution of rhodanese (transulfurase) in the tissues of normal and tumor-bearing animals and the effect of malononitriles thereon. Cancer Res 12: 574-79, 1952.22Conchie J, Findlay J, Levvy GA: Mammalian glycosidases: distribution in the body. Biochem J 71 (2): 318-25, 1959.23Herbert V: Laetrile: the cult of cyanide. Promoting poison for profit. Am J Clin Nutr 32 (5): 1121-58, 1979.24Scott PJ: Laetrile and cancer quackery problems. Cancer Forum 5 (2): 93-97, 1981.25Biaglow JE, Durand RE: The enhanced radiation response of an in vitro tumour model by cyanide released from hydrolysed amygdalin. Int J Radiat Biol Relat Stud Phys Chem Med 33 (4): 397-401, 1978.26Lerner IJ: Laetrile: a lesson in cancer quackery. CA Cancer J Clin 31 (2): 91-5, 1981 Mar-Apr.27Lerner IJ: The whys of cancer quackery. Cancer 53 (3 Suppl): 815-9, 1984.28Shils ME, Hermann MG: Unproved dietary claims in the treatment of patients with cancer. Bull N Y Acad Med 58 (3): 323-40, 1982.29Young VR, Newberne PM: Vitamins and cancer prevention: issues and dilemmas. Cancer 47 (5 Suppl): 1226-40, 1981.30Jukes TH: Laetrile struggles. Nature 263 (5578): 543, 1976.
On the basis of standard laboratory tests and animal models used to screen anticancer drugs, there is little evidence to support a specific cancer-killing ability for laetrile. These investigations used numerous cultured cell lines and tumor models, and they explored the following issues: (1) whether laetrile, given alone or in combination with other substances, exhibits anticancer activity of any kind; (2) the toxic effects associated with laetrile treatment; (3) the location of laetrile breakdown in the body and how this breakdown occurs; and (4) the route(s) of excretion for laetrile and its breakdown products.
Animal studies of laetrile have used rodents, dogs, Reviewed in  rabbits, Reviewed in  and a cat. Early work led to the hypothesis that enzymes were necessary to release cyanide from amygdalin. When high levels of these enzymes were present, symptoms of cyanide poisoning were more pronounced. Reviewed in  In two studies sponsored by the National Cancer Institute and published in 1975, various rodent cancers (osteogenic sarcoma, melanoma, carcinosarcoma, lung carcinoma, and leukemia) were transplanted into rats and mice. In both studies, the animals were treated with intraperitoneal injections of amygdalin, with or without the enzyme beta-glucosidase. None of the solid tumors or leukemias investigated responded to amygdalin at any dose tested. No statistically significant increase in animal survival was observed in any of the treatment groups. Similar results were obtained in another study using human breast and colon cancer cells implanted into mice (xenograft models). Amygdalin at every dose level tested produced no response either as a single agent or in combination with beta-glucosidase. It was discovered that animals experienced more side effects when beta-glucosidase was given concurrently (at the same time) with amygdalin, compared with amygdalin alone.
Additional cell culture and animal studies involving more than a dozen other tumor models have been published. In one study, preliminary findings by one of the principal investigators that amygdalin inhibited the growth of primary tumors and the incidence of lung metastases in mice bearing spontaneous (not treatment-induced) mammary adenocarcinomas could not be confirmed. However, positive results were obtained in four studies.
In the first of these studies, amygdalin enhanced the antitumor activity of a combination of enzymes and vitamin A in mice bearing spontaneous mammary adenocarcinomas. The amygdalin was given by intramuscular injection, the vitamin A was administered orally through a feeding tube, and the enzymes were injected into and around tumor masses. No anticancer activity was observed when amygdalin was given alone.
In the second study, white blood cells and prostate cancer specimens were used to investigate the potential of amygdalin to stimulate the immune system. The researchers found that amygdalin caused a statistically significant increase in the ability of a patient’s white blood cells to adhere to his own prostate cancer cells, suggesting some immune system boosting potential for amygdalin.
The third study investigated the ability of amygdalin and beta-glucosidase to indirectly sensitize the hypoxic (oxygen-starved) cells at the center of a tumor to the lethal effects of gamma irradiation. Cells at the periphery (outer edge) of a tumor are more sensitive to gamma irradiation because they are not oxygen-deprived. Radiation kills cells, in part, by splitting molecules, including oxygen molecules, to form free radicals, which are highly reactive chemicals that can damage DNA and other important cellular components. It has been proposed that, by inhibiting oxygen uptake by peripheral tumor cells, more oxygen will diffuse to the hypoxic cells, thereby increasing their sensitivity to radiation. In this study, beta-glucosidase was used to break down amygdalin to release cyanide, with the cyanide inhibiting oxygen uptake by peripheral tumor cells. Presumably, cyanide uptake by interior tumor cells is less than that of cells located at a tumor’s periphery. Spheres of tumor cells created in the laboratory and tumor slices were used in the study. The investigators found that amygdalin and beta-glucosidase could act as indirect radiation sensitizers of hypoxic tumor cells. It should be noted, however, that independent confirmation of this positive finding has not been published in a peer-reviewed scientific journal. A major hurdle in the application of this technique to animals and humans is the development of a method for delivering a sufficient amount of cyanide to tumors without causing substantial systemic or regional toxicity.
In the fourth study, cultured human bladder cancer cells were treated with amygdalin alone or a combination of amygdalin and an antibody that was coupled (chemically) to beta-glucosidase. The target for this antibody was the glycoprotein (a protein with sugar molecules attached) MUC1. Aberrant forms of MUC1 are produced and displayed at high levels on the outside of several types of cancer cells, including bladder cancer cells. In this study, amygdalin alone was not very effective in killing the bladder cancer cells, but its cell-killing ability was 36 times greater in the presence of the antibody-enzyme complex. There are two possible explanations for this increase in cell-killing ability. The first is that antibody-enzyme complexes bound via MUC1 produce high rates of amygdalin breakdown at the cell surface. This breakdown leads to high local production of cyanide, which is quickly taken up by the cells and kills them. The second explanation is that antibody-enzyme complexes bound to the cells are internalized, thereby increasing the intracellular concentration of beta-glucosidase. Increased beta-glucosidase activity inside a cell would result in increased breakdown of amygdalin taken up by it, and increased cyanide production and cell death. These two potential mechanisms are not mutually exclusive. In another experiment, the researchers cultured bladder cancer cells in the presence of human brain tumor cells, which do not express MUC1. When this coculture was treated with amygdalin and the antibody-enzyme complex, the bladder cancer cells were killed selectively. In view of the mechanisms proposed above, this result is not surprising, since the bladder cancer cells and the brain tumor cells in this coculture formed homogeneous colonies (colonies that contained exclusively bladder cancer cells or brain tumor cells). Conceivably, selective killing of some types of human cancer cells might be achievable through application of this method; however, these positive results must be confirmed independently, and the effectiveness of this approach in animal models must be demonstrated before its use in humans can be considered.
The toxicity of laetrile appears to be dependent on the route of administration. Oral administration is associated with much greater toxicity than intravenous, intraperitoneal, or intramuscular injection. Reviewed in  As noted previously (refer to the History section of this summary for more information), most mammalian cells contain only trace amounts of the enzyme beta-glucosidase; however, this enzyme is present in gastrointestinal tract bacteria and in many food plants. Reviewed in  Two studies have specifically examined the role of intestinal bacteria in the breakdown of orally administered amygdalin. In one study, rats bred and raised under germ-free conditions and rats bred and raised under normal conditions were given oral amygdalin. The germ-free rats exhibited no side effects from the compound, and their blood concentrations of cyanide were indistinguishable from those of untreated rats. Many of the rats with normal quantities of intestinal bacteria showed signs of cyanide poisoning (e.g., lethargy and convulsions), and they had high levels of cyanide in their blood. In the second study, rats were either treated or not treated with the antibiotic neomycin before being given oral amygdalin. In this study, urinary excretion of detoxified cyanide (i.e., thiocyanate) was measured. The amount of urinary thiocyanate was 40 times higher in rats that had not been given the antibiotic, indicating that more amygdalin had been broken down in animals with normal amounts of intestinal bacteria. In humans, as in rats, substantial breakdown of amygdalin occurs in the intestines; however, little breakdown of either intravenously or intramuscularly delivered amygdalin occurs in humans, with most of the intact compound eventually excreted in urine.1Gostomski FE: The effects of amygdalin on the Krebs-2 carcinoma and adult and fetal DUB(ICR) mice. [Abstract] Diss Abstr Int B 39 (5): 2075-B, 1978.2Wodinsky I, Swiniarski JK: Antitumor activity of amygdalin MF (NSC-15780) as a single agent and with beta-glucosidase (NSC-128056) on a spectrum of transplantable rodent tumors. Cancer Chemother Rep 59 (5): 939-50, 1975 Sep-Oct.3Laster WR Jr, Schabel FM Jr: Experimental studies of the antitumor activity of amygdalin MF (NSC-15780) alone and in combination with beta-glucosidase (NSC-128056). Cancer Chemother Rep 59 (5): 951-65, 1975 Sep-Oct.4Stock CC, Tarnowski GS, Schmid FA, et al.: Antitumor tests of amygdalin in transplantable animal tumor systems. J Surg Oncol 10 (2): 81-8, 1978.5Menon MM, Bhide SV: Perinatal carcinogenicity of isoniazid (INH) in Swiss mice. J Cancer Res Clin Oncol 105 (3): 258-61, 1983.6Newton GW, Schmidt ES, Lewis JP, et al.: Amygdalin toxicity studies in rats predict chronic cyanide poisoning in humans. West J Med 134 (2): 97-103, 1981.7Hill GJ 2nd, Shine TE, Hill HZ, et al.: Failure of amygdalin to arrest B16 melanoma and BW5147 AKR leukemia. Cancer Res 36 (6): 2102-7, 1976.8Lea MA, Koch MR: Effects of cyanate, thiocyanate, and amygdalin on metabolite uptake in normal and neoplastic tissues of the rat. J Natl Cancer Inst 63 (5): 1279-83, 1979.9Carter JH, McLafferty MA, Goldman P: Role of the gastrointestinal microflora in amygdalin (laetrile)-induced cyanide toxicity. Biochem Pharmacol 29 (3): 301-4, 1980.10Khandekar JD, Edelman H: Studies of amygdalin (laetrile) toxicity in rodents. JAMA 242 (2): 169-71, 1979.11Manner HW, DiSanti SJ, Maggio MI, et al.: Amygdalin, vitamin A and enzyme induced regression of murine mammary adenocarcinomas. J Manipulative Physiol Ther 1 (4): 246-8, 1978.12Ovejera AA, Houchens DP, Barker AD, et al.: Inactivity of DL-amygdalin against human breast and colon tumor xenografts in athymic (nude) mice. Cancer Treat Rep 62 (4): 576-8, 1978.13Lewis JP: Laetrile. West J Med 127 (1): 55-62, 1977.14Schmidt ES, Newton GW, Sanders SM, et al.: Laetrile toxicity studies in dogs. JAMA 239 (10): 943-7, 1978.15Dorr RT, Paxinos J: The current status of laetrile. Ann Intern Med 89 (3): 389-97, 1978.16Levi L, French WN, Bickis IJ, et al.: Laetrile: a study of its physicochemical and biochemical properties. Can Med Assoc J 92 (20): 1057-61, 1965.17Biaglow JE, Durand RE: The enhanced radiation response of an in vitro tumour model by cyanide released from hydrolysed amygdalin. Int J Radiat Biol Relat Stud Phys Chem Med 33 (4): 397-401, 1978.18Bhatti RA, Ablin RJ, Guinan PD: Tumour-associated directed immunity in prostatic cancer: effect of amygdalin. IRCS Med Sci Biochem 9 (1): 19, 1981.19Koeffler HP, Lowe L, Golde DW: Amygdalin (Laetrile): effect on clonogenic cells from human myeloid leukemia cell lines and normal human marrow. Cancer Treat Rep 64 (1): 105-9, 1980.20Syrigos KN, Rowlinson-Busza G, Epenetos AA: In vitro cytotoxicity following specific activation of amygdalin by beta-glucosidase conjugated to a bladder cancer-associated monoclonal antibody. Int J Cancer 78 (6): 712-9, 1998.21Moertel CG, Ames MM, Kovach JS, et al.: A pharmacologic and toxicological study of amygdalin. JAMA 245 (6): 591-4, 1981.22Newmark J, Brady RO, Grimley PM, et al.: Amygdalin (Laetrile) and prunasin beta-glucosidases: distribution in germ-free rat and in human tumor tissue. Proc Natl Acad Sci U S A 78 (10): 6513-6, 1981.23Navarro MD: Five years experience with laetrile therapy in advanced cancer. Acta Unio Int Contr Cancrum 15(suppl 1): 209-21, 1959.24Conchie J, Findlay J, Levvy GA: Mammalian glycosidases: distribution in the body. Biochem J 71 (2): 318-25, 1959.25Herbert V: Laetrile: the cult of cyanide. Promoting poison for profit. Am J Clin Nutr 32 (5): 1121-58, 1979.26Ames MM, Moyer TP, Kovach JS, et al.: Pharmacology of amygdalin (laetrile) in cancer patients. Cancer Chemother Pharmacol 6 (1): 51-7, 1981.27Unproven methods of cancer management. Laetrile. CA Cancer J Clin 22 (4): 245-50, 1972 Jul-Aug.28Shils ME, Hermann MG: Unproved dietary claims in the treatment of patients with cancer. Bull N Y Acad Med 58 (3): 323-40, 1982.29Ames MM, Kovach JS, Flora KP: Initial pharmacologic studies of amygdalin (laetrile) in man. Res Commun Chem Pathol Pharmacol 22 (1): 175-85, 1978.
Laetrile has been used as an anticancer treatment in humans worldwide. Reviewed in  Although many anecdotal reports and case reports are available, findings from only two clinical trials  have been published. No controlled clinical trial (a trial including a comparison group that receives no additional treatment, a placebo, or another treatment) of laetrile has ever been conducted.
Case reports and reports of case series have provided little evidence to support laetrile as an anticancer treatment. Reviewed in  The absence of a uniform documentation of cancer diagnosis, the use of conventional therapies in combination with laetrile, and variations in the dose and duration of laetrile therapy complicate evaluation of the data. In a case series published in 1962, findings from ten patients with various types of metastatic cancer were reported. These patients had been treated with a wide range of doses of intravenous Laetrile (total dose range, 9–133 g). Pain relief (reduction or elimination) was the primary benefit reported. Some objective responses (responses that are measured rather than based on opinion), such as decreased adenopathy (swollen lymph nodes) and decreased tumor size, were noted. Information on prior or concurrent therapy was provided; however, patients were not followed long-term to determine whether the benefits continued after treatment was stopped. Another case series that was published in 1953 included 44 cancer patients and found no evidence of objective response that could be attributed to laetrile. Most patients with reported cancer regression in this series received recent or concurrent radiation therapy or chemotherapy. Thus, it is impossible to determine which treatment produced the positive results.
Benzaldehyde, which is one of laetrile’s breakdown products, has also been tested for anticancer activity in humans. Two clinical series reported a number of responses to benzaldehyde in patients with advanced cancer for whom standard therapy had failed. In one series, 19 complete responses and ten partial responses were reported among 57 patients who had received either oral or rectal beta-cyclodextrin benzaldehyde; however, precise response durations were specified for only two of the patients. Another series by the same investigators used 4,6-benzylidene-alpha-D-glucose, which is an intravenous formulation of benzaldehyde. In this series, seven complete responses and 29 partial responses were reported among 65 patients, with response durations ranging from 1.5 to 27 months. No toxicity was associated with either preparation of benzaldehyde, and it was reported that the responses persisted as long as treatment was continued. Almost all of the patients in these two series had been treated previously with chemotherapy or radiation therapy, but the elapsed time before the initiation of benzaldehyde treatment was not disclosed.
In 1978, the National Cancer Institute (NCI) requested case reports from practitioners who believed their patients had benefitted from laetrile treatment. Ninety-three cases were submitted, and 67 were considered evaluable for response. An expert panel concluded that two of the 67 patients had complete responses and that four others had partial responses while using laetrile. On the basis of these six responses, NCI agreed to sponsor phase I and phase II clinical trials.
The phase I study was designed to test the doses, routes of administration, and the schedule of administration judged representative of those used by laetrile practitioners. The study involved six cancer patients. The investigators found that intravenous and oral amygdalin showed minimal toxicity under the conditions evaluated; however, two patients who ate raw almonds while undergoing oral treatment developed symptoms of cyanide poisoning.
The phase II study was conducted in 1982 and was designed to test the types of cancer that might benefit from laetrile treatment. Most patients had breast, colon, or lung cancer. To be eligible for the trial, patients had to be in good general condition (not totally disabled or near death), and they must not have received any other cancer therapy for at least 1 month before treatment with amygdalin. Amygdalin, evaluated for potency and purity by NCI, was administered intravenously for 21 days, followed by oral maintenance therapy, utilizing doses and procedures similar to those evaluated in the phase I study. Vitamins and pancreatic enzymes were also administered as part of a metabolic therapy program that included dietary changes to restrict the use of caffeine, sugar, meats, dairy products, eggs, and alcohol. A small subset of patients received higher-dose amygdalin therapy and higher doses of some vitamins as part of the trial. Patients were followed until there was definite evidence of cancer progression, elevated blood cyanide levels, or severe clinical deterioration. Among 175 evaluable patients, only one patient met the criteria for response. This patient, who had gastric carcinoma with cervical lymph node metastasis, experienced a partial response that was maintained for 10 weeks while on amygdalin therapy. Fifty-four percent of patients had measurable disease progression at the end of the intravenous course of treatment, and all patients had progression 7 months after completing intravenous therapy. Seven percent of patients reported an improvement in performance status (ability to work or to perform routine daily activities) at some time during therapy, and 20 percent claimed symptomatic relief. In most patients, these benefits did not persist. Blood cyanide levels were not elevated after intravenous amygdalin treatment; however, they were elevated after oral therapy.
Variations in commercial preparations of laetrile from Mexico, the primary supplier, have been documented. Incorrect product labels have been found, and samples contaminated with bacteria and other substances have been identified. When a comparison was made of products manufactured in the United States and Canada, differences in chemical composition were noted, and neither product was effective in killing cultured human cancer cells.1Lewis JP: Laetrile. West J Med 127 (1): 55-62, 1977.2Moertel CG, Fleming TR, Rubin J, et al.: A clinical trial of amygdalin (Laetrile) in the treatment of human cancer. N Engl J Med 306 (4): 201-6, 1982.3Moertel CG, Ames MM, Kovach JS, et al.: A pharmacologic and toxicological study of amygdalin. JAMA 245 (6): 591-4, 1981.4Navarro MD: The Philippine experience in the early detection and chemotherapy of cancer. St Tomas J Med 25 (3): 125-33, 1970.5Ross WE: Unconventional cancer therapy. Compr Ther 11 (9): 37-43, 1985.6Navarro MD: Five years experience with laetrile therapy in advanced cancer. Acta Unio Int Contr Cancrum 15(suppl 1): 209-21, 1959.7Morrone JA: Chemotherapy of inoperable cancer: preliminary report of 10 cases treated with laetrile. Exp Med Surg 20: 299-308, 1962.8Brown WE, Wood CD, Smith AN: Sodium cyanide as a cancer chemotherapeutic agent: laboratory and clinical studies. Am J Obstet Gynecol 80 (5): 907-18, 1960.9Cancer Commission of the California Medical Association.: The treatment of cancer with "laetriles". Calif Med 78 (4): 320-26, 1953.10Kochi M, Takeuchi S, Mizutani T, et al.: Antitumor activity of benzaldehyde. Cancer Treat Rep 64 (1): 21-3, 1980.11Kochi M, Isono N, Niwayama M, et al.: Antitumor activity of a benzaldehyde derivative. Cancer Treat Rep 69 (5): 533-7, 1985.12Newell GR, Ellison NM: Ethics and designs: laetrile trials as an example. Cancer Treat Rep 64 (2-3): 363-5, 1980 Feb-Mar.13Ellison 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 299 (10): 549-52, 1978.14Davignon JP, Trissel LA, Kleinman LM: Pharmaceutical assessment of amygdalin (Laetrile) products. Cancer Treat Rep 62 (1): 99-104, 1978.15Davignon JP: Contaminated laetrile: a health hazard. N Engl J Med 297 (24): 1355-6, 1977.16Levi L, French WN, Bickis IJ, et al.: Laetrile: a study of its physicochemical and biochemical properties. Can Med Assoc J 92 (20): 1057-61, 1965.
The side effects associated with laetrile treatment mirror the symptoms of cyanide poisoning. Cyanide is a neurotoxin that can cause nausea and vomiting, headache, Reviewed in  dizziness, Reviewed in  cyanosis (bluish discoloration of the skin due to oxygen-deprived hemoglobin in the blood), liver damage, hypotension (abnormally low blood pressure), Reviewed in  ptosis (droopy upper eyelid), ataxic neuropathies (difficulty walking due to damaged nerves), fever, Reviewed in  mental confusion, coma, and death. Reviewed in  Oral laetrile causes more severe side effects than injected laetrile. These side effects can be potentiated (increased) by the concurrent administration of raw almonds or crushed fruit pits, by eating fruits and vegetables that contain beta-glucosidase (e.g., celery, peaches, bean sprouts, carrots), Reviewed in  or by taking high doses of vitamin C. Reviewed in 1Howard-Ruben J, Miller NJ: Unproven methods of cancer management. Part II: Current trends and implications for patient care. Oncol Nurs Forum 11 (1): 67-73, 1984 Jan-Feb.2Moertel CG, Fleming TR, Rubin J, et al.: A clinical trial of amygdalin (Laetrile) in the treatment of human cancer. N Engl J Med 306 (4): 201-6, 1982.3Chandler RF, Anderson LA, Phillipson JD: Laetrile in perspective. Can Pharm J 117 (11): 517-20, 1984.4Leor R, Michaeli J, Brezis M, et al.: Laetrile intoxication and hepatic necrosis: a possible association. South Med J 79 (2): 259-60, 1986.5Lee M, Berger HW, Givre HL, et al.: Near fatal laetrile intoxication: complete recovery with supportive treatment. Mt Sinai J Med 49 (4): 305-7, 1982 Jul-Aug.6Navarro MD: Five years experience with laetrile therapy in advanced cancer. Acta Unio Int Contr Cancrum 15(suppl 1): 209-21, 1959.7Dorr RT, Paxinos J: The current status of laetrile. Ann Intern Med 89 (3): 389-97, 1978.8Smith FP, Butler TP, Cohan S, et al.: Laetrile toxicity: a report of two patients. Cancer Treat Rep 62 (1): 169-71, 1978.9Vizel M, Oster MW: Ocular side effects of cancer chemotherapy. Cancer 49 (10): 1999-2002, 1982.10Kalyanaraman UP, Kalyanaraman K, Cullinan SA, et al.: Neuromyopathy of cyanide intoxication due to "laetrile" (amygdalin). A clinicopathologic study. Cancer 51 (11): 2126-33, 1983.11Ames MM, Moyer TP, Kovach JS, et al.: Pharmacology of amygdalin (laetrile) in cancer patients. Cancer Chemother Pharmacol 6 (1): 51-7, 1981.12Moertel CG, Ames MM, Kovach JS, et al.: A pharmacologic and toxicological study of amygdalin. JAMA 245 (6): 591-4, 1981.13Gostomski FE: The effects of amygdalin on the Krebs-2 carcinoma and adult and fetal DUB(ICR) mice. [Abstract] Diss Abstr Int B 39 (5): 2075-B, 1978.14Schmidt ES, Newton GW, Sanders SM, et al.: Laetrile toxicity studies in dogs. JAMA 239 (10): 943-7, 1978.15Herbert V: Laetrile: the cult of cyanide. Promoting poison for profit. Am J Clin Nutr 32 (5): 1121-58, 1979.16Calabrese EJ: Conjoint use of laetrile and megadoses of ascorbic acid in cancer treatment: possible side effects. Med Hypotheses 5 (9): 995-7, 1979.
Summary of the Evidence for Laetrile/Amygdalin
To assist readers in evaluating the results of human studies of complementary and alternative medicine (CAM) treatments for cancer, the strength of the evidence (i.e., the levels of evidence) associated with each type of treatment is provided whenever possible. To qualify for a level of evidence analysis, a study must:
- Be published in a peer-reviewed scientific journal.
- Report on a therapeutic outcome or outcomes, such as tumor response, improvement in survival, or measured improvement in quality of life.
- Describe clinical findings in sufficient detail that a meaningful evaluation can be made.
Separate levels of evidence scores are assigned to qualifying human studies on the basis of statistical strength of the study design and scientific strength of the treatment outcomes (i.e., endpoints) measured. The resulting two scores are then combined to produce an overall score. A table showing the levels of evidence scores for qualifying human studies cited in this summary is presented below. For an explanation of the scores and additional information about levels of evidence analysis of CAM treatments for cancer, refer to Levels of Evidence for Human Studies of Cancer Complementary and Alternative Medicine.Laetrile/Amygdalin Summary: Reference Numbers and the Corresponding Levels of EvidenceReference Number Statistical Strength of Study DesignStrength of Endpoints Measured Combined Score 3iii Nonconsecutive case series Diii Indirect surrogates -- tumor response rate 3iiiDiii3iii Nonconsecutive case series Diii Indirect surrogates -- tumor response rate3iiiDiii3iii Nonconsecutive case series Diii Indirect surrogates -- tumor response rate 3iiiDiii4 Best case series Not applicable4 4 Best case seriesNot applicable44 Best case seriesNot applicable43iii Nonconsecutive case series Diii Indirect surrogates -- tumor response rate 3iiiDiii1Moertel CG, Fleming TR, Rubin J, et al.: A clinical trial of amygdalin (Laetrile) in the treatment of human cancer. N Engl J Med 306 (4): 201-6, 1982.2Kochi M, Takeuchi S, Mizutani T, et al.: Antitumor activity of benzaldehyde. Cancer Treat Rep 64 (1): 21-3, 1980.3Kochi M, Isono N, Niwayama M, et al.: Antitumor activity of a benzaldehyde derivative. Cancer Treat Rep 69 (5): 533-7, 1985.4Cancer Commission of the California Medical Association.: The treatment of cancer with "laetriles". Calif Med 78 (4): 320-26, 1953.5Navarro MD: Five years experience with laetrile therapy in advanced cancer. Acta Unio Int Contr Cancrum 15(suppl 1): 209-21, 1959.6Morrone JA: Chemotherapy of inoperable cancer: preliminary report of 10 cases treated with laetrile. Exp Med Surg 20: 299-308, 1962.7Moertel CG, Ames MM, Kovach JS, et al.: A pharmacologic and toxicological study of amygdalin. JAMA 245 (6): 591-4, 1981.
Changes to This Summary (08/10/2012)
Editorial changes were made to this summary.
This summary is written and maintained by the PDQ Cancer Complementary and Alternative Medicine Editorial Board, which is editorially independent of NCI. The summary reflects an independent review of the literature and does not represent a policy statement of NCI or NIH. More information about summary policies and the role of the PDQ Editorial Boards in maintaining the PDQ summaries can be found on the About This PDQ Summary and PDQ NCI's Comprehensive Cancer Database pages.
About This PDQ Summary
Purpose of This Summary
This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about the use of laetrile/amygdalin in the treatment of people with cancer. It is intended as a resource to inform and assist clinicians who care for cancer patients. It does not provide formal guidelines or recommendations for making health care decisions.
Reviewers and Updates
This summary is reviewed regularly and updated as necessary by the PDQ Cancer Complementary and Alternative Medicine Editorial Board, which is editorially independent of the National Cancer Institute (NCI). The summary reflects an independent review of the literature and does not represent a policy statement of NCI or the National Institutes of Health (NIH).
Board members review recently published articles each month to determine whether an article should:
- be discussed at a meeting,
- be cited with text, or
- replace or update an existing article that is already cited.
Changes to the summaries are made through a consensus process in which Board members evaluate the strength of the evidence in the published articles and determine how the article should be included in the summary.
The lead reviewer for Laetrile/Amygdalin is:
- Jeffrey D. White, MD (National Cancer Institute)
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Levels of Evidence
Some of the reference citations in this summary are accompanied by a level-of-evidence designation. These designations are intended to help readers assess the strength of the evidence supporting the use of specific interventions or approaches. The PDQ Cancer Complementary and Alternative Medicine Editorial Board uses a formal evidence ranking system in developing its level-of-evidence designations.
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National Cancer Institute: PDQ® Laetrile/Amygdalin. Bethesda, MD: National Cancer Institute. Date last modified <MM/DD/YYYY>. Available at: http://cancer.gov/cancertopics/pdq/cam/laetrile/HealthProfessional. Accessed <MM/DD/YYYY>.
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This information was last updated on 2012-08-10