- Laetrile is another name for a chemical called amygdalin. Amygdalin is found in the pits of many fruits, raw nuts, and plants (see Question 1).
- It is believed that the active anticancer ingredient in laetrile is cyanide (see Question 1).
- Laetrile is given by mouth as a pill or by intravenous injection (see Question 4).
- Laetrile has shown little anticancer effect in laboratory studies, animal studies, or human studies (see Question 5 and Question 6).
- The side effects of laetrile are like the symptoms of cyanide poisoning (see Question 7).
- Laetrile is not approved by the U.S. Food and Drug Administration (FDA) (see Question 8).
Questions and Answers About Laetrile/Amygdalin
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 cyanide. Cyanide is believed to be the active cancer-killing ingredient in laetrile. 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, 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 therapy program 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?
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 “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 effects of 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 response when 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.
Other studies have reported a response to amygdalin:
- One study reported tumor response in mice when amygdalin was given with enzymes and vitamin A, but not when given alone.
- A second study reported that amygdalin caused white blood cells to have an immune response against prostate cancer cells.
- A third study treated tumor cells with amygdalin and the enzyme that activates the release of cyanide. This study reported that tumor cells became more sensitive to radiation.
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 tumor size 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:
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.
Changes To This Summary (06/18/2015)
Changes were made to this summary to match those made to the health professional version.
About This PDQ Summary
Physician Data Query (PDQ) is the National Cancer Institute's (NCI's) comprehensive cancer information database. The PDQ database contains summaries of the latest published information on cancer prevention, detection, genetics, treatment, supportive care, and complementary and alternative medicine. Most summaries come in two versions. The health professional versions have detailed information written in technical language. The patient versions are written in easy-to-understand, nontechnical language. Both versions have cancer information that is accurate and up to date and most versions are also available in Spanish.
PDQ is a service of the NCI. The NCI is part of the National Institutes of Health (NIH). NIH is the federal government’s center of biomedical research. The PDQ summaries are based on an independent review of the medical literature. They are not policy statements of the NCI or the NIH.
Purpose of This Summary
This PDQ cancer information summary has current information about the use of laetrile/amygdalin in the treatment of people with cancer. It is meant to inform and help patients, families, and caregivers. It does not give formal guidelines or recommendations for making decisions about health care.
Reviewers and Updates
Editorial Boards write the PDQ cancer information summaries and keep them up to date. These Boards are made up of experts in cancer treatment and other specialties related to cancer. The summaries are reviewed regularly and changes are made when there is new information. The date on each summary ("Date Last Modified") is the date of the most recent change.
The information in this patient summary was taken from the health professional version, which is reviewed regularly and updated as needed, by the PDQ Cancer Complementary and Alternative Medicine Editorial Board.
Clinical Trial Information
A clinical trial is a study to answer a scientific question, such as whether one treatment is better than another. Trials are based on past studies and what has been learned in the laboratory. Each trial answers certain scientific questions in order to find new and better ways to help cancer patients. During treatment clinical trials, information is collected about the effects of a new treatment and how well it works. If a clinical trial shows that a new treatment is better than one currently being used, the new treatment may become "standard." Patients may want to think about taking part in a clinical trial. Some clinical trials are open only to patients who have not started treatment.
Clinical trials are listed in PDQ and can be found online at NCI's website. Many cancer doctors who take part in clinical trials are also listed in PDQ. For more information, call the Cancer Information Service 1-800-4-CANCER (1-800-422-6237).
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The best way to cite this PDQ summary is:
National Cancer Institute: PDQ® Laetrile/Amygdalin. Bethesda, MD: National Cancer Institute. Date last modified <MM/DD/YYYY>. Available at: http://www.cancer.gov/about-cancer/treatment/cam/patient/laetrile-pdq. Accessed <MM/DD/YYYY>.
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General CAM Information
Complementary and alternative medicine (CAM)—also referred to as integrative medicine—includes a broad range of healing philosophies, approaches, and therapies. A therapy is generally called complementary when it is used in addition to conventional treatments; it is often called alternative when it is used instead of conventional treatment. (Conventional treatments are those that are widely accepted and practiced by the mainstream medical community.) Depending on how they are used, some therapies can be considered either complementary or alternative. Complementary and alternative therapies are used in an effort to prevent illness, reduce stress, prevent or reduce side effects and symptoms, or control or cure disease.
Unlike conventional treatments for cancer, complementary and alternative therapies are often not covered by insurance companies. Patients should check with their insurance provider to find out about coverage for complementary and alternative therapies.
Cancer patients considering complementary and alternative therapies should discuss this decision with their doctor, nurse, or pharmacist as they would any therapeutic approach, because some complementary and alternative therapies may interfere with their standard treatment or may be harmful when used with conventional treatment.
Evaluation of CAM Approaches
It is important that the same rigorous scientific evaluation used to assess conventional approaches be used to evaluate CAM therapies. The National Cancer Institute and the National Center for Complementary and Integrative Health (NCCIH) are sponsoring a number of clinical trials (research studies) at medical centers to evaluate CAM therapies for cancer.
Conventional approaches to cancer treatment have generally been studied for safety and effectiveness through a rigorous scientific process that includes clinical trials with large numbers of patients. Less is known about the safety and effectiveness of complementary and alternative methods. Few CAM therapies have undergone rigorous evaluation. A small number of CAM therapies originally considered to be purely alternative approaches are finding a place in cancer treatment—not as cures, but as complementary therapies that may help patients feel better and recover faster. One example is acupuncture. According to a panel of experts at a National Institutes of Health (NIH) in November 1997, acupuncture has been found to be effective in the management of chemotherapy-associated nausea and vomiting and in controlling pain associated with surgery. In contrast, some approaches, such as the use of laetrile, have been studied and found ineffective or potentially harmful.
The NCI Best Case Series Program which was started in 1991, is one way CAM approaches that are being used in practice are being investigated. The program is overseen by the NCI’s Office of Cancer Complementary and Alternative Medicine (OCCAM). Health care professionals who offer alternative cancer therapies submit their patients’ medical records and related materials to OCCAM. OCCAM conducts a critical review of the materials and develops follow-up research strategies for approaches deemed to warrant NCI-initiated research.
Questions to Ask Your Health Care Provider About CAM
When considering complementary and alternative therapies, patients should ask their health care provider the following questions:
- What side effects can be expected?
- What are the risks associated with this therapy?
- Do the known benefits outweigh the risks?
- What benefits can be expected from this therapy?
- Will the therapy interfere with conventional treatment?
- Is this therapy part of a clinical trial?
- If so, who is sponsoring the trial?
- Will the therapy be covered by health insurance?
To Learn More About CAM
National Center for Complementary and Integrative Health (NCCIH)
The National Center for Complementary and Integrative Health (NCCIH) at the National Institutes of Health (NIH) facilitates research and evaluation of complementary and alternative practices, and provides information about a variety of approaches to health professionals and the public.
- NCCIH Clearinghouse
- Post Office Box 7923 Gaithersburg, MD 20898–7923
- Telephone: 1-888-644-6226 (toll free)
- TTY (for deaf and hard of hearing callers): 1-866-464-3615
- E-mail: email@example.com
- Website: https://nccih.nih.gov
CAM on PubMed
NCCIH and the NIH National Library of Medicine (NLM) jointly developed CAM on PubMed, a free and easy-to-use search tool for finding CAM-related journal citations. As a subset of the NLM's PubMed bibliographic database, CAM on PubMed features more than 230,000 references and abstracts for CAM-related articles from scientific journals. This database also provides links to the websites of over 1,800 journals, allowing users to view full-text articles. (A subscription or other fee may be required to access full-text articles.)
Office of Cancer Complementary and Alternative Medicine
The NCI Office of Cancer Complementary and Alternative Medicine (OCCAM) coordinates the activities of the NCI in the area of complementary and alternative medicine (CAM). OCCAM supports CAM cancer research and provides information about cancer-related CAM to health providers and the general public via the NCI website.
National Cancer Institute (NCI) Cancer Information Service
U.S. residents may call the NCI Cancer Information Service toll free at 1-800-4-CANCER (1-800-422-6237) Monday through Friday from 8:00 am to 8:00 pm. A trained Cancer Information Specialist is available to answer your questions.
Food and Drug Administration
The Food and Drug Administration (FDA) regulates drugs and medical devices to ensure that they are safe and effective.
- Food and Drug Administration
- 10903 New Hampshire Avenue
- Silver Spring, MD 20993
- Telephone: 1-888-463-6332 (toll free)
- Website: http://www.fda.gov
Federal Trade Commission
The Federal Trade Commission (FTC) enforces consumer protection laws. Publications available from the FTC include:
- Who Cares: Sources of Information About Health Care Products and Services
- Fraudulent Health Claims: Don’t Be Fooled
- Consumer Response Center
- Federal Trade Commission
- 600 Pennsylvania Avenue, NW
- Washington, DC 20580
- Telephone: 1-877-FTC-HELP (1-877-382-4357) (toll free)
- TTY (for deaf and hard of hearing callers): 202-326-2502
- Website: http://www.ftc.gov