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Laetrile is a chemically modified form of the chemical amygdalin. This compound occurs naturally in many fruit pits and nuts. French chemists first identified it in 1830. They found that when amygdalin breaks down, it produces the poison cyanide.
Vitamin B17 is another name for laetrile, but it is not a vitamin. Some advocates believe cancer results from a vitamin deficiency that laetrile can presumably correct. Opponents think the term was coined to avoid federal drug safety and efficacy requirements.
During the 1800s, doctors tried using amygdalin to treat cancer. It proved too toxic. In the 1950s, a semi-synthetic form, called laetrile, was produced and promoted as a cancer cure. Several theories exist about its anticancer action. In addition to the vitamin theory, some supporters believe an enzyme found primarily in cancer cells, but lacking in healthy cells, breaks down amygdalin. The amygdalin is broken down to cyanide, which then kills the cancer.
Although some promote it as a cure, there is no scientific evidence of its success.
Laetrile gained notoriety during the 1970s, a time when doctors had fewer effective cancer treatments in their arsenal. Chemotherapy side effects were hard to control. Patients began looking for other options. Approximately 75,000 Americans had tried laetrile by 1978. That year, the National Cancer Institute (NCI) reviewed 93 cases submitted by doctors touting laetrile's benefits. Out of those 93 cases, only 6 actually showed benefits of tumor shrinkage.
The NCI then sponsored research to evaluate laetrile. Two of the 6 patients in the first study died of cyanide poisoning after eating almonds. During the second study, patients received an infusion of amygdalin, followed by laetrile pills. Some patients reported feeling better while taking the drug. But cancer progressed in all 175 patients by the end of treatment. The NCI concluded that laetrile did not have any effect on treating cancer.
Two recent reviews of laetrile did not turn up any randomized studies on the drug. Both reviews concluded that laetrile as cancer treatment has no clinical merit.
The US Food and Drug Administration (FDA) has not approved the use of laetrile and has taken action against US companies to halt Internet laetrile sales. It is illegal to bring the drug into the country for personal use because it has not been found to be safe or effective. Anyone who brings laetrile into the country is in violation of US drug laws.
Adverse reactions to laetrile are similar to those that occur with cyanide poisoning. Eating raw almonds or some fruits and vegetables when taking laetrile can increase the risk of having adverse reactions, which may include:
Many cancer patients want to try alternative therapies. Talk with your doctor if you are considering laetrile, looking for a clinical trial, or using other therapies. Herbal remedies can interfere with drugs ordered by your doctor.
It's always best to be open with your doctor about the kind treatment you want.
American Cancer Society
Food and Drug Administration
Beware of online cancer fraud. US Food and Drug Administration website. Available at: http://www.fda.gov/forconsumers/consumerupdates/ucm048383.htm. Updated April 25, 2017. Accessed July 27, 2017.
Laetrile/amygdalin—for health professionals (PDQ®). National Cancer Institute website. Available at: http://www.cancer.gov/cancertopics/pdq/cam/laetrile/HealthProfessional/page2. Updated March 15, 2017. Accessed July 27, 2017.
Milazzo S, Ernst E, et al. Laetrile treatment for cancer. Cochrane Database Syst Rev. 2011;(11):CD005476.
Milazzo S, Lejeune S, et al. Laetrile for cancer: a systematic review of the clinical evidence. Support Care Cancer. 2007;15(6):583-595.
Last reviewed July 2017 by Michael Woods, MD, FAAP Last Updated: 10/15/2013